full bolt ons, thunder racing 230/236-112lsa. the car ran like ****, i change plugs, wires, lots of sensors, radiator,t-stat, header gaskets, put stock balancer back on no more underdrive. the car ran very good after all that, it didnt break up or rpms hang up anymore. after about am hour of driving rhe problems came back but not as bad. any info? its got pcm4less tuned for the cam

 

Explain "ran like ****." You need to be more detailed. Is it when the car is warmed up? All the time? Certain RPMs? More info please.

Perhaps your ICM is bad. Once they get hot, they tend to fail, as do most electrical components. Have you changed that?

 

+1. Need much more info, like "lots of sensors", that could mean anything.

 

sorry, i changed-both temps-tps-iac-map-iat. the car runs good untill about 3 grand. if you pull in any gear around 3 grand it breakes up-sputters, i dont know how to exsplain.

i changed the plugs, wires, header geskets, t-stat, radiator, balancer. i drove it for a while and it was fine now all problems are back, rmps hang up around 2grand when stoped, if you give it a lil gas it will come down to about 900 and jump from 500-900 and almost die. it hesitates bad when you get on it likes it missing. its hard to start after hot, cranks and you have to give it gas..

 

Sounds like you replaced everything except the ICM (ignition control module). Like I mentioned, they are prone to heat-soak.

Also, if it hesitates to reach higher RPMs, might want to take a look and make sure your cats (if you have any) are clogged.

 

no cats lts and dumps. so try the a new icm?

 

I would.

 

Do you have any dtc codes showing up? Meaning is your ses light on?

 

yes a.i.r-o2's. no egr or air pump on the car. rear o2's are tuned out. the car is very hard to start after being hot....

 

That's a clear-cut symptom of a bad ICM. Hard starting when hot.

 

what are symptoms of a bad icm?

 

x2 agreed, i bet your icm is thermally breaking down.

 

Hard starts when hot, sometimes wont start it all untill it cools down. This is common symptoms of a failing icm.

 

they normally shut off ignition signal once heated up. but it is electrical so it can cause the engine to have a misfire tupe situation too.

 

similar to a burnt-out light bulb you can shake it,tap it etc. and it may come back on again but how long is undetermined time to replace it.

 

were should i get one from, how are msd optis and coils? that whats on there now

 

stick with ac delco!

 

I'm going to guess that you have a 97...10474610 is the GM part number. Don't settle for anything less than the Delco. Additionally, you will want to move the ICM farther away from the cylinder head, as that is the hottest part of the engine. Do a search and you'll find some information.

IMO, stick with the OEM optispark. The opinion is split on the MSD. Some people have problems with them while others have success. I am sticking with the OEM.

 

how do i know if the opti is good?

 

From what you have explained thus far, the ICM is what you should target first - not the optispark. It's relatively inexpensive. It's easier to diagnose a failing optispark if you know that the ICM is good.