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Toyota Repair/2000 celica gt code p0171

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QUESTION: I have a 2000 celica gt 125xxx miles with a po171 code that is giving me a fit. Already replaced;
spark plugs (originals, heavy oil deposits)
thermostat (stuck open)
pcv valve (chattering)
intake gasket (changed LTFT from +26 down to +19.5)
MAF (cured hesitation no change to LTFT)
both O2 sensors (previous mechanic)
fuel pressure 48psi at idle ,no exhaust leaks between engine and sensor, have pinched off all vac lines on intake, no change in STFT when I spray around intake. At idle the LTFT is +19.5, total trim 1.31, iac 30%. This car starts quickly with that Toyota pop ,idles correctly and drives strong. I just can not get the fuel trim down in the good range. Any help would be appreciated, I've run out of tricks on this one. Thanks Bob

ANSWER: Hello, have you taken an actual intake manifold vacuum reading, if not please do that and let me know the reading you are getting at idle.

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QUESTION: Hello again intake vacuum reading is 15-17 during high idle settling at 17.5 hg" @750 rpm with a steady needle. Have since benched intake, new TB gaskets, clean and lube IAC. Idle quality improved some but now have a slight tip in hesitation. LTFT is now +18 at idle as well as under load, 0 +/-6 during part throttle/ no load cruising.(short test drive)Thanks

ANSWER: Thanks for the reply, when you get a chance check engine compression and let me know the readings.

---------- FOLLOW-UP ----------

QUESTION: Happy 4th to you. Compression readings cold dry 160 170 170 160 wet 195 all Thanks

Answer
Nothing wrong there, I think you may have to replace the ECM, before doing so check all the computer connections for corrosion or bad connections, I think the computer is under the hood on this one near the front, although they are pretty much sealed in a box there is always a possibility of moisture getting in.

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