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Hi all,
Ive searched the forums and found some good info on the P0171 code. Heres a little background into my issue. I have been having issues with rough starts for approx 2-3 months now. Just this last week the car threw the P0171 code after I filled up with gas. I have put the car on the scanner and my STFT/LTFT readings are in the 10-16% ranges. The car itself is having no real driveability issues, no hesitation, although it does feel like it is surging a bit at startup. I cleaned the MAF two nights ago and the code went away for approx 6 starts. It is now back on, and I am still getting the same readings. Any ideas would be helpful. Thanks!

The two usual suspects would be poor battery connection (or loose) and misrouted or broken vacuum lines.

Although the FSM diagnostic hints suggest the MAF and your description about cleaning with some success appears to point you down that road. You should try to get it scanned if possible to see if the maf is falling into the normal area of operation.

for what its worth, the MAF is reading 10.115lb constant with no fluctuation

Give the wiring a good check over to ensure it's not back and then, it sure looks like the sensor is bad.

azmedic85308 wrote:for what its worth, the MAF is reading 10.115lb constant with no fluctuation

Isn't the MAF supposed to fluctuate with the amount of air going in? If so, then your MAF is bad.

not sure if its my scanner or not, but its still giving me the same reading with the wires unplugged.

May be a totally dead sensor. You are testing this with the car running and not running correct?

yes, testing this with the car running. no reading changes with higher rpms or at idle.

That ain't right. You should begin looking for a parts/car yard to get another MAF.

just checked the voltage on the wire harness, its reading between 13-14vdc

tried a different MAF this morning, still no changes. Still throwing the DTC.

Do another scan at idle & again at 2000 rpm. Get LTFT, STFT & MAF frequency.

2000RPM
STFT 3.6%- -0.7%
LTFT 14-16.8%
MAP 8.6in.hg
MAF 10.115lb/min

IDLE
STFT 14.8%-16%
LTFT 16.3%
MAP 10.6in.hg
MAF 10.115lb/min

I was hoping for the reading for MAF frequency. It should be around 2,000 hz (mhz?) at idle & go up around 7,000 at WOT. I don't know what the normal reading is when checking lb/min.

let me dig a little deeper and see what i can find.

ok so the MAF frequency is running about 1270hz and6800hz

Everything seems to be pointing toward a vacuum leak. Have you checked for leaks yet?

ran into something interesting while checking for vac leaks...checked the vac hose coming off the FPR and it has a slight fuel smell. I ran my fingers on the male end of the FPR and felt a little gasoline on my finger. Related by chance? Or another problem I need to diagnose/repair?

Please get that repaired ASAP by replacing the fuel pressure regulator. Worst case scenario is a backfire that causes the intake to explode and an engine fire. It has happened to others. Once it's replaced, scan things again and see if things have improved.

Ive got the FPR here, how do I remove the old one and replace it. Also to depressurize the fuel system I just pull the FP relay and start the car til it dies?