Posted: Sun Oct 14, 2012 4:38 pm Post subject: Rough idle - Innovate OT-2 scan pics. P0300 code
About a week ago my car started having a rough idle. No CEL, RPM's fluctuate 100 +/-. It isnt a constant rough idle, every 10-15 seconds the engine will shake a little and there is a noticeable change in exhaust sound along with vibration inside the car.
I have checked all plug wires and spark plugs, cleaned the MAF and IAT, checked for resistance on all coils, cleaned the TB, checked all vac lines for cracks/leaks. It has a brand new air filter in it so I know thats not clogged. Here are a few screenshots from Logworks for the OT-2.
Held at 1500~ RPMS
And a small graph from idle up to 1500 RPMs and then letting off the gas
The graph lines are small so from the top:
Blue: Short fuel trim 12
Purple: Spark advance
These two overlap
Black: Short fuel trim 1
Light Green: Short fuel trim 11
Orange: Long fuel trim 1
Dark green: Throttle position
These two overlap, right at bottom of graph
Red: Short fuel trim 3
Turquoise: Long fuel trim 3
Any help is appreciated
Last edited by VTSS on Fri Oct 19, 2012 11:45 pm; edited 1 time in total
Joined: Mar 21, 2009 Posts: 204 Posts per day: 0.07
Posted: Mon Oct 15, 2012 6:47 am Post subject:
A couple of things are noticeable, Your TP is not correct it should not be 0 at idle and 3 at 15/1700 rpm. your also showing something else incorrect ... the ECT shows that you are still in open loop, is your car actually reaching 186-188 * for the computer into closed loop or is your thermostat stuck in open position.
A couple of things are noticeable, Your TP is not correct it should not be 0 at idle and 3 at 15/1700 rpm.
The TPS looks good to me. The throttle plate stays closed on these cars at idle, adjustments are made through the IAC.
the ECT shows that you are still in open loop, is your car actually reaching 186-188 * for the computer into closed loop or is your thermostat stuck in open position.
Scans are more helpful in closed loop, so try and get a closed loop scan. Also, long term trim bank 1 and short term bank 1 are the only two trims that have a direct effect on fueling so all the other trims you are monitoring can be omitted from the scan.
Do you still have the bank 2 O2 installed? do you have the cat efficiency code disabled in your tune?
Thanks for the responses. All o2 sensors all still in place and I am still using the stock PCM/non tuned. I will scan again after I have driven it a little so the temps are up, that scan was after idling a few minutes on a cold start, 40*~. The thermostat is a 180* I put in last June.
Edit: Here are a few screenshots at operating temps
I checked all the plugs again, #3 was carbon fouled so I cleaned it - the rest were normal. What would cause one cylinder to carbon foul a plug? I also replaced the plug wires with AC Delco and reset the fuel trims. The problem is still there...
Edit: I checked the resistance on the injectors. 13~ for all of them except for cylinder #3, 6.5~. I replaced that injector, the problem seems to be gone (knock on wood) I havent driven it yet but I let it idle for 5 minutes.
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