Code P0171

MATTHEW KLEIN

MEMBER
1996 BUICK PARK AVENUE
150,000 MILES

After about thirty minutes of idling or driving starts misfiring, stalls, sometimes it does not want to start but does (acts like battery is dead but not). Other times it tries to turn over. I replaced the ignition control module, coils, plugs and wires, due to a multiple misfire code p0131, I believe. That seemed to work light gone. Drove fine for two weeks, now all this again. This time I was letting the car warm up and ten minutes later it was stalled when I went to get in it. The code reads p0171 lean bank 1. I drove it fine yesterday today I let it idle for twenty minutes the put it in drive and misfiring started, engine light flashing. I restarted it drove fine two mile to buddy's garage to read codes. P0171, I am lost I do not know where I should start. Any suggestions please? I am thinking clean MAF, but from there I do not know. I am assuming I need my fuel pressure read, and vacuum pressure read. I am just wondering if it was that bad why twenty minutes it is fine.

1 Reply

JIS001

MECHANIC
3,408 POSTS

Check fuel trims on both banks. If both are lean at idle, check for a vacuum leak and check for low fuel pressure. If pressure okay then you could have bad injectors. At idle also look at your mass air flow sensor reading. Have the scan tool set for grams per second. Reading should be close to the engine size when engine warmed and all accessories turned off. So if you have a 3.8L engine, you should in theory read 3.8g/s on mass air flow reading but a reading from 3- 4.5g/s should be about normal assuming this were a 3.8L engine.

Next while having someone driving and you looking at that reading. Pick up speeds up to forty mph and keep steady. Have the driver floor it quickly. The mass air flow should respond pretty fast and read over 100g/s. If it does not respond quickly then replace with the original A/C Delco if possible. Some other brands cause more headaches then what you started. Let us know what you find.