1986 328 loud engine clicking sound and stalling. Diagnosis?

I did not mean to imply these are controlled together the same way, rather pointing out they are the two systems that are in play at start up, and both operate only briefly. Once the car has started, then quite promptly after some controlled delays as noted the other systems govern how the car will idle and run, which is the problem being addressed in this thread. A sticky aav, or leaky cold start injector would affect the post start up phase and hence they are part of the diagnostic logic.

The fact the car starts well is a good sign, something is not working after the brief warm up phase it seems.

 

Haven't tried exactly this, but generally, the throttle response has felt normal at all times, regardless of where the idle screw is. So, immediate and normal-feeling engine RPM increase as throttle is opened.

 

Sudden RPM drop when it kicks in.

 

Any difference if you disconnect the wur heater connection (electrical) ?

 

Update here... tldr: bad coil

I arranged to take it to Auto-Elite in NJ last week. Since it seemed to be in fairly "stable" condition, always starting, and seemingly no worse than when I first noticed the issue (low idle, close to stalling), I was going to drive it out there 16 miles. I started my drive and quickly noticed that there was no power when giving it a lot of throttle. This was very different than what I had experienced on the last drive when the issue first started and I drove it home ok. So, I immediately thought now that it must be running on 4 cylinders and came back home to get it towed instead. The $20/year for GEICO roadside assistance really paid off as they covered 100% of the tow all the way out to the shop I specified.

So, it would appear that all that time I was diagnosing, there really was an issue with ignition and was only running one bank. It's just strange since the drive when I first noticed the low idle I definitely still had full power during the drive and return trip home, 30+ miles. I was close to buying a timing light to check if there was spark on all cylinders but was thrown off by how it felt on its last drive. Apologies to folks here for not fully checking that possible cause. I wonder if it somehow degraded from the first symptom on the drive to where it is now with the coil being full dead.

The mechanic confirmed today over the phone that one of the coils was bad and it was running only one bank. He swapped the two sides to confirm the other bank was firing to confirm it was indeed the coil, which he said is corroded. And, the other one is apparently not in good shape as a piece fell out while he was swapping things around so he's ordering two new coils to put in. Hopefully that gets it back to where it should be as far as running right, then I can have them look at a few other more minor things while its there.

 

Great that you have found the root of the problem! Very surprised that by running on one bank, you did not get the "slow down" light going on, or have fuel and smoke coming out the exhaust when doing your various tests. Must have been intermittent.

"The old swap the coils trick...missed it by that much."

 

First of all, congratulations on finding the problem! Now I will say I told you so. Most "fuel problems" turn out to be ignition problems and coils, sensors and control boxes do not necessarily fail suddenly and all at once.

 

It's running beautifully again now. Just drove it back from the shop. Two new coil/modules for it.

The old coil:
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Where the cable goes in was totally corroded:
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hi Sahn44

what is the PN for the coils. I have a similar issue in my 85QV - also looking at the 328/TR relay connected to the ECU as a remedy.

thanks,

San

 

He replaced the coils and modules that are on top. On my invoice it's 58170102 (coil module) and 115013 (coil). I believe he said that he could only obtain these as combined coil+module together.

 

Thanks.