frito1

iTrader: (12)

My friend has a '94 Z28 M6 car. It is completely stock. He gets a hesitation or stutter under WOT(or it is most noticeable at WOT) at low rpm or basically off idle with a load on it. The car runs great the rest of the rpm band.

My search said that a bad O2 could cause this. He has no SES light.

My search also said it could be the coil arching off the valve cover. He checked in the complete dark and there was no arching.

He has new plugs and wires on it. No waterpump leaks

With the bad rep of the optispark, we were leaning towards that but hate to just start throwing parts at it until we get have a better idea what the problem is. Can you point us in the right direction?

Thanks

97SSCamaroGuy

iTrader: (1)

My car did the same thing and it was the optispark...I ended getting a Dynaspark!

frito1

iTrader: (12)

And if it is the optispark, what is the best unit to go with... OEM, MSD, etc?

frito1

iTrader: (12)

Ah, I think I was typing at the same time as you were... just a little slower! haha

Who makes the Dynaspark? Does a vendor here sell it? Is that all you needed to fix the problem?

Thanks

frito1

iTrader: (12)

bumpity

frito1

iTrader: (12)

Can anyone else give anymore insight on this issue? Seems it could more things than just the opti? My search hasn't gave me a direct answer to this problem

LM97Z

iTrader: (4)

Good luck trying to get an exact answer to a possible ignition problem, its hard to do, i will say this, check the OBVIOUS 1st., don't just start tearing into things, because it may not be the Opti, what i've been told from a few sources is 1 sign of an Opti giving trouble is hard/harder starting, but thats not ritten in stone, so start checking fuel pressure/filter, plugs/wires, air filter/vacuum leaks & so on 1st.

97SSCamaroGuy

iTrader: (1)

Dynasparks run pretty expensive. Check out www.dynaspark.net
I got mine remanufactured for $399 and it works great. Everything is built to perfection.

I8ASaleen

iTrader: (9)

Isn't Dynaspark falling on hard times right now? Watch out.

To answer the question I'm with LM97Z on this one, also get the OBD scanned just to be sure you don't have any codes b/c it will store them (you want to watch for a low res pulse code or a high res pulse code for the opti).
You might want to check out the coil as they are known to wear out, and def check the fuel filter/pressure.

Edit: I had something like this happen and it turned out that I had a huge vacuum leak, one of the hoses that comes off of the intake manifold bends a wierd way and inside of that bend it was completely corroded and leaking (though you couldn't see it)

ThoR294

iTrader: (6)

also, your car is OBDI. the check engine light comes on whenever it feels like it, really... soo best thing is to hook up a scanner and check out your data, if nothing visual is wrong, like a vacuum leak, bad fuel pressure, etc.

Marc3.4V6

iTrader: (1)

^^or not at all, a scanner is generally useless on obd1 unless you've got a code.

Pretyflywiteguy

OBDI is far less sensitive than OBDII

ThoR294

iTrader: (6)

a CODE scanner is useless, but a SCAN TOOL that gives u live data will help.

AChotrod

iTrader: (17)

Ill bet its a dirty or bad MAF sensor.
K&N oil is known to cause this if the filter is over oiled.
My truck just had the same exact problem, I tried everything wires,plugs cap rotor,fuel pump fuel filter, fuel system flush, and then all types of injector cleaner etc.
It ended up being a dirty MAF sensor. It wasnt broken so it didnt throw codes just made the truck run like **** ride when you would start driving then it would be fine once you were moving. Under wot it would stuter then start running fine.

Formula350

iTrader: (3)

Or a scanner like mine that tells me the outputs of the sensors. And no, mine isn't some $3K huge screened Snap-On. It's a craptacular $200~ (back in 02 or so when it was new) that is almost of No-Name brand.

The TPS could be reading too low and it stumbles due to that. See where the closed throttle voltage sits, and where WOT sits. If it's below .58v you're going to want to mod the TPS by ovaling out the holes to make it "adjustable" and then move it to around .65v. IDEAL WOT voltage is over 4v and best is 4.5v, but I've not seen 4.5v attainable w/o a enhancer module, so really anything over 4v is at least sending a WOT signal to the PCM.

That's the cheapest thing you can do, save for swapping parts with your car (not the opti, just other ignition parts like ICM and Coil).

z28_theantirice

iTrader: (2)

Datamaster way to go... But still might not help you figure this out...

Marc3.4V6

iTrader: (1)

Oh, I was told scan tools for the obd-1 couldn't help find a misfire.

Formula350

iTrader: (3)

You didn't say MISFIRE! -_- Correct, OBD1s can't do specific cylinder misfires, at least any GM systems I've looked at.

frito1

iTrader: (12)

Sorry I lost track of this thread. I didn't know you guys kept posting on it. It seems really odd to my buddy and I that you guys aren't saying "opti" all the way. This isn't a coil or plug wire problem. That would be a miss all the time under load. This is just a very small, low rpm, stumble under hard acceleration. A magazine he has, says the opti is one of the common things to go bad on an older LT1. So he feels pretty confident that is what needs replaced.

Can you tell me what a bad or going bad opti feels and acts like? Is a factory GM opti the best replacement while being cost effective? He isn't into performance as much as just getting a quality part. Will the vented '95 opti work on his car?

Formula350

iTrader: (3)

I haven't been in a bad opti car, but I think we all try not to just yell "opti" when there could be other things that COULD do it. It's also because it's a total PITA to do an opti