Hi, I have a 1999 Pontiac Grand Prix GT (3.8L L36 Motor - Normally Aspirated). After the car not running for 4 weeks - would stall aout after warm up with no Codes display) I fianlly deducted that it was the MAF Sensor. I replaced the MAF 4 Days ago and finally took it on a So Cal Freeway in bumper to bumper traffic. Ran great, but then received the Code P0171 - Lean Bank1 and it has trouble accelerating and actually does appear that one bank is lean, becasue my exhaust on one side has white smoke. Grrrr.
How can I fix Code P0171 - Left Bank Running too Lean on 1999 Pontiac Grand Prix
by JOhnZinOC in Huntington Beach, CA on April 13, 2010
4 answers 1 comment
ANSWER by gearhead10 , January 13, 2011
your exhaust system joins to one pipe on the rear of the engine and only separates into duel exhaust after the catalytic converter, so smoke on one side is not really an indicator that a certain bank has a problem. white smoke usually indicates some kind of fluid entering the engine through the intake system. these engines are notorious for developing engine coolant leaks in the intake manifold. The EGR valve directs exhaust gases through the lower intake manifold then through what is called a stove pipe through the upper intake manifold (which is made of a thermo plastic) to the intake air stream. This "Stove Pipe" gets very hot and will eventully melt the upper intake manifold which has coolant flowing around the stove pipe. I had this problem. got the lean code, with no real problems, then pow, white smoke and very soon an engine which will not run. The repair, if this is your problem is pretty easy with minimal engine knowledge, and a good repair manual. and NAPA has a great upper manifold with revised stove pipe. the problem is trying to see if coolant is in the intake manifold behind the throttle body and some disassembly is requirid to confirm if this is your problem.
COMMENT by Visitor , December 04, 2012
so what did you actually do did you change the gaskets im lost n need this done asap
ANSWER by chris l simms , April 14, 2010
check your 02 sensors
ANSWER by Visitor , January 07, 2011
I have the same car, same year and engine and experienced the same failure of the MAF sensor...got the P0171 code after replacement. I've changed the upstream o2 sensor and it had no effect...still searching.
ANSWER by Rickstine , March 04, 2016
Check your middle coil it might have a crack in it! I had the same problem ,found a crack in middle coil!