The "check engine light" came on yesterday and I took it to the dealer where they found an error code for the M.A.F. sensor. They couldn't find a problem so they reset it and sent me on my way to see if it happens again. It did shortly after and I'm out of town now for a few days with it.

I did just put it back on the road after winter storage, and filled the tank the day before the C.E.L. illuminated, and wondering if condensation in my tank from storage or from the gas station could cause this condition. As I got near the dealer I felt an occassional jerking under throttle, but prior to that nothing that felt off. Could bad gas throw a M.A.F. code?

Bruce

 

I think I was a victim of bad gas and my car did not throw any hard codes, could of have thrown a soft code though. The good news is the dealership saw the code and now that it was duplicated they probably just need to change out the maf. It will be interesting to see when this tank is empty if the code is thrown after the next fill up.

 

The MAF is upstream of any injectors, so fuel should not be an issue.
Can be related to dirt in the intake so check your filter. You said it was in storage, so make sure you dont have something like a mouse nest in there somewhere (Dont laugh, I have seen it happen several times on other cars....)

Vince
BTW if a nest were found, read up on the Hanta(sp?) Virus before cleaning it up...

 

In the meantime you could throw in some gasline antifreeze because it mixes with water and lets it run through the system.

 

Thank you gents. I will do as suggested, and I agree that you wouldn't think gas quality would have a bearing on the MAF sensor. I don't know what the code was, or if it covered more than the MAF, and the odd jerking feels like it could be water running through...or ECU knock response triggered by an oxygen sensor registering bad air/fuel ratio from a faulty MAF! I'll report findings. Thanks again.

Bruce

 

Food for thought...

Throttle response is one of the first operational clues to a fuel system problem. A failing MAF can cause your engine to hesitate when you accelerate rapidly, stall when you apply the gas or hiccup when you change the throttle position quickly.
Idle Thoughts
Another sign that your MAF is faulty is that your engine will run rough at idle or surge. The difference is a rough idle will cause vibration while sitting still and a surge will cause the engine RPMs to change noticeably without driver input.
Other Issues
A bad MAF may also be indicated by poor starting ability or excessive fuel use that will result in black smoke emitting from the exhaust on acceleration. A further indicator that is difficult to observe is an overly lean condition which will actually cause a slight increase in mileage but can be very harmful to the engine because it increases the temperature inside the cylinder and may lead to pre-ignition or spark knock.

 

Engine runs perfect until it splutters on occasion. Really seems more likely to be bad gas from storing/fill out of town where few would have bought premium over the winter, but with modern electronics nothing would surprise me. Thanks for the thoughts...and if treating the gas and driving it fixes it then the dealer will be very happy since they couldn't find fault with the MAF!

Bruce

 

I spoke with the shop foreman on Friday by phone to discuss the problem and he pointed out the fact that the car has two separate air intakes and two MAF sensors measuring air passing through them. If the two sensors register even a slightly different airflow the CEL will light, and MAF error code registered. If a mouse got in there over the winter and ate through, or plugged with a nest, one of the intakes that would cause a flow imbalance, and he thinks that is more likely the cause. The intakes are not user accessible so they'll have to pull it apart, something they didn't have time to do the day I took it in.

The good news is he says there's no urgency to bring it in as the engine will run safely on ECU mapped values. I may run it up a couple of ramps to look underneath anyways. I'll update when it gets all sorted out.

Bruce

 

I hope the mouse will be ok in the meantime!

 

If he was in there he'd have been sucked through the engine the first time I let it off the chain. Maybe that was the hestitaion I felt

 

I doubt it's plugged but anything is possible; probably one of the sensors is going bad.

 

What was the actual code you got?

 

I was never told the actual code.

 

There is still a log on the tool (if they used a IDS), that will be very helpfull to know.

 

I'll ask when I take it back in.

 

Mine is also at the shop for check engine. The code was P2096 (O2 sensor) but now that code is gone and a new code came up which is P0101 (MAF). My car runs and idles fine. Let me know what your dealer finds out. Thanks!

 

P2096 = Sub feedback too lean bank 1.

As I don't know how this works on x150 cars (ie difference from the normal fuel trim and what they call Sub feedback), I can't tell what it means. It seems it has something to do with the post O2 sensor (so downstream one). It would be interesting to actually see the fuel trims, are you able to read these yourself?

Maybe the P0101 is also related to the same issue.

Have you done anything to the filter system?

 

Thanks Avos for the info. They did replace post O2 sensor and the P2096 code is gone but there is now a new code P0101. I wonder if it's the Mina Air Induction kit with the conical filters? I remember Chris telling me a few weeks ago they discontinue the kit because customers were complaining check engine lights after install but again I've had this kit installed for a year now with no CEL until now.

 

The mileage you driven it in the past year may be more important than the time itself.

It may have just taken a few miles to show up...can you revert the intake or put a different aftermarket kit on it?

 

There could be a relation, as changing from a panel filter to a cone filter alters the airflow over the maf itself, and then it depends how far of the readings will be and how sensitive the checks are. With early cars there was certainly much more flexibility, the later ones seem more sensitive.

You could already get some idea how far of the readings are if you check the fuel trims.
Now as the P0101 is a rationality check, so the airflow should be within 25% margin of the expected airflow at a certain throttle angle.


Now assume for instance that the actual airflow is 15% off (gives more air than actually gets thru) at a certain power range due to the conical filters, you are still within most tolerances. You would see then negative fuel trims.


I know you have done some more tuning, then maybe if you also get 10% more airflow at a certain range, you are 25% off, and the code will be set.

Just a thought above of course, but again am very disappointed in Mina that they sell products they have not thoroughly tested. I would also ask them what sort of issues others have had to help in diagnosing; the least they owe you I guess.