Engine cuts out and Bosch service has not solution

Jaggi · 12-02-2008, 05:50 AM

My 1991 964 had hall sensor problems and I have posted a threat some weeks ago.

The car is now at a Bosch service that cannot find and solve the problem.

The engine starts to run fine after a DME reset with the Bosch tool and after the spark plug wires and hall sensor was changed and then cut totally out showing hall sensor, oxygen sensor faults and all warning lights (incl airbag, seat belt warning lights etc.) in the car lighting up. The car restarts after cutting out but has lost idle and cannot be driven because it is impossible to rev it up due to the engine cutting out.
The wiring harness has been replaced and a backup harness to the distributor hall sensor was build to test the wiring to the DME which didn't solve the problem either. The engine was checked for vaccum leaks and other non fuctioning sensors and nothing was detected.
The Bosch shop is not thinking that the engine controler is damaged and wants to change it but I am not sure that I want to buy another one without being sure what my problem is.

I appreciate any feedback what I can do to find the problem.

LARRY SHARP · LARRY SHARP's Garage

Some times multi errors can be traced to bad solder joints in the clock .. almost all systems run thru the clock ..

Don Plumley · Don Plumley's Garage

^ +1 - Good call Larry.

ischmitz · ischmitz's Garage

Quote:

Originally Posted by LARRY SHARP

Some times multi errors can be traced to bad solder joints in the clock .. almost all systems run thru the clock ..

are you serious

...

While it is true that the clock hosts most of the warning lights it can not be the reason for a poor running engine cutting out. Nothing runs "through" the clock. There are lights that have one end connected to +12V and the other goes to the respective control units and/or the central informer. Even with the clock not installed the engine would run just fine. The only system that would be getting upset is the airbag control unit. It senses the missing indicator light and throws up a fault code that needs to be deleted by the PST-2 or similar or by disconnecting the battery.

Back to Jaggi's issues. I remember his previous post and then it sort of got taken over by another guy who subsequently traced his very similar issue down to a bad coil.

For me it still sounds like your DME and the other control units are resetting constantly and one of the reasons for that is electronic interference from the ignition system or poor GND. If you have replaced the plug wires try to run the engine with just one or the other ignitior connected. That way you can isolate a bad coil. Or get a replacement coil pack for test purposes and see if that solves your issue.

When you say Bosch service are you referring to an independent shop with a Bosch logo outside? Not that there is anything wrong with that - we have a couple in town. But I have seen them guessing at electrical and electronic problems before and it scared me. The fact that they don't have access to a loaner DME and suggest you buying one tells me you need to find someone more competent in your area.

Good luck,
Ingo

Jaggi · 12-02-2008, 05:42 PM

Ingo,
thanks for your reply. I have called the independent Bosch service to let them know about the test with the coils. The car is now approx 3 weeks in their shop and they have opened the DME and now want to tell me that they see suspicious solder points. I am not prepared to buy new DME without being sure it is really damaged and I can only agree that I will have to change the Bosch service.
Is there a way to check the DME and why are all warning light going off when the engine cuts out?
Thanks
Jaggi

ischmitz · ischmitz's Garage

Jaggi,

And have they done the one-coil at a time test. If not I would raise hell with them......

Where exactly are you located? I think the easiest would be to swap your DME into a good running car. There is no risk of it damaging anything by doing that. The next step is to swap a known good DME into your car. I would bet it doesn't make a difference.

And I agree that you might have to change your shop. If they don't know how to test a DME they should not open it in the first place. And IF there really are bad joints that can be fixed even though I highly doubt it. Again, PM me, if you need help. I do have tested 964 DME's and can also test yours if required.

Cheers,
Ingo