1989 930 3.2 engine run over after switch off

[thebo21]

Recently the car develops the engine run over after switch off intermittently. Usually after after engine warm/a few miles drive. After searching the forum, I only found the thread with ignition delay relay on 930 Turbo which seems not related to my case.

It is the engine running roughly/jerky after the key switch off. Not the kind of delay to burn the fuel out as I search the forum. As I uploaded the clip;

https://youtu.be/RsurPz2YcVw

All the vacuum hoses checked with no leakage/breakage/lose.
A good known key switch was replaced but still run over intermittently.

Anywhere to start the diagnosis? Thank you.

[flat6pilot]

That seems like it's dieseling. ?? Could it be a bad/dirty injector letting fuel by for a moment?

[thebo21]

Originally Posted by flat6pilot

That seems like it's dieseling. ?? Could it be a bad/dirty injector letting fuel by for a moment?

I first thought that the leaky injectors were the cause. After took all injectors to check, they are all fine. No leak/drip.

[proporsche]

what is your fuel mix set up C/O? with the oxy sensor disconnected and measuring in front of the catalyst?

Ivan

[thebo21]

Originally Posted by proporsche

what is your fuel mix set up C/O? with the oxy sensor disconnected and measuring in front of the catalyst?

Ivan

I do not have the CO meter so I never try adjusting the mixture at the air flow meter. The engine starts fine and drives normally. Only the dieseling intermittently (maybe 2-3 times out of 10 times).

[mb911]

Can you clarify as a 930 engine is a 3.3 did you put a 3.2 in it? 2 different fuel injection systems 1 cis the other efi

[Lyle O]

Any chance you have a solid-state DME relay (assuming you have Motronic / 3.2)?

[thebo21]

Originally Posted by Lyle O

Any chance you have a solid-state DME relay (assuming you have Motronic / 3.2)?

Repaced the brand new DME relay yesterday but the problem persists.

[thebo21]

Originally Posted by mb911

Can you clarify as a 930 engine is a 3.3 did you put a 3.2 in it? 2 different fuel injection systems 1 cis the other efi

Yes, the engine is 3.2 with motronic.

New plugs (factory spec).
All the vacuum hoses checked with no leaks.
Throttle valve, idle air control valve, and air flow meter cleaned.
Brand new DME relay underseat replaced.

Thank you.