BlackBird87

iTrader: (6)

Car starts and idles fine, once you drive it for about 10 mins it starts to stumble and randomly misfire once the revs go about 1500k. I let it cool down for a bit and it drives fine but soon starts up with the same ole ****. Sounds heat related so i picked up another icm and spaced it off the head and took it out today, drove it for about 30 mins and stopped at the mall. Got back in and get on the highway and it starts stubbling again. im at a loss the opti is a year old and sealed up tight but the coil is unknown

SS RRR

iTrader: (2)

Fuel pump is a possibility too.

whytryz28

iTrader: (28)

Test the coil and fuel pressure/regulator.

BlackBird87

iTrader: (6)

How do you test the coil, regulator is brand new but ill look into the pump

Jr.Samples

Not good. I am replacing the ICM and spacing the coil today. I have the EXACT same problem and was hoping this would fix it. Michr go ahead and pick up a new coil for giggles while I am at it. This sucks!

BlackBird87

iTrader: (6)

The worst part is you dont know if its fixed untill youve driven it away from the house. Let me know how it turns out

95mysticta

iTrader: (4)

Has it tripped any codes?

Go to www.shbox.com for the voltage readings you do on the coil, icm, and opti harness to see where you stand and where the problem resides. Do no just throw parts at it hoping to fix it.

BlackBird87

iTrader: (6)

It threw a code once and it was an icm code. 41 or 42 i cant remember. It hasnt thrown a code any other time its been doing this tho

VinR1

iTrader: (17)

Could also be the coolant temp sensor in the water pump. I forget the technical terms but if it doesnt give the computer the correct temp, car is sluggish and runs rough...

BlackBird87

iTrader: (6)

temp sensor is fine

Jr.Samples

I pulled of the coil and ICM, The coil output connector to the opti looked a little pitted/cooroded. I went ahead and found a Delco on ebay and ordered it.

I have a new ICM I am putting on so I hope this is going to fix this.

I have a feeling not. I do throw the random misfire code once in a while when it is running rough.

BlackBird87

iTrader: (6)

I wont get missfire codes since im obdI but im gonna take everything off double check the grounding points and go for a ride and test the coil if it starts acting up. I did hook up my wideband today and take it out and when it was started missing it leaned out like around 17.1 then back the normal then spike to lean again

95mysticta

iTrader: (4)

Dude did you read what i just posted. Why are you throwing money and parts at it if you dont know what the problem is??? Do the voltage tests and see what is actually bad! Very simple to do and your no stressing yourself and wasting time and money on parts that may not be the problem!

Jr.Samples

For me I do not know the history of the parts and feel better changing them out to prevent problems down the road. My car has 160K and these parts looked original.

Thanks for all your help!

95mysticta

iTrader: (4)

To be honest and alot of folks on here agree to the comment "if it works dont touch it" when dealing with lt1s. Sometimes aftermarket coils, icms, etc can make it worse as there **** quality. Do the simple voltage tests to find the problem is and stop beating around the bush its very simple and will tell you wtf is actually going on. Maybe im just retarded for trying to help solve your problem cause you dont seem to be listening.

Jr.Samples

Don't take it personal. Everyone appreciates your help. I simply explained why I go ahead and like to change parts as I go.

BlackBird87

iTrader: (6)

Im going to be testing everything later on today, but if everything is fine on first start up and during idle wont everything read on to be fine. i understand if i had a no start. And im not just throwing money at my car i had an icm code so i picked up a gm icm from a trusted local member for next to nothing and everything was fine for the first 30 mins of driving. How hot do these icms get cuz i mine is blazing hot i have to let it cool down before i can handle it. Lastly i posted my afr's during the strumlbing is it going crazy lean due to lack of fuel or because the oxygen isnt being used for combustion?

ZFreie

Any clue what the o2 sensors are doing during the stumbling? Do you have a way to datalog the car?

Honestly, having a laptop and buying the aldl cable is the way to go. Scanning the car takes 3 seconds and no more guessing at what COULD be wrong, its usually very obvious.

.02

Sounds closed loop related based off that.

95mysticta

iTrader: (4)

Do the voltage checks to verify everything is fine cold. Once it acts up do it again. Those harness's are very easy to get to. Im thinking more if its not icm heatsoak that its your fuel pump on its way out or the relay is going bad. Buddy of mine had the same issue when it got hot it would do the same. Turned out his fuel pump relay was getting hot and causing it to go lean and want to stumble and barely run then die.

BlackBird87

iTrader: (6)

ya i have everything to log it but i dont really know what to look for. the o2's are brand new and the voltage moves from like .2 to .8 like its suppose to. The car did this before then the old o2's were bad and it never went into closed loop.