Limp

So the BEW in the Jeep has been running great until today.
I believe it is in limp mode but no fault codes are showing on the VCDS.
I also disconnected the battery for a few minutes and that did not help.
Is there anything I can look for?
It only gets about 1/4 throttle and then goes flat.
I got it home on the highway but hills were a bugger.
All the sensors look good and I would expect a fault code from a faulty one?

So some online info suggested the MAF sensor. I disconnected it and the Jeep ran better which points to a bad sensor BUT I reconnected the MAF and its back to running great.
Never dealt with a MAF sensor before, can they come and go?

evguy1 said:

So some online info suggested the MAF sensor. I disconnected it and the Jeep ran better which points to a bad sensor BUT I reconnected the MAF and its back to running great.
Never dealt with a MAF sensor before, can they come and go?

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My experience is that MAF sensors go bad over time and that doesn't lead to decent performance or fuel economy. I always recommend people get the MAF tuned out of the ECU software because of this - it leads to a simpler and cleaner install and isn't really necessary when you already have EGR deleted unless you are looking for every Nm of torque possible in your tune and you still want to keep the smoke at bay.

However, I would check the simpler stuff first - have you checked for fuel and air restrictions? When my fuel pump was starting to go on my Ranger it behaved very sluggishly as it was underfulled - no DTCs were generated.

I actually did have it deleted and had so much black smoke that Mark (Malone) suggested adding the MAF.
The Jeep is running well again today, all I did was unplug it and it ran better and then plugged it back in and it ran great.
The fact that unplugging it made the Jeep run better indicates a bad MAF from what I have read online. The fact that it ran great after plugging the MAF back in is the puzzling part and I'm sure it will come back to bite me sometime soon when least expected or wanted.

There's not been a huge difference in smoke in my MAP based tune vs. MAF. There is a map in the ECU for MAP based smoke limiting (IQ vs. MAP), and once it is dialed in there should be no issue with excessive smoke. Mark could adjust this.

When it's hot out I start to have slightly more smoke at tip in - but there is an additional temp compensation map I could play with to reduce that.

I understand the arguments for why MAF based smoke limiting is superior in theory, however in practice it has not been a noticeable difference in smoke/performance. It sure has been easier to plumb the intake though, and nice to not have to deal with a fragile and expensive sensor I don't need.

Skoda Fabia RS runs a MAP based smoke limiter in the stock tune.

In terms of unplugging and re-plugging your MAF - sure sounds like it could be corrosion on either side of the plug - maybe consider a dab of dielectric grease in there after some contact cleaner?

Did you clear the code after plugging the MAF back in? ME7 on the gas motors will ignore the MAF completely if it it has a stored code for it being faulty and only starts using it again when you clear the code. Not sure if the diesels behave the same?