2006 Volvo S60 2.5 AWD, Endless search of problem

[Unownreality]

About a month ago, my car starts stalling out on me at idle. Didn't matter if the car was cold, warm, hot, if I didn't keep revving the engine it would stall out on me. I have a pocket scanner and the codes read P0101 and P0170. The car had done this before, and I knew I had an issue with the MAF being dirty, so I grabbed my cleaner but this time it did not work.

The first thing I did was check for vacuum leaks. I checked every hose, ever joint, and did a smoke test, and no leaks at all. So I then began to look at the MAF and replaced that thinking it might be the issue. It wasn't the issue.

I then decided to take the car to the dealer and see what the problem is there, and then decide to either do the work myself or find a local mechanic. They said my PCV system was clogged and it would cost $1700 to repair. To hell with that, me and my buddy did it ourselves for $600. We used all Volvo parts or OEM, and we did solve the clog. We performed the glove test before and after as well as a smoke test after the fact. No leaks, good fuel pressure, and while we were in there changed all hoses and cleaned the fuel body. This time, the car went from running lean, to running very rich and developed this stuttering thing. At Idle, and only at idle, the car sputters and you get massive puffs of air out of the tailpipe. No real abnormal smell coming out of the car. No longer stalls at start or stopping.

Before my 30 day returns was up, I decided to trade in the MAF in case it was a defect, and that did nothing.

I looked at my car under a more advanced scanner, and saw a very low reading that did not fluctuate on the O2 sensor (upstream). Revving the car did not alter the value, so I knew I had a bad O2 sensor. Changed that out and while it runs far better driving, I still have the nasty sputter.

I'm kind of at the end of my rope here. I don't know what else the issue could be, and the dealer and every mechanic has not really been any help in telling me what the real problem is. Maybe someone else had the same issue?

Here it is again of what I have done thus far:
- MAF (2 new sensors)
- Cleaned Throttle Body
- Unclogged PCV system and leak checked
- New O2 sensor
- Fuel and oil pressure good

[mrbrian200]

With everything you've already done if P0101 (MAF) and P0170 (Fuel trim) still persists I'd look at the throttle body. When the Bosch type throttle bodies start to fail they have problems controlling the throttle plate in the range between idle and part throttle. The engine computer interprets this as too much or too little air and triggers the code for the MAF sensor. The fuel trim code is just fallout from the air fuel ratio being thrown off with too much or too little air entering.

[oragex]

I've also read about throttle body problems on 2006up (not the same thing as on 2001-2002)

May as well google a bit on FPS (if you have one) and PEM

[Unownreality]

when I had the throttle body out, I cleaned it and made sure it was in good working order before I changed the gasket and put back

[chrism]

When was the last time you installed new spark plugs?

[XC70Rider]

With it running rich you may a leaking fuel injector. How did the pintle caps and O-rings appear when you removed the fuel rail to clean the PCV system? A broken cap or pinched ring will cause a leak.

Read the thread I recently started regarding a P0101 and the narrowed down ECM-121B code:

viewtopic.php?f=9&t=87435

After cleaning the injectors I installed new O-rings, pintle caps, and filters.

[mrbrian200]

Leaky injector causes a different set of problems. You'll get the codes for fuel trim and sometimes misfire codes and/or long crank/hard starting because the engine has to clear a flood before it can start. But usually that doesn't set P0101 (MAF). Leaky injector by itself doesn't affect the amount of air entering through the MAF sensor.

Degraded injector o-ring seals would cause a lean condition. He's running rich. Something is restricting the amount of air coming into the engine. In my mind it's likely the throttle plate not opening (sticky internal mechanism). Sitting on my chair unable to run tests and look at the live data myself I could easily be wrong. That's just the direction I'm leaning.

Note to Unownreality: when the internal mechanism starts to degrade inside the throttle body problems aren't necessarily obvious in key on/engine off tests. Issues with the throttle plate not responding or moving properly show when watching live data while the engine is running/driving. Moving air across the throttle plate on a running engine seems to create tension or 'load' the mechanism and that's when you'll spot problems. On the bench or with the engine off if may appear to work perfect.

[XC70Rider]

If you read the later half of problems it went from running lean to now running rich. Also claims there are now no MAF related issues. Before I replaced the ripped O-rings and broken pintle caps it was hard to start, ran rich, and would shake like a diesel after shutting off. That only lasted 1 day until I refurbished the injectors.

[oragex]

By refurbished you mean cleaned them with an ultrasonic bath?

[Unownreality]

To answer a few of the posts.

- New plugs, and coils this past summer. Did the whole tune up of the car
- The injectors, you may be onto something here. When i removed the fuel rail, all of the caps where deteriorated, and I couldn't find replacement caps. So the only thing in them right now is the o-rings that were replaced. I can't seem to find just the plastic washer caps. Napa and Autozone had no idea, and just tried pushing new injectors at $80x5. Figured as long as the o-rings sealed, should be good.
- I cleaned the MAF with a cleaner, and wire brush. Tested using the computer, and the throttle opens and closes as necessary.

Also, after resetting the computer post O2 change, no more P0101. Now just the P0170 code.