It's been a very long time since I posted here, so with that in mind I'll make a very long story short.

I have a 1995 Caprice/Impala (9c1). It's has a 1995 Camaro LT1 T-56 drive train. The original work was done on it back in 06-07. The drivetrain is stock & the motor was rebuilt back in 08. Just rings & bearings. Less than 20K miles since the rebuild.

Here is the breakdown:
Stock Camaro 95 LT1/T-56
4.10 gears.
Pcm for less tune.
No cats or EGR. Block off plate. It's emissions excempt.
Has O2's one per side. New back in 08.
Headman headers, 2 1/2 exhaust, H-pipe. Summit turbo mufflers.
New fuel pump walbro 255, new harness & relay. 2 months ago
New Opti spark, still have 2 good ones. (This is not the problem)
New ignition EVERYTHING (all replaced within the last year)
Map was replaced TODAY.
Iac was cleaned last summer & the TPS (new) was drilled, metered & set to specs.

I have NOT replaced injectors, or the MAF. Everything else has been replaced & in some cases 2-3 times. Most everything listed above has less than 10 miles on it.

THE PROBLEM:
Some kind of weird miss. It will start, Idle, even drive. It has a miss idling. It loads up slightly while idling. Drive it and that's when the problems begin adding up. Just at cruising speeds (partial throttle) it's starts bucking slightly and feels like you're pulling a trailer behind the car and the exhaust spouses strange, not backfiring, but trying to unload. Get after it (WOT) and it will respond with no backfire or real hesitation other than some noticeable power loss.

None of what I described is consitant behavior. It doesn't seem to matter if it's warm or cold out, if the car is warm or cold. Sitting idle it will hesitate and stumble upon a light tap of the pedal, other times it responds instantly like I would expect it to.

I've done a hell of a lot more than is listed here & have been chasing this gremlin for a few years now. Ohmmeters, test lights, new parts & HOURS UPON HOURS of forum reading all over the net. I'm stumped plain & simple. At this point I don't mind saying I feel a bit defeated.

You Camaro guys seem to have it nailed down on problem solving, hence me posting here. I apologize if this thread is in the wrong section & that the car isn't a Camaro but I'm desperate.

Thanks in advance for any & all advice.

 

what kind of spark plugs you using? have you had the injectors cleaned and flow tested?

 

Craby, hey buddy. You're actually the one that helped me a few years back about picking a opti from one of the venders here. Thanks by the way.

The plugs are just cheapos, nothing special. The injectors are stock 19lbs off another caprice & no I have done nothing with them. Thoughts?

 

camaro lt1 uses 24lb injectors, i think i got some around here somewhere. need cleaned and flow tested though. you might try some better plugs.

 

I'm pretty sure I could pick up used set of injectors around here fairly cheap too. Thanks for the offer & info. I read up on plugs last night, looks like the way to is the NGK iridiums. I had the car scanned last summer & codes that came back was the knock sensor, replaced with new pig tails too.

I'll grab some NGK's & Injectors today & let you know.. Thank for the help Craby, I appreciate it.

 

way cheaper to have yours cleaned and tested. i had my new 30lb injectors done and even new one of them was not matched well with the others. would work just not matched good. did the tuner recomend any specific injector? better tuner would be solomon at lt1pcmtuning

 

I went & picked up the NGK's, new MAF, 2 new O2's, new IAC, and am on the hunt for some injectors. I was told if none of that solved the problem I would be reimbursed. I hate to do that way, but as I said before I'm desperate. I will systematically install & check, rinse & repeat to see if one of those was causing the issue. I installed the new MAF, moments ago, started it, waited for the idle to come down & tapped the pedal. It fell on its face for a second then revved.

"Solomon at lt1pcmtuning" That's sound advice, I'll go check that out and get ahold of him. At this point I'm almost wondering if it isn't the pcm. Initially my tuner/tune was a Q&A sheet filled out & mailed. They came highly recommended by the Caprice/Impala guys back in the day. I only ever spoke to him once & needless to say it was pointless. The car had ran rich from day one.

 

also wait till its really dark, start er up and have a look under the hood. if you see a light show around your plug wires they need replaced.

 

Well I installed everything listed over the wk-end to no avail it seems. Any other suggestions?

 

is the pcm from camaro or stock imapla? was it manual trans before?