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I did a very extensive engine out service on my 933. Unfortunately I have a rough idle and low power since putting everything back together.
To me it sounds like the car is running on 5 cylinders but I'm not sure about that.
The only fault in the Motronic is "43 - Tank ventilation valve". I do not know if this is related to my problem.
I tried dis- and reconnecting the injectors with the engine running to localize the problem but this was not really conclusive.
Spark plugs and ignition wires are new. Distributer belt is good also.
Injectors have been cleaned in a ultrasound bath. My best idea so far is that one was damaged during the procedure
My next idea is to compare the temperatures on the cylinder exhaust outlets (heat exchanger) with a IR thermometer. I'm not sure how well that will work...
Any ideas on how to troubleshoot would be very welcome!
I would think about what was disturbed during the engine out both from what was replaced, for example, ignition wires, were they properly sequenced and connected, to what connections were broken and reconnected such as vacuum lines, were any left loose and not reconnected. There are lots of root and contributing factors that will not throw or reveal themselves by an OBD Code.
Do you have a list of what was done as a starting point of a discussion?
Andy
Is that the fuel tank ventilation? If so it has a line to the inlet manifold for purging which if disconnected would cause your symptoms.
like Andy says check all your vacuum lines
I had same issue after engine out and traced it back to having the intake tube on wrong (the plastic tube connecting the air intake to the motor). After a full DIY engine and transmission out service with new clutch and flywheel I found a way to screw that up.... hopefully something simple for you too.
Since you have the Repair Manual, you should work through the various test points that can cause "Erratic Idling." See the big chart in the diagnostic section: Test Points 2,3, etc. That's definitely where you want to focus your attention.
I agree! The factory service manual section for DME diagnosis is quite good. Voltmeter and then a ECU/OBD scanner that can read the actual values for the various ECU components is very helpful diagnosing what is in spec and what is not.
07-17-2019, 03:57 PM
Rough idle after engine out service
