hey guys, i rebuilt my engine the other year, barely drove the car last year because i needed tires. been driving it some this year but still not alot, need an exhaust, the car is too loud with a single 3" pipe out the back....

anyway, here's the basics of the car 94zm6
stock rotating assembly, new bearings/rings
heavily p/p stock heads
heavily worked intake, stock tb and intake so far
combo motorsports double roller timing set, hardened teeth
electric wp
edelbrock headers and straghtpipe
230/236 comp cam
promag 1.6's stock lifters hardened pushrods
aeromotive fuel system, sumped tank sy/ty injectors running at 60psi
some tuning done from borrowed programs

so car always ran fine, needs a dynotune other than that its good until lately

the problem
i noticed the other week it picked up a stuble from 5000-5500, figured maybe opti was acting up.
after i refilled the tank i checked it again, still there.
drove about 20 minutes away, checked it today it did it again, alittle worst. then it did it at around 2500-3000 easing along in third gear.. did our business and on our way home it did it again around 2500, started coasting with clutch in due to a stop coming up and it stalled, popped the clutch and it fired up and ran alittle before backfiring twice and stalling again.

stopped and tried to restart, it backfired again. waiting tried again, this time it fired, spit and sputter then died. that's all it does now, spit, spudder die.

so did my opti crap out or is it something else?
it acts like the timing chain skipped a tooth, but it's practically brand new. i don't think i've put more than 10k on it since the rebuild. if that.
could it be the maf?

most importantly how can i test these things to rule it out?

thanks, sorry for the long post.

mike

 

anybody?

 

I have a random high RPM miss and couldn't find anything wrong (plugs, wires, Etc.), but always had a gut feeling it was the Opti (w/ low miles). And it was the Opti, for what that's worth.

WD

 

anybody else? the thing that bothers me is the backfiring out the exhaust

 

I'd say its dead.. I had one crap out on my car.. I was running in the driveway just fine.. Then i started to stumble lower and lower then died. Tried to fire it back up. It fired, started to stumble again then died.. One more time and all it would do is spit and sputter and not fire at all..
Bought new one and its been fine ever since!

 

If you remove the Opti, remove the cap and look it over carefully. I had a rotor screw on a GM Opti fall out and the rotor was loose. That was all that was wrong with it. Other than the loose rotor, the GM Opti was OK. Also had that happen on an MSD Opti (loose rotor screws).

WD

 

Thats true, forgot to mention that. Had it happen on a buddies formula..

 

With both the GM and MSD Optis (new units) before you install them, you should use thread-locker on the rotor screws and ensure the screws are tightened correctly.

Or, you'll end-up like this.

WD

 

^^ True story. It happened to me too.

 

thanks for the tips!