'rough running' Cylinder 6 Thor p38 MAF?

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Originally Posted by PeterH

Did you use genuine a Bosch sensor, or aftermarket?
I found out the hard way with my thor engine, aftermarket caused all sorts of weird problems, as soon as I replaced those with genuine Bosch and did an adaptive values reset, all came good instantly.
If it were me, I would replace both O2 sensors at the same time, at least that way you know they are both good and starting from a good base point.
Definitely give the MAF a clean, only use a special MAF spray for that, don't use carcy cleaner or something like that.

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Sorry if I am hijacking Alfamale's thread, but we might have the same or similar issues to resolve.

I have noticed the random cold-start misfire is back, and also noticed something else. The system is doing some funny stuff regarding O2 sensors. On my Scangauge I noticed at operating temp on a 30min drive a few days ago that it was going into open loop (usually on trailing throttle) and then back to closed loop. Which in my research may be normal. However I noticed this morning that they are going to closed loop at around 40 degrees coolant temp. That doesn't seem normal to me. I though about 70 degrees was when they switched to closed loop.

I did an adaptive value reset on the Nanocom last time I drove the car. I have a feeling that O2 sensors might be on their way out. I take the point that only genuine Bosch replacements should be used for these parts.

I have some MAF cleaner, will try that first...

OK , I don't know a hell of a lot about Thor but I do know a bit about Motronic and injection in general.

1 The MAF only controls mixture on warm up and in open loop. In closed loop the mixture is entirely controlled by the O2 sensors except when the accelerator is pressed quickly when the TPS richens.
2 It is very unlikely that the MAF could affect one cylinder only.
3 A miss on a single cylinder is most likely to be spark plug, injector or mechanically caused EG a leaking exhaust valve.( which will not show on any sensor)

To me the Op should change the spark plug to another cylinder and see if that causes the miss to shift. Also the coil could be bad or the plug wire. Do not assume that new parts are good. Can the coils be switched around?

If the miss stays on 6 , then shift the injector to another cylinder.

If the miss shifts there is the answer. If the miss does not shift assume a mechanical problem and do a compression test.

Regards PhilipA

I have the same vehicle
Start with basics.
Connect a vacuum gauge as per old school and analyse first to confirm mechanical integrity.
Now inspect for vacuum or exhaust leaks(check the flex joints in the extractor)
Are you losing coolant? Have a look at the top of number 6 piston - is is it steam cleaned?
Look at the short and long term fuel trims - is there a lean command or rich command in the feedback loop.
List the reasons that your fuel trims might be as they are.
Work through those reasons methodically.
Include a thorough inspection all wiring for chaffing or high resistance points on that bank - hands and feel.
Now check ignition - as best you can. Spark tester is useful or for ultimate tool to find someone with oscilloscope to check kV, burn times coil ramping curves, coil switching inputs etc etc
Only now look at input and output sensors such as O2 integrity - and use evidence only to nut it out.
Try not to succumb to being a sensor changer - it will cost much more.

Thought I'd update this a bit.

Found that the RB lead from C0645 (RH o2 Sensor) had pulled out of pin 10 from the plug C0635 (into the ECU).

I now have 2 functioning 02 sensors.

Still logging missfires on cylinder 6 - car sounds smooth though.