P0171

[tloukaitis]

'95 Riviera periodically/intermittently throws a P0171 Code. Sometimes several hundred miles without throwing it; sometimes 2 times in 10 miles. Have checked for vacuum leaks & bad electrical/ground connections to no avail. Sometimes accompanied by a P1257 code (this code only happens when car is not entirely warmed up, within the 1st 5 minutes of driving). Any ideas? Thanks.

[John Csordas]

P1257 is boost control solenoid problem. Causes car to run rich which could be related to P0171 . Which code comes first if you clear it?

[tloukaitis]

If both, usually P1257. But, P0171 comes by itself about half the time. P0171 signals a lean condition, not rich.

[John Csordas]

You may have to use a smoke machine to make sure you don't have any vacuum leaks. A lazy oxygen sensor or a MAF sensor could also give you lean code. Oxygen sensor is cheap so if it is original that is any easy way to go. Get a good quality sensor though. Do you have access to scan data when the problem occurs?

[tloukaitis]

Problem is intermittent, so cannot see scanner at right time. I've used starting fluid, no vacuum leaks identified. Replaced both MAF Sensor & Oxygen Sensor several months ago due to codes thrown; now no codes for those.

[John Csordas]

I have seen many problems with MAF sensors

[tloukaitis]

Unplugged the MAF today; erratic high idle & MAF code returns. Plugged it back in, no MAF code (after reset) & runs good.

[tloukaitis]

Could the PROM be bad? I have a PROM from a non-supercharged car available. Would changing that out be a good test, or would that really screw things up?

[John Csordas]

I don't think the prom is the problem. You have to see the data from a scan tool to diagnois any further at this point