acts wierd after warm

[josephg15]

so i got my car running after it felt like it was hesitating...the cars runs great for the first 5-10 minutes...i took it on a test drive and it ran great, brought it home and let it idle for like 3minutes, then the idle started jumping from 400-900 rpm, and the car sounds rough like a misfire...any ideas. could it be the IACV, but why does it only do it after 15 minutes...thanks

[sr power]

prolly your o2 sensor. if your car is obd I it can take a long *** time for the o2 sensor to heat up. and until it comes to temp you run on preset values with the sensor out of the equation.

[dcmxsa]

i think im in the same boat as you josephg15...i havent got a clear answer tho.

[S13FASTBACKSR]

yes your o2 sensor takes time to start working, the engine has to be warm...check for voltage at the ecu for your o2 sensor and by the way are you running rich at all? other things to check for when you have bad idle and misfire is your timing, spark plug gap, maf which would also cause you to run rich..check your fuel filter to see if it is clogged, one of your fuel injectors may be getting stuck after 5-10 minutes or so..also check your ecu it sounds like it could be a possible ecu problem..if you turn your key on you will see a l.e.d. on the back of your ecu come on..now start your engine..if it goes off you have a good ecu if it stays on your ecu is bad

[Gramentz]

Have you checked to see if you're throwing any codes??

[josephg15]

ok when i get home i will see if the ecu light stays on, i have a stock sr20det with a 255 walbro fuel pump, and just changed the fuel filter, when the car started having the idle problem (idle jumping up and down) i unplugged the 02 sensor and nothing happened.

[S13FASTBACKSR]

ya check your ecu and check for voltage for your 02 sensor still