obdII p0171, 1996 volvo 850 Non turbo

[izcali]

Hello, I have been working on my 96 volvo 850 for days without any success. I keep getting code: P0171 running lean.
problem: P0171---- unstable idle---------The vehicle runs ok while driving but when I get to an intersection, the car sitting there at idle, the engines begins to idle up and down and then gets ok, and the check engine light is on.
I have done the trying to fix the problem:
Replaced the front O2 sensor.
Cleaned the throttle system really good using a toohbrush.
Checked the distributor.
Replaced all the spark plugs.
Check the fuel pressure with a reading of 44 PSI.
Checked for any vaccum leaks spraying propane gas around all the hoses and found no leaks.
Replaced MAF sensor and a few hoses around there including the trap valve.
Using Premium gas 93.
Cleaned the Idle Air Control valve and the two hoses that go in and out of it.
Checked the vacuum hoses as well as the vacuum tree. Even the hoses under the thermostat on the intake manifold, and the one going to the fuel pressure regulator.

THE CHECK ENGINE LIGHT KEEPS COMING ON AND THE IDLE IS STILL UNSTABLE.

ANY SUGGESTIONS PLEASE!!!!!!!!!!!!

[MadeInJapan]

I guess what you have left then is making sure your fuel filter is clean and then that you have enough fuel pressure. Other than that, the MAF could be bad to begin with or the 02 sensor. Did you replace with OEM parts?

[izcali]

I have replaced the fuel filter, and the MAF was an after market unit. But Would I be getting a different codes if in fact the MAF was going bad:
P0100 Mass or Volume Air Flow Circuit Malfunction
P0101 Mass or Volume Air Flow Circuit Range/Performance Problem
P0102 Mass or Volume Air Flow Circuit Low Input
P0103 Mass or Volume Air Flow Circuit High Input
P0104 Mass or Volume Air Flow Circuit Intermittent

The code I am getting is p0171 and none of thew above.


thanks

[Ozark Lee]

The AMM/MAF codes can be deceptive and they will show up as O2 sensor range errors if the MAF doesn't quit altogether. It is a "goesinta" vs. "goesouta" thing. Many a time a MAF problem will throw an O2 sensor range error since it is trying to use the MAF as its benchmark to measure from.

If you still have your old MAF around try to clean it and put it back on. Use electrical contact or MAF cleaner on it. Just spray it and let it dry. Don't scrub it or even touch it.

...Lee

[MadeInJapan]

Another thought...if it is the MAF then just unplugging it and clearing the code and then starting your car will give you other trouble codes but not the one you were getting.