Yesterday I made the long drive back to school after a weekend with my buddy back home in Houston (450 miles). I swear as soon as I pull off the freeway onto the main city street, my car starts stumbling really bad and it has no power to it. Idle is terrible as the car is shaking pretty bad. There is also quite a bit of raw fuel spitting out of my tailpipes. Seems like the car is running on 4 cylenders but there is no SES light.

Today I bought a coil to plug in to see if that is the problem and of course it isn't. Would a bad ICM be to blame? It seems to get worse and worse as it gets hotter. If it ends up being the opti, I'm almost screwed. I don't have a lot of tools here at school but luckily my buddy has some and he swapped his opti this summer. I'm assuming there isn't any way for me to test it to see if it is the opti? Tomorrow I am going to take the coil and ICM to Autozone to test that out. I also just went outside and started my car up and checked for any arching with it being night out. There was none.

 

does it backfire? mine did and it was the opti, i have a friend thats a mechanic that has this small tool that lights up and blinks fast when you touch the spark plug wires when the flow is good and barely blinks when there isnt like any, and all of them worked good but 2 were slightly slower on idle, then when you press down the accelration( throttle body) then those 2 didnt work and it was almost obvious that it was the opti. i did the job twice cause i did it with a friend the first time, and it didnt start up and we thought we put it on wrong, and we checked the wires if its the right one on but its hard with the otvc,and then i did it agian the second time and it wasnt as bad cause you know how to take it apart better and then it didnt start up when it was done agian... and i used a voltmeter to make sure he did the spark plug wires good and i found out thats where he messed up lol, im 16 1/2 and i did it, it should be possible for you to do it, u also need a harmonic balancer puller and a new waterpump gasket.

 

It does pop pretty loudly when I was driving it. The raw fuel coming from the exhaust is pretty strong so I know at least one but probably more are not firing.

 

does it smell like gas out of the exhaust? and does it suck up more than usual?

 

i have always been told that the opti is either fine or toast. Meaning your car runs or your car doesnt. Not really sure but, just and idea. def. get your ICM checked

 

can someone tell me what an icm is, how much it is and what does it do?
thanks

 

Ignition Control Module, it does just that. I believe I paid 77.95 for mine at O'Reilly's, Also it could be the coil. I believe those are around...the 20's if I remember right, and the last time my Opti went out, the screws had backed outta the rotor and it was sorta flopping around in there lol, but the car still ran

 

how can you tell if either the coil or icm is bad?

p.s. which do you think is the best on this site:
http://www.thunderracing.com/catalog...vid=4&pcid=103

 

You can do what I'm doing tomorrow, which is take it to Autozone and they should be able to test it there.

 

I put in a new ICM and that definitly was not it. Seems the only last thing could be the opti and it seems like everything is on backorder. My options are:

1. GM Opti
2. Remanufactured Opti from Autozone (lifetime warranty)

What should I do?

 

Well I changed out my opti today and now its running great! Only problem is I ended up with one extra bolt lol. This was not nearly as hard as most people make it out to be and nowhere near as difficult as my headers!

 

my cars running exactly as you described in your orinignal post .. i hope its my problem too

 

Well good luck to you. I'm pretty sure it is, but you never know.

 

http://shbox.com/1/4th_gen_tech2.html#opti_test

http://shbox.com/1/coil_testing.jpg

An ICM either works or it doesn't. I don't think I've ever heard of an ICM causing an engine to stumble or sputter.

 

Damn, sounds like my problem too, runs fine for about half an hour til it gets really warmed up, then backfiring, missing, shaking, can barely get it up to speed. Let it sit for a while then it's fine again for a while. Did you use the Autozone one, or GM one, I am probably gonna buy the autozone one this week too.

Later