my ta has a miss around 2800-4200 rpms. I dont have it at wot but it dont have in power. Its got new opti, icm, plugs, wires and ive went throw the valves again. Ive changed the intake from a stock 1 with a 52mm tb to a ported with a 58mm tb. I havent had it retuned yet. Could this cause the miss. Thanks

 

DID you also put a 58mm t.b on it as well or not? Cuz if you did put a 58 tb then thats your problem, without the retune.

 

Throttle body causing a miss? No

What kind of opti did you put on? Check out the opti wiring harness, peel back the loom and look for damaged wires or any signs of corrosion.
and TEST THE COIL.

 

I have a extra opti harness if you wana try it see if it makes a difference and also a extra stock coil. Also i still say change those plugs back out see if it changes. You said it started missing after you changed the plugs correct?

 

gm opti. its got a new wiring harness. its got a msd coil on. its been on for 2 years. could it be a fuel reg. its still the factory 1 from 94 lol

 

was doing doing it b4 i think. i will change em and c wat happens

 

try the stock coil if you still have it. its definetly worth a shot. i had problems with a misfire from a 'faulty' msd coil on my formula. good luck.

 

also pulled the plug after a wot pull and they look like there brand new. could this be a fuel problem.

 

did you tune for the 52mm throttle body or not?

 

it was dyno tuned with a stock intake and 52mm tb. its now a 58mm tb and ported intake. could that make it have a miss not being tune to the new intake and tb

 

It needs to be tuned. Your on a tune for a 52mm not a 58mm. Thats part of a problem if not the entire problem. I had my buddies car that had the same issue, then he put back on his 52mm t.b and the problem went away.

 

I don't understand how a TB difference of 6mm could throw off the tune enough to make it miss??? I could see how in off idle positions that your MAP may be a little bit higher than stock due to less resistance in the intake tract obviously leading to less vacuum which would effect your VE tables because of the difference in MAP but unless you are running SD that shouldn't really affect the way the car runs. Your MAF should still be reading an appropriate amount of air if it was calibrated with a 52mm with his current H/C setup than the computer should also be able to compensate for such a relatively small change to the airflow characteristics of the motor. As I understand it, the difference in throttle bodies has more to do with automatic transmission tuning and idle air flow than anything else. I am not exactly sure what effects it may have as I have only recently began tuning and my car is m6 but I do not think that going from a 52mm TB to a 58mm TB wouls give you a miss at mid rpms

 

yea i was thinking the same thing. I could see it being alittle lean but not a miss.