Welcome! Log In Create A New Profile Recent Messages

Advanced

Detonating 318i M40sad smiley

Posted by Flyboy 
June 01, 2013 03:52PM
Hi Guys
Need your wisdom with regards to my little 318i M40, all of a sudden, out of the blue it has started to detonate under moderate load, WTF????
Isn't there supposed yo be a knock sensor to stop misbehaviour like this?
So here is the low down, motor has 400K on it, and is getting tired now, uses quite a bit of oil, of which I have no doubt it is drinking a fair amount of it, although it is not smoking per se, only a nice big blue puff if you step on the gas after an extended period of trailing throttle, such as coasting down hill, which would indicate valve guides more than rings, the rest is escaping through a dodgy front main crank seal, which can stay as it is until the next cam belt change or engine overhaul, whichever comes first.
Compression is on the low side, specs state service limit between 1000 -1100 Kpa, all four pots range between 925 - 975 Kpa, when measured about 3 months ago, note, there was no detonation at the time.
It does not require a heavy throttle load to detonate, a moderate throttle load will get it pinging and detonating, it does not detonate when the motor is cold, only once it is up to running temp, fuel consumption is normal and has not changed, so I don't see a lean condition being the problem.
She runs fine otherwise, just down on power.
I use the same grade of fuel, as always, and put in at he same garages, so I assume fuel quality can be ruled out.
My thinking is that there may be a build up of carbon due to the oil consumption, that is creating a red hot glowing hot spot, causing the trouble, seeing as that Bosch takes care of the fuelling and the timing.
I am thinking a jug of cold water through the airflow meter to give the internals a bath and get rid of the carbon might sort the problem out, or am I missing something here??
Any ideas on this guys, I really would appreciate your input, I would like to sort the problem before it knocks unwanted ventilation holes in the top of my pistons.

----------------------------------------------------------------------------------------------------------------------------------
E30'S AREN'T BUILT, THEY'RE CAUGHT IN THE WILD!!!



When in doubt, use full throttle,
it may not improve the situation, but it will end the suspence.
June 01, 2013 11:02PM
Cleaning with SeaFoam or some similar chemistry may do some good and even water may help but I am thinking the problem is more to do with the ignition timing. It is computer controlled but for some reason is advancing too much. Perhaps a sensor has failed and prevents correct control . There may be a code in the ECU that would give a clue.

Bob in Everett
June 02, 2013 06:21PM
Or a bad load of gas?
June 03, 2013 01:57PM
Thanks Bob, I really needed that,,,hahahaha :wall: one more electronic gremlin and it is getting a set of 40DCOE Webers, whether it likes it or not.
No Idea how to access codes or interpret them, so strike out there, I would give a kingdom for a case of Seafoam, you lot sure are blessed over that side of the pond.
But I hear what you are saying, any idea which sensor would have timing input. TPS or coolant sensor, maybe?
Been kicking the idea around that it may be the head gasket starting to go bad, mainly because in the morning when the car is cold, it does not do it, bt starts once it has heated up to running temp and been driving a while, sort of like something is opening up on expansion as it gets hot, like a failing spot on the head gasket, no water in the oil or vice versa and no coolant loss, so probably between two cylinders, any thoughts on that?
No Al, been through more than one batch of gas from different garages, no change.

----------------------------------------------------------------------------------------------------------------------------------
E30'S AREN'T BUILT, THEY'RE CAUGHT IN THE WILD!!!



When in doubt, use full throttle,
it may not improve the situation, but it will end the suspence.
June 05, 2013 06:02AM
I never used that sea foam you mention.

My old beat-up Citroen has a carburetor, and shows several symptoms as your BMW, so don't go blaming BOSH for your trouble...
I guess the oil use inside the cylinders is the main cause of all trouble.
Knowing you need the BMW and money shortage (aren't we all?!), do you have access to the electric schematics and can you check all the connectors and sensors on the engine by yourself?
Anything further will need specific equipment, professional help and some money...
:rolleyes:

Good luck, keep us posted!
June 05, 2013 06:28PM
Quote
Jose Pinto
I never used that sea foam you mention.

My old beat-up Citroen has a carburetor, and shows several symptoms as your BMW, so don't go blaming BOSH for your trouble...
I guess the oil use inside the cylinders is the main cause of all trouble.
Knowing you need the BMW and money shortage (aren't we all?!), do you have access to the electric schematics and can you check all the connectors and sensors on the engine by yourself?
Anything further will need specific equipment, professional help and some money...
:rolleyes:

Good luck, keep us posted!

I've got a question about seafoam, what's the consensus on that? I've heard it both ways, "YOU'RE GONNA KILL YOUR E30" and "YOU'RE GONNA REVITALIZE YOUR DYING E30".

Which is it? I've got a can in my garage, never used.
June 05, 2013 09:47PM
Bam, we don't have it here, so like Jose, I have never used it, but I am on a few forums for cars and bikes and I have heard nothing but good things about it, not once have I heard any negative comment, but I am sure the guys will jump in with thier personal experiences.
Jose, all the electrics are good, like your Citroen, she is just getting old and showing her age now.

----------------------------------------------------------------------------------------------------------------------------------
E30'S AREN'T BUILT, THEY'RE CAUGHT IN THE WILD!!!



When in doubt, use full throttle,
it may not improve the situation, but it will end the suspence.
September 09, 2013 01:59PM
My 318i detonated (bacfired ) badly a while back, down on power, turned out to be a partially blocked and dirty fuel filter between the tank and the fuel pump.
September 13, 2013 09:49PM
Hey Gerbrandt,
Long time no see!

How have you been?
February 19, 2014 12:16AM
With your mileage I would have said hot carbon spots, but that doesn't seem to fit in with "all the sudden". Just for fun, get a bottle of fuel injector cleaner, and let your vacuum hose suck it up, but you'll have to moderate pinching the hose to stop the engine from stalling, until you want it to stall, then let it soak for an hour. Then fire up your engine and floor it, you should see some awesome clouds of black smoke!
January 20, 2015 11:28AM
Hi All
Been a while, between computer issues and general life getting in the way, as well as spending all my spare time and cash, rebuilding my faithful Suzuki GS1000G, so I can relieve my faithful 318 from her duty as daily driver and spend some much needed time on her giving her the love she deserves, to bring her back to her former glory.
Her 470 000Km and daily duties with minimal maintenance have taken their toll on her and she is showing it, but now that I can afford to take her off the road for extended periods, work shall begin.
That said, she has been fantastic, never missing a beat.

The misfire turned out to be a worn cam and lifters, once replaced, she ran strong again.

My Suzuki GS1000G "Jennifer" before and after


The offending cam and rockers that caused the misfire.




----------------------------------------------------------------------------------------------------------------------------------
E30'S AREN'T BUILT, THEY'RE CAUGHT IN THE WILD!!!



When in doubt, use full throttle,
it may not improve the situation, but it will end the suspence.
January 20, 2015 12:55PM
Yup, the M40 has self destructing cams and rocker arms. I had mine rebuilt to M43 technology with roller rockers. Too bad it was completely destroyed later by a failing timing belt. Went to M42 after that.
January 26, 2015 02:53PM
Wow! I sure hope the oil filter caught all the metal particles!
Sorry, only registered users may post in this forum.

Click here to login

Online Users

Guests: 7
Record Number of Users: 3 on September 29, 2015
Record Number of Guests: 109 on June 08, 2017