texasTA

A little quick info: LIttle brother's car is a 1996 Z28 with LLoyd Elliot heads, Hotcam kit, Longtubes, offroad ypipe, electric CSI H2O pump, OVC wires, built tranny, 2500 stall, K&N FIPK. His car has I believe 107000 miles on it.

Here is the problem, At about 60000 miles he had a factory replaced under warranty OPTI installed at the Chevy dealership. That opti lasted until about 105000 miles. He put on heads/cam and his factory replaced opti went out in about 7 months, maybe 5000 miles. So, we figured it had 45,000 miles on it, it probably needed to be changed.

We installed a brand new opti from Jason Cromer. No problems installing it, and the car ran great for about 2000 miles or so. We just went for a drive today and the car felt fine for about 30 minutes. He went to give it some gas (3/4 throttle) on the highway and it got to going pretty well. Then we slowed down and upon the next throttle increase, there is the BAD OPTI hesitation/stumble at 2500rpm.

What could be causing his car to eat up these OPTIs so quickly? I thought I had read something about a dowel pin, but I don't remember what that was about. Thanks guys.

Oh, and we should be able to get a replacement opti through Jason Cromer, since the opti didn't see a year or 12 months, correct?

96Z28TealM6

I know I had a stumbling problem too and found out it was the egr valve

texasTA

He has absolutely no emmisions stuff on his car. !AIR , !EGR, !CATS. ???

S.J.S.

Are you sure its the Opti and not like a vacuum leak somewhere? I'd eliminate other possible culprits before the opti.

And I highly doubt you'll get a replacement if you used it for 2000 miles. Worth a try though.

97WS6SCharged

Have you checked the dowel pin length on the cam? If that isn't correct it could eat up Optis pretty quickly.

texasTA

We can check vaccuum leaks, but I am pretty sure it is something ignition related. It ONLY happens at 2500rpm, before 2500 and after 2500 the car sounds perfect just at 2500rpm. And with teh longtubes, cam and cutout you can definately hear the stumble. I would probably call it a stumble, because it is not very "quick and gone" like a miss. It is kind of like "start missing and the engine sounds like it is stumbling". We will check all vaccuum lines and probably put the ignition coil out of my car in his to rule that out. But I am pretty sure it is OPTi, since his car sounded JUST like this before we swapped out his opti last time.

texasTA

I might sound like a complete dumb a$s, but how do you get to the dowel pin. He had someone install his cam for him. Is it just under the timing cover/chain or much more removal? Thanks guys. This is kind of like what I thought it might be, but the guy who installed his cam has done a couple of LT1 cam swaps.

mineralwater

this is a shot in the dark, but did you do plugs/wires, and a new coil/coil wire along with the new opti?

I've heard that a bad coil can kill the opti pretty fast.. not 100% sure if this is true or not, does anybody know for sure?

texasTA

I hate to say this, but the only thing we did not change with the last opti was the coil. So, you think that could be the problem? We did do brand new plugs/wires,coil wire and opti. I hope something as little as the coil didn't cause this problem again.

slopokrodrigez

New parts do not carry a one year warranty. Especially electrical parts. The opti can be understood by being broken into 2 sections. The distribution section that sends spark to each plug just like any other distributor. The other section is the optical encoders (hi and low resolution) that the PCM uses for a variety of tasks.

The optical encoders send a square wave via wires to the PCM so it can do several things regarding engine operation. It is doubtful you could cause any damage to this section since it is powered by and responds to the PCM. There is no way to say for example increase the voltage supplied to the encoders to an unsafe level. The optical encoders have a problem dealing with moisture however and that is why after 94, GM went with a vented opti to help keep it dry inside. Here in could be where you're having a problem. Check to see the vent lines are not damaged and are connected correctly.

The other area in the distributor that could be damaged is the plug wire/ contacts/ rotor section. Again not much possibility of damage from the user. It could be argued that using a more potent ignition could burn out contacts on the rotor or cap at a greater rate than stock. I haven't seen definitive proof of that but I have heard of impedance miss match problems between some coils, ICM's and ignition units when some after market components were mixed. This wouldn't cause premature of the opti but rather the ignition components themselves.

It would be prudent for you to study the opti system and become formiliar with its operation and testing procedures. Many test like the optical signals can be checked for basic operation with a digital volt meter. We can help with that if your ready to check it.

You should also check for spark at each plug. You can do it with another plug so you don't have to actually pull each plug but rather just the wire.

Good luck to you

Mtrhds94Z

Make sure that the opti venting lines are in correct places and the correct lines[especially the 'flow restrictor']
You dont want full maniflod vacuum, it will suck the distributor cap in slightly, breaking the rotor..

Brandon 95 Z28

Actually you should be able to warranty out the opti if it is less than a year old. I have done so, and so has my buddy, you need a warranty info card from the parts department, fill it out, then ask for a new one when you bring in your old one.
Brandon

QCKZ28

also high rpms shorten the life of the opti....
auto zone has one that carries a lifetime warranty.
jesse

fast00xtreme

This is the guy who has the busted car:
It also misses from 5500-6400 real bad. It doesn't have the 2500 rpm miss anymore, just the high RPM miss.

97 RedSS

yeah..usually high rpm miss= bad opti..Check your cam dowel pin length and see if maybe its too long. Also, check the cam retainer plate and see if the torx bolts are loose which would be allowing the cam to "walk" forward...

Im the guy who purchased the Air Compressor from you or your brother
Im putting it to good use over here

G'Luck on the car...

Cody