E30 318I M40 Auto Stalling

I have a 1989 318I 2 door Auto that stalls infrequently.

I have replaced the Battery, Spark Plugs, Fuel Filter, Starter recently and Fuel Pump 12 months ago. The fuel filter was extremely filthy. After the car had been stationary for 6 months

The car starts first time. When driving on Highway it cruises extremely well. No loss of power.

On the odd occasion the car will stop. No chugging or stuttering... just lack of power and the engine stops.

The engine will start again on the the first or third try. The issue has become more frequent in the last week. (once per day... usually when coming to or starting from a stop. When the fuel tank is full or near empty.

The car was

Any ideas!

Next time this happens, watch the instruments carefully. If the tachometer drops suddenly to zero, you have a power issue
to the engine computer. If the econometer goes all the way left, it is the computer that cuts the fuel since it does not think
it has any air (air flow meter issue). If it goes to the right, it could be a fuel supply problem.

I would also check the throttle switch. Make sure the throttle is closed with the foot off the throttle. The two leftmost contacts
in the swich connector should be linked at this point. Add some throttle, and check that they are no longer linked, and that
the throttle valve opens. Switch ignition on, and check that the idle control valve vibrates.

Thanks///

Just to add some more information. It did stall whilst slowing down from 100kph or 50mph. just a second and it resumed with no issues. I thought it might be a fuel blockage or similar.

When it stalls - the Alt and Oil lights do not come on. The tacho goes just above Zero. As if the car is coasting.

It did a very small back fire on one occasion when restarting.

I will check the air flow meter issue and the throttle switch.

I will check that the idle control valve vibrates as soon as I can find out where it is.

How do I check to see if there is a power problem to the computer?



Edited 1 time(s). Last edit at 04/13/2015 04:29AM by Kicks.

The idle control valve sits between the engine and the firewall, rather high on the intake side. Looks like a small metal cylinder with a cable connection.

The most common cause of engine computer power issues is a faulty relay under the cover on top of the firewall. There are usually three relays there. You could try to swap the two equal ones, and see if it makes a difference.



Edited 1 time(s). Last edit at 04/13/2015 04:32AM by Ove Kvam.

I checked (disconnected and reconnected) all the suggested connections and relays. Inspected the Fuel pump and relays, fuses etc. All sounded, looked and worked correctly.

Will take it for a drive and post updates.

Drove for 80kms. It stalled once when starting from a stop sign after 30 minutes. It does idle slightly rough at times


This has really got me confused so any assistance is appreciated.

Quote
Kicks
Drove for 80kms. It stalled once when starting from a stop sign after 30 minutes. It does idle slightly rough at times


This has really got me confused so any assistance is appreciated.

It could be an issue with the idle control valve, but the most common cause of rough idle is air leaks causing the
engine to get access to unmetered air. If you have a can of start gas, you could try to spray it on various air hoses
while the engine is idling. If it suddenly revs up, you have found your leak.

There is also one more test that can be done to check that the idle program kick in correctly. My 318i was a manual, where this
is very easy, but I guess it can somehow be done with an automatic as well by manually selecting a low gear.

The trick is to let the car coast at speed, with the RPM dropping slowly. At high RPM, the econometer should show no fuel
consumption (fuel cut). As the RPM gets closer to the 800 RPM idle speed, the engine computer should switch to the idle
program, and start feeding fuel to the engine. I guess it happens around 1200 RPM or so. For this to happen, the computer
needs to get the "no throttle" signal from the throttle switch. It will also start working with the idle control valve to regulate
the air supply to the engine.

Thanks for the info.

Ah the joys of start gas. I can get it in the USA but struggle to find supplier here in OZ.

I will look at that and check for any visible leaks and get back to you.

Quote
Kicks
Thanks for the info.

Ah the joys of start gas. I can get it in the USA but struggle to find supplier here in OZ.

I will look at that and check for any visible leaks and get back to you.

Any gas that is flammable will work. Probably even hair spray!

Do the lights go off when the engine stalls ?

I had such an issue once, caused by a loose wire that was hitting the chassis causing a short. Every time it would stop, I would open the hood and check everything to find nothing. Until one time it happened at night and I found the moving cable by the sparks it was making.

--
A physics truck just turned over outside. There's physics everywhere!

This kind of problems usually routes to bad wiring and electric contacts.
We have too many old plugs and wiring, something may fail intermittently and drive people nuts.

All fuses and relays were checked.
Make sure the ignition wirng is good.
Leaky air or vacuum pipes may cause trouble as well.
Oil dipstick counts as a vacuum leak when removed.

An odd thing, when I first bought the old Mercedes Benz after siting idle for a while, it was plagued with minor electric problems, now most problems cured by itself.

Good luck!

Thanks for all the help.

Checked all the vacuum and electrics... cables, fuses and connections. Most of the vacuum tubes have been previously replaced. Fuses removed checked and reinserted.

Attacked the engine with hairspray. Neighbours thought it strange when I started. Nothing transpired.

Will drive again and keep you posted

Well, I tried everything and the problem still exisits. I will take it to the BMW specialist and see what they come up with.

Have you checked the ground straps for good connection? Take them off, clean the surfaces and reconnect them. Same for the fuse box wiring, any corrosion to spot there?
When checking wiring, don't just check for continuity, also check for short circuits to B+ or ground.

Checked all the Negative connections. Will test again.

Thanks for all your help.. Appreciated. I has been a learning experience