My husband's 94 Camaro Z28 runs rough. It acts like the timing's off, but it's not. It's an automatic, but when accelerating we need to manually shift it. It sounds like the car is going to die if we don't. It will also idle high sometimes. We believe it may be a couple things. We may need to replace the o2 sensor, and I was wondering about the voltage. I heard that if the voltage is off, it may cause the car to run like crap. It has 127,000 miles on it. It belonged to my mom and dad, but don't think dad did any major maintenance on it, just oil changes and such. It's been like this a while. We're slowly working on it, but I want to get it running OK for a while before we start on the body work (needs dings repaired and a paint job). Plugs and wires were changed. Please let me know if may be anything we could have overlooked.

I miss my '75 350! So much easier to work on than the computerized crap now!!!!

One thing that can happen is the timing chain will wear down the cam gear or stretch and retard the valve and ignition timing. Vacuum leaks develop over time as time and heat take it's toll. Look for hoses that are cracked or have come loose. Valves will buid up heap of coke on them from oil burning onto the back of the valve. Search the archives for seafoam for a quick fix that may or may not help.

You say the timing is good, but you can be fooled. Harmonic balancers often slip throwing the 0* mark way off. the only way to be sure is to use a piston stop to find TDC and make certain the mark is on 0*. Follow the manufacturers guidlines to set the timing - should be on the emissions sticker under the hood. You probably have to disconnect a wire to set the timing.

In general though, it's probably tune-up time. Do a compression check on it, warm and cold. Cylinder pressure should be above 140 and each cylinder within 10% of one another. Be sure to prop the throttle plates open a bit, and it helps if you remove all the plugs.

If the compression looks good, give it some new plugs, wires, cap and rotor. Those things will make a significant difference.

'94 Z28 would have an LT1--there's no timing adjustment on the opticrap.

The first thing you want to do is dump codes out of the PCM. I think some auto parts stores like VatoZone will do it for free. The codes it has thrown may give an indication as to what's wrong.

My first guess is a bad opticrap.

Jon
I'm not automotive. I try to keep an eye on threads like these so I can learn some about newer auto electronics....names mess with me sometimes... opticrap... what is that please? Obviously a newer better ...PCM?
Thanks!

tim, what jon is refering to is the optispark, it is basically the distributor of the lt1 motor. in 93 and 94, the optispark had problems because gm didnt have a vent tube to release moisture causing it to corrode and missfire. i had a 93 z28 with a optispark problem and the engine would miss going up hills and sometimes even cut out, long story short, i traded the car before it actually went. if im wrong about the optispark, please correct me guys.

Yep, "opticrap" means OptiSpark, the very unreliable cam-driven optical-trigger distributor GM used on the GenII (LT1) smallblocks. Just noticed that Google has more hits for "opticrap" than OptiSpark though :).

PCM is Powertrain Control Module, aka ECM (Electronic Control Module or Engine Control Module), aka ECU (Electronic Control Unit or Engine Control Unit). Some cars also have a BCM (Body Control Module).

Here's a lot of acronyms the 4th Gen guys use:
http://www.ls1tech.com/acronyms.html

And here's a really extensive list I just ran across:
http://www.cs.purdue.edu/homes/nbheck/automotive/acronyms.html

Thanks guys

does that lt1 have an electrinic egr???i`ve had problems with carbon build-up that formed into carbon balls, and hung the pintle open on the egr...this can also cause a high idle as the ecm will try to compensate for a lean condition...