Posted on Mar 27, 2011

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My '01 impala 3.4 v-6 flat spots when COLD, at around 20mph. the idle is ruff with random misfires. acceleration is overall poor. when HOT, most symptoms go away leaving only some slight acceleration resistance. full throttle acceleration will by pass the flat spotting of speed/rpm's wheather COLD or HOT. ALLREADY DONE is new plugs/wires, 02 sensors (2), maf sensor, 2 coil packs, crankcase speed sensor, fuel filter, fuel pump checks ok. we have a new ecm brain ready to program and try. The joker is:...my oem 3.4 went bad and this is a replacement '00 olds 3.4, with 64,000 mile (so it sat up for 5 to 6 years. Yes, it was serviced and fluids/filters changed on installation ( I checked it). But i suspect the installer of sabotage since he owed me the labor from a previous botched repair job and didn't want to do this install to begin with.............my current shop is frustrated.......help!!

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raj somaiya

Chevrolet Master 5,370 Answers
Posted on Mar 27, 2011

raj somaiya

Chevrolet Master

Joined: Nov 12, 2010

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Depending on mileage, but possible tune-up could fix it. if already done then check ignition coil pack and ignition wires also spark plugs, check vacuum hoses for leaks or porous, last injectors clogged - use some techron fuel injector cleaner (wal-mart has them). Also get the throttle body and iac valve cleaned by throttle cleaner . Also this other possibilities are to be checked and confirmed.:---- Engine running rough or misfiring can be cause by the following:

1.Defective spark plugs
2.Inadequate spark/coil, defective spark plug wire.
3. Lack of compression
4.False air leakage.
5. Faulty fuel injectors.
6. Insufficient fuel pressure.
7. Contaminated fuel.
8. EGR valve that is leaking.
9. Oxygen sensors.
10. Throttle position sensor.
11. Manifold absolute pressure sensor
12.Mass Airflow Sensor
13.Idle air control valve
--------- This should help.Keep updated.Thanks.Helpmech.

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Jag XKR 01 p0300-p0308 and P1316 codes. Doesn't pull when cold and idles roughly when hot. Acceleration otherwise seems fine and I haven't noticed a smoky exhaust. Changed the coils tried a used MAF

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2001 Impala

Jag XKR 01 p0300-p0308 and P1316 codes. Doesn't pull when cold and idles roughly when hot. Acceleration otherwise seems fine and I haven't noticed a smoky exhaust. Changed the coils tried a used MAF

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