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Uneven power delivery, they all do that?

Posted by Milo 
September 10, 2011 05:35PM
'87 325e with just over 100K miles (indicated..but I believe it)

It has a few flat spots when running through the rpm range. I'd like it to pull cleanly. Is that too much to ask?

It's done it since day one but it's been down on my fix-it list. I recently replaced the exhaust (cat & tail), plugs and air filter

Oh, and I use 87 octane Costco gas.

Normal teutonic temperament?

Thanks,
Matt

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Matt in Everett, WA

BMW n00b with a 1987 325e
I found that the Turner Motorsport chip helped a lot with that in my 1990iC. It improved the drive ability of the car in city driving immensely. The Eta car may need a different bit of help as the cam is set up for low rpm torque but a call to them might be interesting.

Bob in Everett
rkj
I've had three Etas and they have all run cleanly, and powerfully all the way through the band. Two sticks and one auto. That said I think a chip would help for a stronger run up though.

What are your symptoms exactly?

Rick
I took a drive trying to work up a description of my issue...here goes:

When I hammer the throttle it blows through the range with no problems, during average driving I have a hesitation at 1700rpm that is sometimes worse than others. Its severety seems to depend on throttle openings. Possibly a vaccum issue?

I'm bumping my wheel bearing topic again too, somebody is playing a tuba in my drieveline at random intervals.

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Matt in Everett, WA

BMW n00b with a 1987 325e
rkj
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Milo
I took a drive trying to work up a description of my issue...here goes:

When I hammer the throttle it blows through the range with no problems, during average driving I have a hesitation at 1700rpm that is sometimes worse than others. Its severety seems to depend on throttle openings. Possibly a vaccum issue?

I'm bumping my wheel bearing topic again too, somebody is playing a tuba in my drieveline at random intervals.

Hey Matt

Vacuum leak? E30's are always prone to them maybe, but I would look at your wiper track under that black cover on the AFM. I think we have a sticky for it here somewhere.

Rick
I need a professional...

Paying attention to it the last few days I think it's primarily "loading" when applying throttle after shifting...does that make sense?

Searching for a competent shop to take it to.

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Matt in Everett, WA

BMW n00b with a 1987 325e
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rkj
I would look at your wiper track under that black cover on the AFM. I think we have a sticky for it here somewhere.

See this article: http://www.the944.com/afm.htm

The black plastic cover on the AirFlow Meter is glued down and can be pried off. Just be sure to seal it up properly again with some silicone sealer when you're done.
Might just need injectors cleaned.

Bob in Everett
rkj
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Bob in Everett
Might just need injectors cleaned.

The hot start is usually a good test for that; does it take a longer time (more cranking) to start when it's hot and does it act like a flooded motor when it does kick over???
Haven't had a day off in a couple of weeks so not much progress. I did manage to pry the top off of the AFM and stared at it while scratching myself. confused smiley Google told me that the 5mm allen on the body was a rich/lean adjuster, it was all the way down (clockwise) to the stop...is that bad? I now I should wrap my head around the AFM testing but my brain hurts from trying to figure out stuff at work.

It starts the same hot or cold, not instantly but not bad.

When I quickly feed it gas it bogs out badly, I'm guessing too much gas too quickly. I'm back to my assumption that I need a shop with an exhaust sniffer to diagnose it.

Matt
Hey Bob, would you be willing to drive my car around the block and giving your opinion?

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Matt in Everett, WA

BMW n00b with a 1987 325e
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Milo
Google told me that the 5mm allen on the body was a rich/lean adjuster, it was all the way down (clockwise) to the stop...is that bad? [...] I'm back to my assumption that I need a shop with an exhaust sniffer to diagnose it.

Do NOT mess with any adjustment screws, or you will definitely need an exhaust sniffer to fix it later.

That allen screw adjusts how much air bypasses the flapper plate at idle. In adjusts rich/lean only for idle. You NEED an exhaust sniffer to detect what effect this has. It has no effect on the engine when off idle.

If you've got the plastic cover off the air flow meter, then don't touch anything until you've read and understood the article I linked above. Really the only adjustment you should consider at all is moving the contact points where they slide on the wiper track. Over time the contacts can cut through the substrate, giving uneven readings.

Do NOT try to change any of the calibration settings or spring tensions, despite whatever you read to the contrary on Google.
Thanks Ferdinand, the wiper track looks spotless and everything looks like new inside.

Sometimes even cheapskates have to pay-to-play.

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Matt in Everett, WA

BMW n00b with a 1987 325e
Be glad to take your car for a spin and see how it compares with mine. You might also drive mine around the block for the same comparison.

Bob in Everett
It was great meeting you today and I agree that your symptoms are odd. There is more than one "flat" spot during acceleration. Another thing I thought of besides the injectors is possibly the fuel regulator. If that was a bit erratic in pressure control, it might cause a temporary power loss. Just a thought.

Bob

Bob in Everett
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Bob in Everett
It was great meeting you today and I agree that your symptoms are odd. There is more than one "flat" spot during acceleration. Another thing I thought of besides the injectors is possibly the fuel regulator. If that was a bit erratic in pressure control, it might cause a temporary power loss. Just a thought.

Bob

Thanks Bob, I enjoyed meeting you and driving the Cabrio...So THAT'S what power feels like.

I've got a starting point now, I might not get a chance to work on it for a few days.

Much appreciated Bob, you have a great garage full of cool metal.

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Matt in Everett, WA

BMW n00b with a 1987 325e
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Bob in Everett
It was great meeting you today and I agree that your symptoms are odd. There is more than one "flat" spot during acceleration. Another thing I thought of besides the injectors is possibly the fuel regulator. If that was a bit erratic in pressure control, it might cause a temporary power loss. Just a thought.

Bob


The only thing about that is that the pressure regulator is purely mechanical and fairly simple. I wouldn't think a failure would cause erratic fuel pressure. I might suspect a partially clogged fuel filter first, but even that seems unlikely. Usually fuel issues create very rich or very lean issues that cause even power loss across the entire band, or high/low RPMs. For something to come and go like that I would really suspect a sensor or electrical.

Arbitrary flat spots really sounds like the AFM, but we think that is good, right?
Milo or Bob, does The power loss feel like the loss of a cylinder (power wise), or more than that? Could it be as simple as moisture in the distributor? Or a really bad spark plug wire?Something would generally cause lower power, but given an occasional increase in frequency of failure would cause it to feel "flat"? Or does it feel like an on/off switch of rapid power loss/gain?

...always lurking, rarely posting...
Tyler

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1989 - E30 - M20 - Manual. Approximately 270,000 miles
2000 - E46 - M52TUB28 - Manual. Approximately 110,000 miles

What it felt like to me was like just letting up on the throttle momentarily. I accelerated from about 1500 rpm to about 3500 and it seemed like around 1700 and at 3000 it just stopped accelerating momentarily then resumed.

I had the throttle floored the whole time so the AFM would be reacting to the increasing air flow as the engine accelerated. But the engine seemed to be smooth running. It did not seem to misfire or run rough at all. The "flat" spots seemed to be as slightly different rpm other times I was accelerating.

Is a mystery.

Bob in Everett
What should happen if I disconnect the vacuum line from the fuel pressure regulator? My idle will immediately rise a little (barely noticeable) and over a a minute or so will creep up ~300-500 RPM.

Mostly a mental excrcise trying to wrap my head around a new set of systems and how they all relate.

It sure would be nice to have a car smart enough to throw a code and tell me what's wrong. Thinking is hard.

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Matt in Everett, WA

BMW n00b with a 1987 325e
according to the diagram in my book, and the explanation, the fuel pressure will rise when the vacuum hose is disconnected. The fuel pressure increase will cause more fuel to be passed through the injectors. The engine control would have to increase the air flow to keep the oxygen sensor happy. Might take a few seconds to get it back in regulation.

Did you plug the vacuum line when it was disconnected? Unmetered air into the engine confuses the controller.

Bob in Everett
Progress of the depressing sort...

Decided check fuel pumps:
-The tank pump doesn't come on with the key. No voltage at the pump.
-12V @ #30 on the fuel pump relay but no control voltage on 85 or 86 with the key on.
- When I jump #30 to #87 the pump purrs happily.
-Control voltage comes from MOTRONIC CONTROL UNIT.

[www.armchair.mb.ca]

Sound logical?

Now for the dumb question part (I get one a week). Is the Motronic Control Unit the ECU or some other magic box? Where is it? I know that's two dumb questions...sorry.

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Matt in Everett, WA

BMW n00b with a 1987 325e



Edited 1 time(s). Last edit at 10/16/2011 07:06PM by Milo.
Hi Milo,

The Motronic Control Unit, the DME and the CPU are all terms for the brain that controls the engine.

There is also an Idle Control Module(CPU) for the idle mixture on some of the earlier(pre 1988) cars. So it is important to differentiate between them.

I no longer have my Bentley or Probst manuals but if I remember correctly; the fuel pumps are controlled not only by the ECU but by the fuel pump relay.
If the ECU doesn't actuate the, the main relay and thus fuel pump relay, you don't even get a start.

With the two pump system, it's possible for the car to run and even normally if the main(external) pump is working. The other one is a transfer pump that simply pumps fuel from one side of the tank to the other. If that pump isn't working; I suppose it's possible to have symptoms like you are having but I would think that this would only apply when the tank is at less than half full and not even noticeable with a full tank.
I haven't thought to pay attention if it runs differently with a full tank...never crossed my mind but it does seem to run better sometimes than others.

As an aside my oil change interval readout doesn't work anymore either, I noticed it but never thought much about it until now.

This is probably obvious but the oxygen sensor heater relay doesn't click at the same time the fuel pump relay doesn't click. It's fed by the same output of the ECU.

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Matt in Everett, WA

BMW n00b with a 1987 325e



Edited 1 time(s). Last edit at 10/16/2011 07:34PM by Milo.
And another thing!

My 325e has a build date of 6/07 on the door jamb. My ECU *should* be 0 261 200 154 according to Pelican and others, I've got the earlier 0 261 200 027 ECU in my glove box.

Scratches head.

I need some expertise.

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Matt in Everett, WA

BMW n00b with a 1987 325e
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Milo
And another thing!

My 325e has a build date of 6/07 on the door jamb. My ECU *should* be 0 261 200 154 according to Pelican and others, I've got the earlier 0 261 200 027 ECU in my glove box.

Scratches head.

I need some expertise.

Some other guys can correct me if I'm wrong here, but there few about like 4-8 ECUs for the E30, and they are all compatible with each other. 173 and 154 being the two most common by far. There are some difference between them (I think the stomp test ability is a feature added later), but they should all work. Now, there might be a difference between which ECU matches with a motor. But not having the exact one specified by your VIN does not automatically mean that something is wrong with it.

-----------------------------------------------------------------------------------
1989 - E30 - M20 - Manual. Approximately 270,000 miles
2000 - E46 - M52TUB28 - Manual. Approximately 110,000 miles

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Earendil
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Milo
And another thing!

My 325e has a build date of 6/07 on the door jamb. My ECU *should* be 0 261 200 154 according to Pelican and others, I've got the earlier 0 261 200 027 ECU in my glove box.

Scratches head.

I need some expertise.

Some other guys can correct me if I'm wrong here, but there few about like 4-8 ECUs for the E30, and they are all compatible with each other. 173 and 154 being the two most common by far. There are some difference between them (I think the stomp test ability is a feature added later), but they should all work. Now, there might be a difference between which ECU matches with a motor. But not having the exact one specified by your VIN does not automatically mean that something is wrong with it.

Tyler,

I wish I still had my Bentley and my mind but I have to caution against your logic.
There are incompatibilities between most of the Motronics versions. Some are just non starters while others are A-ok with a bunch in between.

Case in point; we used to have a member here; 'Djumanji'(Andrew Schluckbier) who had a 1988 super eta that someone had put a later model DME into it. He had no end of detonation(pinging) problems, until he replaced it with the proper one.

Some of the DME's were only timing control units and required the ICM(Idle control modules) to work.

I miss my stuff or I could tell you exactly which ECUs were compatible and which were not sad smiley
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Archeo-peteriX


I wish I still had my Bentley and my mind but I have to caution against your logic.

My logic should always be questioned, but in this case I think it was sound. Because most E30 models had were produced with multiple different and BMW compatible ECUs, than just because the ECU in your glovebox doesn't match something like RealOEM doesn't mean it is the wrong ECU.

I did some searching for an ECU E30 compatability list.
I found a list over at PelicanParts.

The summary though, is that the 325e has two compatible ECUs, the 027 (which Milo has) and the 154 which is what his search returned.

Now, I don't know if all the ECUs are forwards compatible, but I know they are backwards compatible. i.e. An older ECU may not work in a newer car, but a newer ECU will work in an older car. In any case though, Milo should probably research the matter to his own satisfaction, especially if he intends on replacing it with something else. In the mean time, the issue is more likely to be something other than the ECU since it is an intermittent problem.

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1989 - E30 - M20 - Manual. Approximately 270,000 miles
2000 - E46 - M52TUB28 - Manual. Approximately 110,000 miles

Matt,
The main pump may only come on for one second when the key is turned on. It waits until the engine starts before it runs continuously.

Bob

Bob in Everett
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Earendil
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Archeo-peteriX


I wish I still had my Bentley and my mind but I have to caution against your logic.

My logic should always be questioned, but in this case I think it was sound. Because most E30 models had were produced with multiple different and BMW compatible ECUs, than just because the ECU in your glovebox doesn't match something like RealOEM doesn't mean it is the wrong ECU.

I did some searching for an ECU E30 compatability list.
I found a list over at PelicanParts.

The summary though, is that the 325e has two compatible ECUs, the 027 (which Milo has) and the 154 which is what his search returned.

Now, I don't know if all the ECUs are forwards compatible, but I know they are backwards compatible. i.e. An older ECU may not work in a newer car, but a newer ECU will work in an older car. In any case though, Milo should probably research the matter to his own satisfaction, especially if he intends on replacing it with something else. In the mean time, the issue is more likely to be something other than the ECU since it is an intermittent problem.

While that list is a good resource; it does have some issues.
Case in point, the '380' module listed for 1987-1991 325i, is and iX...this module was a special intended only for the 1988 super eta with the M20B27 engine. That engine has an 'i' head with and 'e' bottom end and a modified valve train not found in either the 'e' or the 'i' versions.

Yes, the 380 will work in those other engines but there will be driveability issues and emissions issues.

One also has to be careful of crossover models; ie ones that were equipped with one module and a month later with another.
There is a fundamental differnce between the '027' which is a Motronic 1.0 module and the '154' Motronic 1.1 module. The former required and was partnered with the ICM CPU as the idle controller while the latter had the idle control functions built in.

Some modules are forward and backward compatible; but it is important to make sure if that is the case for the individual car.
Milo needs to be very careful in what he selects.
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Bob in Everett
Matt,
The main pump may only come on for one second when the key is turned on. It waits until the engine starts before it runs continuously.

Bob

That is correct; except the shut off time is more like 30 to 90 seconds depending on the year and model of E30.
The proper test is to check it when the engine is running thumbs up
Stepping back from the abyss this morning.

Sorry guys, I got on the wrong track yesterday. Once I jumped the relay to make the pump come on, noticed the power was daisy-chained to both fuel pumps and noted the car ran (which it wouldn't with no power to both fuel pumps) I should have heard a little bell in my head.

I'll get back at it after work.

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Matt in Everett, WA

BMW n00b with a 1987 325e
As to the oil service indictator leds not working, the batteries on the instrument cluster need replacing, minor issue.

alan



Edited 1 time(s). Last edit at 10/17/2011 10:28AM by alanrw.
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alanrw
As to the oil service indictator leds not working, the batteries on the instrument cluster need replacing, minor issue.

alan

When I bought the car the lights were pegged in the"change oil" position. The interweb told me how to short pins together on the diagnostic connector to make it go away...it went away and 2000+ miles later it's still dark. I think I reset it too good.

What did I fry?

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Matt in Everett, WA

BMW n00b with a 1987 325e
Tonights efforts focused on a new fuel filter and cleaning the ICV. The ICV is an older one I bought after my wife broke the connector off the other one helping me with the Bosal exhaust fiasco, it has the adjustment screw on it.

The fuel filter was pretty easy except for the mystery part that Google told me was a pulse reducer for the fuel pump. It's in the garbage now, replaced with a nice piece of fuel hose.

After I got the filter changed I had my daughter start the car while I had my hand on the fuel pump by the filter. No hum or vibration suggesting pumping activity. Is it that quiet or is it dead?

On my second tank of fuel injector cleaner.

I may just shelve this for a while and chase other gremlins, like the passenger window that decided to quit opening. Lights dim when the switch is pushed so I suspect motor issues.

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Matt in Everett, WA

BMW n00b with a 1987 325e
October 18, 2011 10:13PM
If the lights dim, there must be power going to the motor...so the motor is not burned out...yet. Do the lights dim if the window control button is pushed either up or way?

Could be just the regulator is stuck for some reason.

Bob in Everett
rkj
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Milo
Tonights efforts focused on a new fuel filter and cleaning the ICV. The ICV is an older one I bought after my wife broke the connector off the other one helping me with the Bosal exhaust fiasco, it has the adjustment screw on it.

The fuel filter was pretty easy except for the mystery part that Google told me was a pulse reducer for the fuel pump. It's in the garbage now, replaced with a nice piece of fuel hose.

After I got the filter changed I had my daughter start the car while I had my hand on the fuel pump by the filter. No hum or vibration suggesting pumping activity. Is it that quiet or is it dead?

On my second tank of fuel injector cleaner.

I may just shelve this for a while and chase other gremlins, like the passenger window that decided to quit opening. Lights dim when the switch is pushed so I suspect motor issues.

Are you wondering if the pump is putting out Matt?

Yes, you can do away with the pulse valve but I still think they're good things. Too bad the dam things are so expensive!

Rick
Last night I unhooked the tank pump and jumped the fuel pump relay again. The pump by the filter spun up nicely...so, both pumps are working but the pressure is unknown because I haven't figured out how to do it yet.

I'm waiting for an opportunity to shut the car down for a few days and get the injectors cleaned. As of now I need it to haul kids around. Next week, maybe.

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Matt in Everett, WA

BMW n00b with a 1987 325e
rkj
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Milo
Last night I unhooked the tank pump and jumped the fuel pump relay again. The pump by the filter spun up nicely...so, both pumps are working but the pressure is unknown because I haven't figured out how to do it yet.

I'm waiting for an opportunity to shut the car down for a few days and get the injectors cleaned. As of now I need it to haul kids around. Next week, maybe.

You'll need a gauge set-up, that I think is not expensive. I got mine at napa and I plumbed it up to my needs. I think you could probably make something up too. If you want I can post pictures of what I have and I can tell you how I do the tests; all very simple.

On eta cars I usually test the pumps independently (on twin pump cars) just to make sure both are on line and then test the system as a whole...

Rick
FIXT...Much better anyway.

I finally brought it to Conaway Motors (great shop BTW) and they put it on their "decarbonator" that cleaned the carbon deposits off of the intake valves. They also adjusted the screw on the AFM with the volt meter attached...it was way off.

It revs much cleaner and seems to pull harder, I'll know more as I put more miles on it.

Thanks for the help all!

Matt

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Matt in Everett, WA

BMW n00b with a 1987 325e
rkj
Quote
Milo
FIXT...Much better anyway.

I finally brought it to Conaway Motors (great shop BTW) and they put it on their "decarbonator" that cleaned the carbon deposits off of the intake valves. They also adjusted the screw on the AFM with the volt meter attached...it was way off.

It revs much cleaner and seems to pull harder, I'll know more as I put more miles on it.

Thanks for the help all!

Matt

Good news, I've never adjusted that screw on the afm. Wonder what the procedure is?

Cheers, Rick
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Milo
FIXT...Much better anyway.

I finally brought it to Conaway Motors (great shop BTW) and they put it on their "decarbonator" that cleaned the carbon deposits off of the intake valves. They also adjusted the screw on the AFM with the volt meter attached...it was way off.

It revs much cleaner and seems to pull harder, I'll know more as I put more miles on it.

Thanks for the help all!

Matt

That was totally going to be our next suggestion...


Actually, tribal knowledge says to never touch the AFM screw. They are calibrated by BMW and shouldn't be changed. That said, if it's off, and you have the test equipment to prove it, I don't see why adjusting it would be all that bad. Glad you got it all sorted out!

-----------------------------------------------------------------------------------
1989 - E30 - M20 - Manual. Approximately 270,000 miles
2000 - E46 - M52TUB28 - Manual. Approximately 110,000 miles

Over on the right rear corner under the hood is the connector going down to the O2 sensor, probing into the rear of the connector with voltmeter leads the smart guy found .8V (rich). He adjusted the screw until it was .5V.

My adjustment screw was all the way in, not the way it's supposed to be I'm sure.

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Matt in Everett, WA

BMW n00b with a 1987 325e
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rkj
Quote
Milo
FIXT...Much better anyway.

I finally brought it to Conaway Motors (great shop BTW) and they put it on their "decarbonator" that cleaned the carbon deposits off of the intake valves. They also adjusted the screw on the AFM with the volt meter attached...it was way off.

It revs much cleaner and seems to pull harder, I'll know more as I put more miles on it.

Thanks for the help all!

Matt

Good news, I've never adjusted that screw on the afm. Wonder what the procedure is?

Cheers, Rick

Well, since it is only there to adjust the bypass air during idle; the only way to properly adjust it is with an exhaust analyzer. It's main purpose is to reduce CO emissions at idle. I doubt very much that using a voltmeter will get it very close to being correct since the engine is long since new from the factory where the screw was set originally...and it has no electrical components eye popping smiley

Smoke and mirrors sad smiley
rkj
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Archeo-peteriX
Quote
rkj
Quote
Milo
FIXT...Much better anyway.

I finally brought it to Conaway Motors (great shop BTW) and they put it on their "decarbonator" that cleaned the carbon deposits off of the intake valves. They also adjusted the screw on the AFM with the volt meter attached...it was way off.

It revs much cleaner and seems to pull harder, I'll know more as I put more miles on it.

Thanks for the help all!

Matt

Good news, I've never adjusted that screw on the afm. Wonder what the procedure is?

Cheers, Rick

Well, since it is only there to adjust the bypass air during idle; the only way to properly adjust it is with an exhaust analyzer. It's main purpose is to reduce CO emissions at idle. I doubt very much that using a voltmeter will get it very close to being correct since the engine is long since new from the factory where the screw was set originally...and it has no electrical components eye popping smiley

Smoke and mirrors sad smiley

I hate it when He does that!

Just when you think you've made some headway, Peter steps in with the skinny... :bow:
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rkj
Quote
Archeo-peteriX
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rkj
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Milo
FIXT...Much better anyway.

I finally brought it to Conaway Motors (great shop BTW) and they put it on their "decarbonator" that cleaned the carbon deposits off of the intake valves. They also adjusted the screw on the AFM with the volt meter attached...it was way off.

It revs much cleaner and seems to pull harder, I'll know more as I put more miles on it.

Thanks for the help all!

Matt

Good news, I've never adjusted that screw on the afm. Wonder what the procedure is?

Cheers, Rick

Well, since it is only there to adjust the bypass air during idle; the only way to properly adjust it is with an exhaust analyzer. It's main purpose is to reduce CO emissions at idle. I doubt very much that using a voltmeter will get it very close to being correct since the engine is long since new from the factory where the screw was set originally...and it has no electrical components eye popping smiley

Smoke and mirrors sad smiley

I hate it when He does that!

Just when you think you've made some headway, Peter steps in with the skinny... :bow:

But from what Milo said, they only adjusted the AFM and decarbed the intake valves, and this DID produce progress. I suppose he could have had so much carb build up that it was making spuradic power. But it strikes me that the AFM if completely out of whack would be a stronger suspect.
So even if they couldn't adjust the AFM perfectly, I'd guess that they at least improved it. Especially if the screw was indeed all the way down. Probably some punk previous owner started messing with it.
Milo, how long have you owned the car?

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1989 - E30 - M20 - Manual. Approximately 270,000 miles
2000 - E46 - M52TUB28 - Manual. Approximately 110,000 miles

I'm new to this so I don't want to sound like I know what I'm talking about but...here goes.

Don't all the sensor inputs rely on changing resistance on a known volotage?
Isn't the oxygen sensor an exhaust analyzer of a sort that changes resistance as the oxygen level changes.

I haven't spent a lot of time driving (motorcycle commuter) but I can say that the low speed response is much crisper. It still pulls unevenly when run through the range but I've never driven a well-running e to compare with.

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Matt in Everett, WA

BMW n00b with a 1987 325e
rkj
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Milo
I'm new to this so I don't want to sound like I know what I'm talking about but...here goes.

Don't all the sensor inputs rely on changing resistance on a known volotage?
Isn't the oxygen sensor an exhaust analyzer of a sort that changes resistance as the oxygen level changes.

I haven't spent a lot of time driving (motorcycle commuter) but I can say that the low speed response is much crisper. It still pulls unevenly when run through the range but I've never driven a well-running e to compare with.

I'm only going by what I've read here for years but it's my understanding the 02 sensor does not influence things much. Peter?
I am glad you qualified that "never driven" statement since my "i" that you drove runs pretty well. There is a guy at my work that has an "e" that has more than twice the miles yours has and it is still going strong.

Bob in Everett
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Earendil
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rkj
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Archeo-peteriX
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rkj
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Milo
FIXT...Much better anyway.

I finally brought it to Conaway Motors (great shop BTW) and they put it on their "decarbonator" that cleaned the carbon deposits off of the intake valves. They also adjusted the screw on the AFM with the volt meter attached...it was way off.

It revs much cleaner and seems to pull harder, I'll know more as I put more miles on it.

Thanks for the help all!

Matt

The decarb may well have been the defining factor...but the AFM screw is only in effect at idle. Once the AFM flap opens; it makes no difference where the screw is set because the bypass is being bypassed.

Adjusting the screw and getting changes in the O2 sensor at idle will have No effect on the problems Milo was experiencing at various throttle openings.

At best. his engine is now emitting far less CO than it was.

Time will tell if the decarb has done the trick.

I'm really not surprised at the nonsense some 'mechanics' try to fpoist off on folks they think are ignorant :wall:

Good news, I've never adjusted that screw on the afm. Wonder what the procedure is?

Cheers, Rick

Well, since it is only there to adjust the bypass air during idle; the only way to properly adjust it is with an exhaust analyzer. It's main purpose is to reduce CO emissions at idle. I doubt very much that using a voltmeter will get it very close to being correct since the engine is long since new from the factory where the screw was set originally...and it has no electrical components eye popping smiley

Smoke and mirrors sad smiley

I hate it when He does that!

Just when you think you've made some headway, Peter steps in with the skinny... :bow:

But from what Milo said, they only adjusted the AFM and decarbed the intake valves, and this DID produce progress. I suppose he could have had so much carb build up that it was making spuradic power. But it strikes me that the AFM if completely out of whack would be a stronger suspect.
So even if they couldn't adjust the AFM perfectly, I'd guess that they at least improved it. Especially if the screw was indeed all the way down. Probably some punk previous owner started messing with it.
Milo, how long have you owned the car?
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rkj
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Milo
I'm new to this so I don't want to sound like I know what I'm talking about but...here goes.

Don't all the sensor inputs rely on changing resistance on a known voltage?
Isn't the oxygen sensor an exhaust analyzer of a sort that changes resistance as the oxygen level changes.

I haven't spent a lot of time driving (motorcycle commuter) but I can say that the low speed response is much crisper. It still pulls unevenly when run through the range but I've never driven a well-running e to compare with.

I'm only going by what I've read here for years but it's my understanding the 02 sensor does not influence things much. Peter?

Generally speaking; the O2 sensor only helps to keep emissions within spec. Ultimate engine performance is only affected at idle if the O2 sensor goes bad.
This is most easily tested by unplugging the O2 sensor and running the car for a few days. If performance improves or gets really bad, then the sensor is faulty. In the case of improved performance; it was sending wrong info to the Motronics system. If it gets really bad; it means the sensor is working but masking bigger problems.

So, as you say 'Don't all the sensor inputs rely on changing resistance on a known voltage'...and that applies hear as well smileys with beer
E30 era 02 sensors give you a voltage. It switches from one level to another when going from lean to rich. (they can only tell if the car is running lean or rich)

More recent cars will have wideband sensors that can actually tell the computer how rich or how lean they are running.
Correct, and the newer ones also work with the OBD2 system and they have a second O2 sensor after the catalytic converter.

The E30 only has the single bipolar O2 sensor.
rkj
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Archeo-peteriX
Correct, and the newer ones also work with the OBD2 system and they have a second O2 sensor after the catalytic converter.

The E30 only has the single bipolar O2 sensor.


The things I still learn here thumbs up
Is this the Coolant Temperature Sensor on a 325e? If it is I think I found my problem, reading 86 ohms at ~100 degrees which is out of range (I think, my Bently is at work)



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Matt in Everett, WA

BMW n00b with a 1987 325e
The Bentley says at 68F 2100-2900 ohms. at 176F 270-400 ohms.

There are two of them though. One for the gauge and the light colored one for the computer.

Bob in Everett
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