mattcossel29

iTrader: (2)

I have been having a problem with my car that I have been trying to track down since I have gotten it running. Once warm the car wants to miss or stumble at low rpms with none to light throttle. I can tap the throttle and it will come alive until a few seconds later. It seems line one cylinder goes down and the idle changes and it does this until I tap the throttle but only does it when its warm. At WOT she runs like a champ and does not miss a beat.

Recent parts I have replaced:
- Optispark
- Coil
- plug wires

I was possibly thinking it being the ICM.. Any thoughts or opinions would be much appreciated. Thanks!

WhyHelloOfficer

iTrader: (5)

The fact that it runs well at WOT and cold startup points to the problem being in your closed loop operation. I would unplug your MAF Sensor once the car gets up to temperature and see how it runs. When the MAF is unplugged, it will send the car back into open loop operation/safe mode.

Another easy alternative would be to swap your MAF sensor with a known working car. Same with the O2 sensor. I believe your symptoms of poor closed loop driveability are caused by one or both of those being bad.

mattcossel29

iTrader: (2)

I went out and unplugged the MAF and it is still doing it. I will hook it up to the laptop tomorrow and see what Tunerpro has for readings on the o2 sensors.

Thanks!

Enforcerws6

iTrader: (1)

I was having a similar problem and it was a bad O2 sensor but I had a SES light on as well

white ghost

iTrader: (1)

Maybe im confused, but wouldn't it be exactly the opposite? Wot and idle are both closed loop operations? And off idle and part throttle (<60%) are open loop operations. Kinda makes me think it could be in the tune if its not your plugs/wires. Though if it idles differently it could be Timing.

ZFreie

I also had a bad o2 and at first did not throw a code, it didn't throw a code till it got much worse then forced its self into open loop.

You have them backwards, open loop is when the pcm uses a set # of figures and ignores more of the sensors(cold start up and WOT). Closed loop is when it take into account things like the o2s(drive-ability).

white ghost

iTrader: (1)

You are correct sir. I knew what they did but I had the titles backwards. ( I was always told. That open loop was "open" for input from the sensors.)