xeroid Posted May 24, 2013 Report Share Posted May 24, 2013 Stock 2004 Impala LS 3.8 Trying to solve a P0171 condition! Here are some OBD readings. Can anyone interpret these and or sees any problem? Measurements taken while idling in the driveway: Short Term Fuel Trim 5.47% - 7.81% Long Term Fuel Trim 16.41% Bank 1 Sensor 1 Oxygen Sensor .030 - .780V Bank 1 Sensor 2 Oxygen Sensor .23V Mass Air Flow 3.27 g/s 0.4 lb/min Intake Manifold Pressure 31 KPaA 45 PsiA Done Already: New Exhaust New Fuel Filter New MAF Sensor NEW PVC Valve Quote Link to comment Share on other sites More sharing options...
AL Posted May 27, 2013 Report Share Posted May 27, 2013 Its adding fuel which means you probably have a vacuum leak somewhere Quote Link to comment Share on other sites More sharing options...
Imp558 Posted September 17, 2013 Report Share Posted September 17, 2013 Okay, I got a P0171 tonight! This is my new (80K mile) L67 with a 4T65-E HD that I just put in. When I was driving it seemed like it was running out of gas right of the line and bumping over and over. Then it popped the P0171, (System too lean) to support my theory. Tomorrow I'll try a MAF but I can't see it being a vacuum leak because for 1 it's a boosted engine, and 2 I just tore it down and did all new gaskets from the intake up and redid all the vacuum lines when I did the swap. I was thinking fuel pump but it's only done this periodically, like 4 times now in all the trips to and from the paint shop and stuff. Quote Link to comment Share on other sites More sharing options...
chevelle3504speed Posted September 21, 2013 Report Share Posted September 21, 2013 I put an L36 in my '95 Cutlass Supreme and ended up putting a fuel pump in it. It ran fine most of the time, but would bump and surge occasionally at idle, especially at start up, and just lacked power at 3/4 + throttle. It didn't necessarily run badly, just felt weak. I put a fuel pressure gauge on it and saw that it only had a max of 35 psi of fuel pressure with the L36 installed. When it would start surging, the fuel pressure would drop down to 20 or so, and it would level out when the fuel pressure got back up to about 30. The 3100 fuel pump was too weak for the 3800. I would suggest putting a fuel pressure gauge on the fuel rail to see what kind of fuel pressure you've got. Quote Link to comment Share on other sites More sharing options...
Imp558 Posted September 22, 2013 Report Share Posted September 22, 2013 I tried that the other day and my fuel pressure gauge didn't work, it figures. Right now I'm leaning towards mass air flow sensor. I ruled out everything that could cause a vacuum leak and now when I unplug the mass airflow sensor it runs great but in limp mode. Quote Link to comment Share on other sites More sharing options...
Imp558 Posted September 22, 2013 Report Share Posted September 22, 2013 Yup, mine was a MAF, swapped the one from the Lesabre in and it's fine. There's a $100 date. Quote Link to comment Share on other sites More sharing options...
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