Check Engine Light and Codes p0171 p0174
Thread Starter
Burning Brakes
Joined: Mar 2004
Posts: 842
Likes: 4
From: Corpus Christi TX
St. Jude Donor '05
Check Engine Light and Codes p0171 p0174
I have tried search and I have found several posts that reference aftermarket intakes. I am bone stock.. down to a stock air filter. The codes show lean fuel in both cylinder banks. I have new plugs, new wires, new filter, and a new PCV valve and codes keep returning. I also have some idling irregularities (rough idle) at times. Car runs strong otherwise.
Any ideas as to what could be the cause? Bad MAF sensor? I hate to chase it down by throwing parts at it... but I am at a loss. Any help would be much appreciated!
Any ideas as to what could be the cause? Bad MAF sensor? I hate to chase it down by throwing parts at it... but I am at a loss. Any help would be much appreciated!
Drifting
Joined: Feb 2007
Posts: 1,793
Likes: 7
From: Santa Maria Ca.
It was the MAF sensor on mine-chased those codes for weeks,looking for vacuum leaks,checking 02 sensors,etc.
As soon as the engine went into"closed loop",I'd get the codes-sometimes one,sometimes the other,sometimes both.
Sort of narrowed it down by accident-rechecked all the connections on the intake for about the 4th time(Vortex Rammer),and took it for a spin-NO CODES!,but when I pulled it back into the garage,I looked over at the bench and noticed I'd forgot to put the air filter back on-SO,I put the filter on,and within 15 seconds,both codes were back...pulled it off again,reset codes,no codes(it did idle really rough without the filter on,also)put the filter back on,instant codes.
SO,I tried it again without the filter-no codes,but rough idle-Unplugged the wires from the MAF while it was barely idling,and the idle smoothed right out(also got a MAF code,but no lean codes till I plugged the MAF back in and reinstalled the filter)
Not very scientific,but it was enough to tell me that the MAF sensor was at least PART of the problem,since it actually ran better with it unplugged.
Went down to O'Reilly and picked up a new(not rebuilt) Cardone MAF,and it was a POS-the car had a massive dead spot between 750-1000 rpms,so took that hunk of crap back and got a rebuilt ACDelco unit,and all is as it should be-no codes,and the car runs like new! That was about 3 months ago,and I haven't seen a lean code since.
As soon as the engine went into"closed loop",I'd get the codes-sometimes one,sometimes the other,sometimes both.
Sort of narrowed it down by accident-rechecked all the connections on the intake for about the 4th time(Vortex Rammer),and took it for a spin-NO CODES!,but when I pulled it back into the garage,I looked over at the bench and noticed I'd forgot to put the air filter back on-SO,I put the filter on,and within 15 seconds,both codes were back...pulled it off again,reset codes,no codes(it did idle really rough without the filter on,also)put the filter back on,instant codes.
SO,I tried it again without the filter-no codes,but rough idle-Unplugged the wires from the MAF while it was barely idling,and the idle smoothed right out(also got a MAF code,but no lean codes till I plugged the MAF back in and reinstalled the filter)
Not very scientific,but it was enough to tell me that the MAF sensor was at least PART of the problem,since it actually ran better with it unplugged.
Went down to O'Reilly and picked up a new(not rebuilt) Cardone MAF,and it was a POS-the car had a massive dead spot between 750-1000 rpms,so took that hunk of crap back and got a rebuilt ACDelco unit,and all is as it should be-no codes,and the car runs like new! That was about 3 months ago,and I haven't seen a lean code since.
Tech Contributor
Joined: Dec 2006
Posts: 10,962
Likes: 29
From: Van Buren Arkansas
Wounded Warrior Escort '11
Check that airbridge and see if its possibly off on the bottom of the intake. If you had the intake off for any reason, check the small black plastic line on the back of it.
