'rough running' Cylinder 6 Thor p38 MAF?

[AlfaMale]

Hi guys,

My nanocom is indicating that I'm getting rough running on several cylinders but its more apparent on cylinder 6. Cylinder 6 is also persistently logging misfires and throwing error codes (p0306). I'm also getting a p1319 code. I have also got various lambda sensor error codes and other misfire codes which come and go.

The car is not audibly misfiring and seems to drive ok

Replaced so far:

Plugs
leads
coil packs

The nanocom is also suggesting outrageous MAF readings, in the range of >24 g/s at idle. These readings rise in proportion to the engine revs.
My understanding of engine sensors (what each does, how they interact), fuel trims etc is still somewhat limited. Does anyone have readouts of a properly running engine?

Is it possible that a faulty MAF could effect a single cylinder? I've attached the readout of my nancom sitting in my driveway after a spin around the block.Any suggestions on what to try next?

Cheers

[biggin]

It seems to me that your MAF reading is low, even for idle. I reckon your O2 sensors are looking good given your fuel trim numbers.
I’d be replacing the MAF and doing an adaptive reset.

[AlfaMale]

It seems to me that your MAF reading is low, even for idle. I reckon your O2 sensors are looking good given your fuel trim numbers.
I’d be replacing the MAF and doing an adaptive reset.

Thanks Biggin, I had another look this morning and I think the O2 sensor for bank 2 is faulty. 1 02 sensor is fluctuating between .1 and .9 (which I understand is how they work) while 2 sits at about .4. I can't imagine that's the solution to rough running in a specific cylinder but it certainly can't be helping.

[biggin]

It’s true what you say about the O2 sensors operation.
It does seem that #2 is faulty. However it is strange that both your fuel trims are close to 1.00.
When I had problems with my sensor, trim on the bad side was around 1.40.
Have you tried an adaptive reset? It won’t hurt.

[PeterH]

+1 on the adaptive values reset as a first step.
Get some special MAF cleaner spray and give that a clean up too.
The MAF would not affect a single cylinder, it would affect all of them.
I would also pull the plugs and have a look, see if they are carboned up and all black, which would indicate overfuelling.
Check both sides to make sure it's not just one bank affected.
Let us know how that goes.
Cheers, Pete.

[AlfaMale]

So I've replaced the dodgy O2 Sensor and reset the adaptive fuel values. The following has happened.

It is still 'running rough' on several cylinders but particularly Cylinder 6. :(
It is no longer clocking up 'misfires' at an alarming rate but still logs one or two. :)

HOWEVER

The voltage for the new 02 sensor seems to have remained at approx .45 rather than fluctuating like the other. I am also still getting lambda sensor faults for the replaced 02 sensor. (p1000 and p0155)

Pulled the sparkplugs and nothing seems too weird there.

I have not yet done anything with the MAF so will try cleaning that next. Could I draw attention to the readings I'm getting from the MAF in the original post. The Nanoncom reads in g/s right? As i understand a correct idle reading should be about 6 g/s and mine is reading 20 g/s? Has anyone experienced weirdness with the units the nanocom measures in? It would seem my readings would make sense at kg/h rather than g/s

[4X4V8]

I have just driven my Thor P38 1/2hr and plugged in the Nanocom.
(I have have random misfires cyl 1, less than silken idle and I thought I noticed an increase in fuel consumption last long run recently.

My Nanocom doesn't show 'g/s' in the readout like yours does - does your Nanocom have the latest update?
It's a bit confusing because I just checked Blackbox Solutions and it says the MAF reading is in kg/h. My Nanocom just says 'MAF Sensor' and the reading.

My MAF at '27' is reading similar to yours. From the little I've read, this should be more like '20'.

Most other outputs are also similar to yours. Some are a bit out, still researching. No fault codes present though.

I've tried to post pics from the Nanocom but having problems uploading. Will try again later.

Sorry I'm not of much help here....

[AlfaMale]

I have just driven my Thor P38 1/2hr and plugged in the Nanocom.
(I have have random misfires cyl 1, less than silken idle and I thought I noticed an increase in fuel consumption last long run recently.

My Nanocom doesn't show 'g/s' in the readout like yours does - does your Nanocom have the latest update?
It's a bit confusing because I just checked Blackbox Solutions and it says the MAF reading is in kg/h. My Nanocom just says 'MAF Sensor' and the reading.

My MAF at '27' is reading similar to yours. From the little I've read, this should be more like '20'.

Most other outputs are also similar to yours. Some are a bit out, still researching. No fault codes present though.

I've tried to post pics from the Nanocom but having problems uploading. Will try again later.

Sorry I'm not of much help here....


Thanks so much for that! That is excellent information. Sorry you’re having similar problems. I’ve got my car booked into get ball joints done in a couple of weeks time so I’ll ask the mechanic if he has any thoughts.

[4X4V8]

Here are my Nanocom readings. I was waiting for my wife at the shops so taken in a bit of a hurry. Idling in Park with a/c on. Not very scientific sorry, but at least some indication.

From my reading last night both your and my MAF readings are too high (assuming that they are both in kg/h as Blackbox Solutions website suggest they are, with latest software update I presume, which I think my Nanocom has; but your reading suggests grams/sec).
Idle trim at around 1.48 seems too high also but I need to check that's actually the case.

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[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.

[4X4V8]

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.

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...

[PhilipA]

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

[peter51]

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.

[AlfaMale]

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.