Hi Everyone,
I have a 2001 Volvo V40 which runs just fine as long as I accelerate slowly. Punching the accelerator causing the engine to starve and run rough. I have cleaned the MAF with the correct spray and that did not help.

The next morning after cleaning the MAF and a short ride, I parked the car for 1 hour and when I came back, I had a check engine light on, P0130 is the code I retrieved.

I have heard that this code can be caused by many things, not only the oxygen sensor, including a vacuum problem (which some posters say can cause a lean mixture). Since the car does not run rough just idling or below 3000 rpm or so, I would suspect vacuum, sensors, fuel starvation.

I have replaced the fuel filter (that was my first thought) and that did not help.

Any thoughts anyone?

 

The mechanic made it clear that the valve only begins to float at around 5000 rpm and that is what caused the misfire and subsequent CEL. Driving less aggressively below 5000 rpm will be ok and the "bad valve" will not be a problem unless it begins to float.

No, he did not remove the valve cover and watch the valve to witness the float, furthermore his attitude that this would not be a problem as long as I kept the rpm below 5000. I asked can he simply replace the bad spring or other hardware to stop the floating?
No, he said that the ONLY solution is a complete valve job $4000-5000, yea right, although he doesn't want to do it because most likely there will be other problems with this ML320 since they have a history of problems. I wish I knew that before I bought it but I thought that Mercedes made good cars and like I said I really like this car (when it isn't having problems).

I guess I am doubting this mechanic after all, I am beginning to think he is good for some things but diagnosing ML320 codes are not his thing. I also feel he knows that he cannot discover the real problem so this is his way of sending me off on my own, just don't drive to aggressively!

My questions are is a floating valve the only cause of a misfire at high rpm, even I know that there could be other causes. Plus when this condition occurs the CEL comes on immediately, like press the gas and light is on. I don't even notice the engine doing anything but the CEL comes on immediately and the transmission doesn't shift correctly and the engine runs rough until I turn it off, then everything back to normal.

Is it true that a bad MAF would cause multiple misfires on different cylinders or could it be just one.

I guess I need to take it to the dealer who I really don't trust, the service advisor at my local MB dealer actually implied that if have have to ask how much I really shouldn't own a MB!

It's a nice car, handles well, quiet and small V6 gets decent gas mileage, what to do?