My 1989 3.2 Carrera is stalling intermittantly. Here are the facts:

1) Stalls after engine is warm
2) Usually within 10 minutes of starting
3) Will start again withing 1 minute of stall
4) Ignition problem most likely since the Tach shows 0 RPM even if the car is still rolling in gear during stall
5) Allmost never happens when engine is hot
6) Allmost never happens more than once on a single drive
7) Sometimes fails to start after engine is shut off for about a minute
8) Diagnostics show nothing

Thanks

 

I would suggest making absolutely sure that the tach is at zero when the engine stalls and you are decelerating in gear (engine still turning). If so this may be your clue.

The issue could be either lack of spark or fuel/air management. If the engine is still rotating down but the tach falls instantly to zero you could have a problem with the ignition box or the relay that powers the ECM. So next time it stalls pay close attention to what happens and the order that it happens.

Most European cars use a power relay for the engine's computer and one for the fuel pump. Some use one relay for both.

Obvious things to check /maintain. Battery terminals/connections and wires. Are they tight? Are they in good physical order?

 

The engine is definately still turning in gear and the tach reads zero. There is plenty of battery power as no other functions appear to be affected and the starter still cranks as normal. If I wait 30 seconds to 1 minute, it will start up again and run normally. The last time it happened, I was going down hill at about 45 mph. The engine was still turning but no power so the car was slowing down. The tach was at zero and I depressed the clutch to avoid stopping completely. I held the clutch in for about 30 seconds, then I put the shift into 3rd gear and released the clutch and it started right up. Then it ran fine all day.

 

DME relay

 

I agree, it's the first thing I would replace. Look at the terminals carefully. If they look brownish or discolored it would indicate heat. Heat = resistance. If so, use a good electrical contact cleaner (Wurth) and a contact enhancer (Stabilant). These are only available from BMW, Porsche, Audi shops. But you can still buy them over the counter.

 

Thanks for the input, I have a DME relay on order and will replace that first. I will let you know how it goes.

Regards,

 

The DME relay is a good, easy place to start. However, your symptom doesn't sound quite right, you have a weird deal and for that I would replace the cylinder head temp sensor (I will assume that your car is regularly maintained and in a fine state of tune). I've had to do a few sensors to fix problems that had no logical explanation, unfortunately I've never had one produce the negative results that testing is supposed to show. The sensor I speak of screws into the forward facing surface of cyl #3 head, and its wire connects inside the engine compartment near cyl #3 intake manifold. Replacement is straight forward, but tricky, and you need a special socket (or you can make one) to tighten the new sensor. Good luck!

 

I had a similar problem with my 87 back in June. The car ran perfectly and then twice without warnings on different days, the car just quit. Both times, after pulling to the side of the road and checking everthing I could, the car restarted and ran fine. I first tried the DME relay as well as a new fuel filter but no fix. The third time the car quit on me was in my driveway fortunately since this time it would not restart. This time I had to flatbed it to the shop where they diagnosed it as a failed engine control module (ECM) which is the computer that controls everything engine wise. I had the ECM rebuilt and have not had any problems since. The next time the car quits, reach under the drivers seat and tap the computer to see if it comes back to life. This is what my mechanic did to quickly diagnose my problem.

Good luck!!!

 

Well, the DME relay seems to have solved the problem. I pulled the old one out and it felt like something was rattling around inside. I have driven the car 4 times since the new relay without an incident although the problem was intermittent. One thing I did notice was the day after the relay was replaced, I started the car and the revs began to fluctuate dramatically (hunting) between 1000 rpm & 2500 rpm. I also observed that the throttle was very over responsive (touchy). I shut the car off and restarted and it has been fine since. Any ideas?

Thx,

 

I believe that the DME has a "memory." Easily reste by disconnecting the battery so it powers down and will relearn when you start driving, as it appears to have done. I'm sure a DME expert will chime in on this. As far as your DME relay. I mounted mine on some rubber pads to help decrease the vibration damages. Others have been able to repair the solder joints inside and reuse as a spare. I alsways carry a DME relay spare.
regards,
Steve

 

Sounds like the problem I had with my 76 S. It was fixed after replacing the CD unit and ignition coil.
It took months to diagnose the problem.

Anthony

 

"I believe that the DME has a "memory." Easily reste by disconnecting the battery so it powers down and will relearn when you start driving, as it appears to have done. I'm sure a DME expert will chime in on this."

The DME relay DOESN"T have a memory (not a "smart relay") nor does the '84 thru
'89 3.2 DME control units. So dis-connecting and re-connecting of the units has no effect.

Check out this web site (www.systemsc.com) for additional troubleshooting
info on the Diagnostics page.

 

Loren is correct (Hi, Loren!) - no memory in the DME circuit.

Pete

 

I knew someone with more knowledge than I on this subject with ante-up.
regards,
Steve

 

If the fluctuating idle reappears, try having the mixture checked and adjusted, if necessary.