mdtoren

So, been driving my 86 Iroc after finishing up my Carb swap and I am having the following issue and need some thoughts on where to start digging. Car is a 305, originally TPI swapped to carb and has edel performer manifold and holley street avenger 570cfm, Comp Cam 260h cam, 700R4 trans.

I am having a pretty decent stumble / miss fire just off idle during acceleration. Ive noticed it gets worse the longer I sit, a simple stop sign is less of an issue, a longer stop light creates more of a stumble. It appears that if I give it more gas it corrects the stumble and while cruising there is not a miss/stumble. Ive also noticed that at longer lights while idling Ill start to get a miss fire in the exhaust at idle. Car never dies and no stumble when rev'd in park/nuetral.

Im leaning towards carb tune issue because I never tuned the carb during the swap bc it ran, but, Ive been reading up on Torque converter issues causing spark knock, and I am leaking some trans fluid when the car sits for longer than overnight which went on long before I carb swapped.

MSgt Luttrell

It sounds like the carb is loading up at idle, in gear. Try doing an idle drop adjustment with a vacuum gauge and double checking the initial timing to make sure it's not too far retarded.

mdtoren

I will try this, Thank you!!!!!

zed-028

i had a vacuum leak that pulled this crap on me a year or so ago.

MSgt Luttrell

If that all checks good, check to make sure you are not running too much fuel pressure to that carb.

1987L69

did you switch your distributor with a non computer controlled one? if not that could be your issue

mdtoren

Yes, running a non computer distributor, I thought it might possibly be a spark issue, but have ruled that out.

mdtoren

Right now I am running 6psi from the regulator to the carb, does that sound too high?

1987L69

no, that sounds perfect for carbs, is that at idle or WOT?

zed-028

checked the pcv valve lately?

recently had the stumble scenario at the lights, ordered a new one and pulled the old one to compare, completely screwed. might not be a bad test for $5

mdtoren

Idle, havent checked WOT.

mdtoren

Im not currently running PCV, just running 2 breathers instead. Any chance a PCV set up would fix this? I was under the impression either set up would work, but the PCV was just "cleaner"

zed-028

nah probably not, the valves going out do all sorts of wierd stuff.

MSgt Luttrell

4 to 6 psi should be fine.

RedLeader289

iTrader: (2)

Check your ignition control module (ICM) inside the distributor cap. Whenever mine is going out (these cars eat them like candy) I get the symptoms you describe.