Ok, ive searched around for a while and cant find anything to help.
I have a 95 LT1 6 speed ported heads, CC305, mac mids, dyno tune.
Ive been having this mid to high RPM breakup for 3 weeks now and it is now so bad that i cannot drive the car. Thinking the opti was bad, i switched to the delteq, but the breakup is still there. It will idle fine and rev fine til it warms up and then the missing and breaking up starts again. Note: When the car is missing and breaking up, the tachometer jumps around eratically. The car does have an LT4 knock sensor. There is no SES light and no trouble codes are present.
Also, Occassionly the car will not start at alll.
I have moved on to thinking that the PCM is bad or has a short. What do you think?
Im really just looking for ideas here on what to check/replace. Any help is greatly appreciated.
I dont believe its the optical sensor for the opti because the LED light on the Delteq box stays on like it should and there are no opti codes thrown.
Edit: Can there be codes thrown in the PCM but no SES light on?

 

that happened to me, but in a milder manner. it was present for quite a while, but it seems that it got better as i drove it, and it currently isn't doing it (knock on wood). sorry, i have no help for you

 

I noticed mine does this when the maf has gotten dirty. Cleaning it seems to clear up the problem.

 

Have you replaced the fuel filter recently? I had a problem a while back where I couldn't rev past about 4000 RPM. Replaced the fuel filter and all was good. Definately rule out the easy (cheap) stuff first.

 

What is the MAF?

 

mass airflow sensor, in the intake path just before the elbow going to the throttle body

 

How do you clean the MAF?

 

Q-tip and carb cleaner. some guys like using window cleaner. You VERY carefully clean the seensors with the q-tip. Just prespray the q-tip and wipe them down until clean.

 

so do you actually clean the wire looking things that go through the center in the housing? im pretty sure this isnt the main problem with my car because my car is not starting at all now. but i may try to do that later anyhow....i plan to get my friends laptop and scan for stored codes tommorow so maybe i will know something more then

 

IF you havent replaced the fuel filter lately do it first.
If that doesnt fix it, hookup a fuel pressure gauge and start driving. If the pressure drops when the breakup happens your pump likely needs to be replaced.

 

Like the other guys have said, it sounds to me that you have a problem with your fuel system. This would explain why it was choppy at higher rpm (lack of gas flow) and now that it won't start sounds like the system has finally crapped out. Check fuel filter, fuel pump, and possibly water in gas tank but that wouldn't prevent it from starting unless you had a **** load of water in the tank. Hope that helps

 

well, i scanned the car today using Freescan and no trouble codes were present....is it likely for a PCM to be bad without setting trouble codes? i got the car running tonite and took it for a spin, once it started breaking up highher RPMs i started to believe the fuel was cutting out....the only thing that makes me think its not a fuel problem is that when it misses or breaks up, it pops back in the exhaust, which i always thought meant unburned fuel.....o well, i on my way to the garage to replace the fuel filter and tommorow im gonna get a hold of my buddies fuel pressure tester and see what that tells

 

Check your TPS sensor and how old are your plug wires?

 

plug wires are brand new as well as the delteq coils and plugs.....any links or info on how to test TPS....sounds like its worth a try

 

Even though you said you scanned it, just for clarification I wanted to say that you can throw trouble codes without an SES light. The benefits of a scanner... I could tell you the resistance reading limits on the TPS, but I'm at school now and the manual is at home. Basically, most sensors have acceptable limits for resistance readings when you put them up to an ohmmeter. I'll post again when I get home and look up the limits.