My 93 Z28 seems to have issues once it's warmed up and running after about 20 minutes. Any help or suggestions will be appreciated. When I hit 2000 + RPM's it begins to surge and almost feel like it is backfiring. None of this happened until I disconnected the battery and replaced the AC Compressor. I have checked & rechecked spark plug wire connections and infact they were replaced less than 1 year ago. I have disconnected the battery several times. Is it realistic to believe my Optispark failed once I disconnected the battery, when it was working and running great prior to the AC Compressor install? Could it possibly be a sensor problem? Knock or Idle Air control. When I stop at a light the RPM gauge is going crazy bouncing erratically and even at maintained speeds. No warning lights have came on. The car has 132K miles. I am really at a loss here.

 

Are you sure you didnt pull a wire loose on the opti when you replaced the A/C?? (see if they are all snapped on tight)

 

Make sure you did not disconnect the any of the vacum lines. On a 93 there is one that goes of the intake and goes into the wiring harness. Make sure there all tight and not cracked either.

 

That sounds like an ignition problem to me. I had a Opti act like that once, I also had a burnt wire that acted the same way.

 

dont forget about the ignition control module. id check the other parts first as i think maybe it will be something more simple. besides the only way to check the module is to replace it and at 70 dollars i consider that a lot to pay for a maybe.

 

Are you throwing any codes and do you have access to a scanner?

 

it might be an opti! mine did some freaky crap too when it went south earlier this year on me.

 

Thanks! I rechecked all wires connected to the spark plugs & opti on both sides. I am thinking it may by the wires even though they were replaced a year ago. I have a jacobs engineering coil and had taylor 8 mm wires. Unfortunately endinng up trashing the taylors and went back with original GM. What's weird is that it does not start acting up until it gets warmed up (after 20 minutes or so)

 

Thanks, I did not know of this. Could be it, I hope

 

Actually, all of these suggestions are good. I hope Autozone will have an OBD1 Scanning tool, but I do not appear to be throwing any codes. 93's were still a speed density car. Ignition Control Module? Would that throw a code? And would the car still start and run fine for 20 mins? I have the Hypertech Stage II drag chip. Will this affect the scan readings? All I know is I am sick of the car doing this crap....

 

Easy way to check codes on a 93. Take a paperclip, and put one end into the upper right ALDL port, and put the other end in the ALDL port to the immediate left of the first one. You should have the two top row right side ports "jumped" together with the paperclip.

Turn the Ignition ON, car OFF. DO NOT start the car. Your fans should come on, and your SES light will begin a series of flashes. First thing it's going to do is this:

FLASH long pause FLASH pause FLASH longer pause (repeat 3 times)

This is DTC 12, which is showing that the computer is in diagnostic mode. After the third time flashing DTC 12, the computer will flash any stored trouble codes in the same fashion: Series of flashes for first number, long pause, series of flashes for the second number, longer pause, repeat 2 more times.

Once all the codes have been flashed, the computer will start flashing DTC 12 again. Turn car off and remove paperclip jumper.

Write down the codes and post them up here, as I have a 93 service manual and should be able to help.

 

Absolutely too cool! I went by an autozone today and had them to pull the codes for me.

I have two codes: Code # 66 and Code # 35

I am extremely curious to know so I can solve this problem.
Please respond asap...
Thanks,
Jim

 

Have a look in my sig at the link titled "Got a problem or SES light???" In it you'll find scans of EVERY DTC in the service manual for 1993, including descriptions and diagnosis charts. That should get you up and running in no time.

*Edit* this is for the 93 right, because my service manual doesn't have a DTC 35!

 

Thanks again! I disconnected the battery, ran the 93 Z for about 45 to 50 miles. Did the paperclip and pulled these codes. 36 and 61. I checked the codes by the link you gave and will somehow perform the tests. Thanks a million. I tried a search to find the 1993 Camaro / Firebird Service manual and came up empty. Do you happen to know where I might be able to purchase one?

 

That sounds more like a spark plug issue then a opti...I know when my opti went out it was doing it at all RPM's not just at a certain point...when I had a bad spark plug it would do it at certain RPM's thats just my $0.02

PS...it could be a vaccum leak now that I think about it too, I know when I had 2 vaccum leaks my RPM's were jumpin around like crazy even with I gave it gas...

 

I picked up mine on Ebay a couple years back for $40. Keep an eye out on there as there's one seller who deals almost exclusively with dealer service manuals.

 

I will continue to check on Ebay.... Hopefully I can pick one up that cheap as well. Question. I was tinkering around on the 93 today. A Jacobs Ultra coil was installed on this car in 1994. I noticed the black & red wire ran to a splicer plug or distribution block of sorts. Then back out. Same wires and then to the wiring (probably to the ECM) I noticed the block itself was not mounted. I believe it could have been upside down and possibly shorting out. Also, with an after market coil, should I have the Ignition Control Module plugged in or not. I believe it was plugged in before, but I am not 100%. Do you have any knowledge with this?

 

These two wires, were they going into and coming out of a small black box located to the right of the coil (in that general area)?? If so then that's your tachometer filter, so don't disconnect that box or your tach will read funky.

With ANY aftermarket coil, you will have to keep your ICM plugged in, or the car won't run.

 

I believe I know the black box you are talking about is located more toward the Ignition Control Module and Stock Coil. The particular box or more like a distribution block was located more toward where the stock air filter box would be located. This car has a MTI High Flow set up with a K&N cone style that actually mounts under neath in the hole where the original would get air. This distribution block was somewhat shoved in between the Antilock brake system and the inside fender or sheet metal on the driver's side. Strange to me as the distribution block has two wires running from the Jacobs Ultra coil then two wires starting again and going into the the wiring looking to go to the ECM. Unless these two wires run underneath the coil. I have not pulled the coil out yet to make 100% sure. It appears to possibly be a pain. I cannot explain enough how I appreciate your help...

 

Hmmm.....I don't know which one that one is then. The only major junction I know of there is a S113 which is a ground junction for a lot of accessory items. Give me some time and let me look through my service manual electrical schematics and see if I can come up with anything. I need a good starting point though. Can you make absolutely sure that the two wires going in are coming from the coil wiring setup??