figure i'll give it another shot

car misses around 5800+ i've been fighting it for many years now with no luck.
changed plugs & wires many times, 3 different opti, 2 different ignition boxes, 3 coils, 3 different valves springs, 2 cams, 2 different set of heads, 2 ecu, 2 opti harnesses, ignition modual, fuel pump, injectors....
not all of those thing i changed was to get rid of the miss but just giving you and idea of what i've been through

plus im sure i missed something


http://www.mofbody.com/blkchevyz/chsheads.jpg
http://www.mofbody.com/blkchevyz/fmsdyno.jpg
http://www.mofbody.com/blkchevyz/webdocs/dynosmall.jpg

 

do I dare say LT4 KM ?

 

i know its not knock becuase i disabled the knock retard, my cam was driving the computer nuts

 

are you running a stock opti and have you upped your rev limiter

 

Does sound like rev limit.

 

did you change the cap and rotor when you changed the opti's? My high rpm miss was the cap and rotor caused by my msd.

Valve float maybe?

 

I was thinking the stock rev limiter as well as soon as I read your post. I saw stock computer, self tuned, did you raise it by chance?

 

put 3 differnt opti's on it. so i think that rules that out

i know its not the rev limiter becuase both the ecu and accell are at 7k

i wouldnt think it would be valve float, had 3 different sets of springs on the car
and my old head with the springs and 306 cam are on another car that doesnt have this issue.

 

Have you tried taking the ignition box off? Those things are notorious for causing problems on optispark cars.

 

yeah i ran it with 2 different accel boxes, then removed it completely

 

What makes you think it's a miss? The PCM will usually flag a a true misfire, but there's a lot of forms of high rpm stumble that don't throw any codes.

 

Did you replace the wiring harness? If its something in the harness, changing all of the things at the end wont help it at all.

 

miss, stumble... call it what ever you want. my cars a 94 so it doesnt have the crank sensor... so it wont know throw a code


thats the only thing i havent tried, that i can think of. i've just thrown so much money at it i'd hate to keep doing it.

 

I have the same problem with mine, but I haven't tried as many things as you. Also, my miss/stumble starts at 4500.

Here is a list of what I have changed:

plugs (NGK TR6, and Autolite 104's-gapped to .032)
wires
2 opti's (Both new GM units)
opti extension harness
engine wiring harness
ECM
Crane HI-6 with LX92 coil
stock ignition

I never felt the problem before I put the blower on (it's a ported heads/CC306, stock bottom end), so I took the car back to NA, put the 30# injectors back in, along with my other ECM with the original Ed Wright tune. Took it for a spin and I didn't feel anything. Then I put it back on the dyno (NA) and the graph looked similar, but not NEARLY as bad. So it was doing it NA, but I couldn't feel it. Looked up some old dyno sheets (from 3 years ago) and it didn't show in those graphs.

I'm at a loss too....pulling my hair out trying to figure it out.

 

Is your timing too aggressive? What kinda timing are we logging at WOT?

 

I have the same problem. I have a MSD 6A, with a msd coil. My car has a miss at just over 6k. I shift the motor at 6400, and ususlly around 6100 and 6300, it feels like the motor misses on 1 or 2 cil. I have put on a new opti cap/rotor, new wires/ plugs. I plan on putting on a new opti this winter to see if it fixs the problems but i have a bad feeling it will not.

 

The NA tune from Ed Wright had/has something like 44* in it at WOT, but the blower tune only has about 17-18* in it.

I am seeing 0 knock retard.

 

im running a decent amount of timing, dont remember the exact number.
but i have tried pulling alot out and it still missed.

 

does yours rev past where it misses?

 

check the grounds all the grounds, had mine come loose on the coil and had a miss, also what is your spark plug gap, are you blowing the spark out?