Opti Time Again? You Tell Me. . . . . .

[97LT1Z28]

I've got a severe (intermittant) miss at idle - under load and while accellerating only after the engine is warm.

In chasing this problem down in the last six months, I've replaced the plugs, wires, ignition module, coil, opti (autozone aftermarket) Injector #5 and it still has the miss.

I had the dealership hook it up to a scanner and the techs said that when the miss was happening, it's missing on Cyl #5 and #7. Everytime the motor hesitated or shook, the scanner showed a miss on 5 & 7.

Should I get a GM opti and replace it? Or am I barking up the wrong tree?

[97LT1Z28]

anyone.....?

[Injuneer]

If I understand the problem, you had the intermittent miss BEFORE you started the parts replacement, and you have the exact same miss AFTER you replaced all those parts.

The current trip to the dealer localized the problem at #5 and #7. Did you have a similar scan done BEFORE you replaced all the parts?

Did you replace the complete Opti, or just the cap/rotor? Did the problem clear up at all after the Opti replacement, or did it continue to miss from the first day you replaced the Opti?

If it had the same problem before the parts replacement and after the parts replacement, I'd hesitate to assume its the Opti. Its more likely something you haven't replaced.

[97LT1Z28]

If I understand the problem, you had the intermittent miss BEFORE you started the parts replacement, and you have the exact same miss AFTER you replaced all those parts.

The current trip to the dealer localized the problem at #5 and #7. Did you have a similar scan done BEFORE you replaced all the parts?

Did you replace the complete Opti, or just the cap/rotor? Did the problem clear up at all after the Opti replacement, or did it continue to miss from the first day you replaced the Opti?

If it had the same problem before the parts replacement and after the parts replacement, I'd hesitate to assume its the Opti. Its more likely something you haven't replaced.

I replaced the complete opti plus the cap & rotor and it did continue to miss the day after the opti replacement.

Before the opti, my laptop scanner program would show a random miss. After the opti, the dealership shows the miss on 5 & 7.

I wonder If I got a bum opti . . . .

I think I'm going to have the opti replaced with GM parts and then go from there . . . .

[BmXRacR96]

I tried an aftermarket Advance auto distributor, 3 times. Similar problems after a few months. Each time buying one i noticed the electronic portion was made by different manufactures in the 3 units. Which is a sign of a cheaply made P-O-S. The third one worked til the rear seal fell out and was spinning around. Then it missed... Now i have a Delco complete unit.

Stay away from aftermark replacement Opti's. I had no luck with them. Use the GM Delco unit. $100-$150 extra is worth saving you hours of time.

Doug

[Injuneer]

Is it possible you have the injector harness wires switched on the #5 and #7 injectors?

Something is saying this is a problem related to #5 and #7 only.... crossfiring, wires switched, something like that.

[Joe 1320]

Just a thought, pull the car into a dark area and open the hood. Run the engine with an assistant and check for any blue glow (evidence of arcing) around all the plug boots and coil. I'll bet a dollar that you'll find something arcing to ground.

[Dave Vince]

Rebuilt optis?

Tried one of those stinkin so called rebuilt OPTIs from Auto Zone. The piece of junk gave me the exact same problem I had before I changed it. Cutting out at 3500-4000. Put in a GM replacement and it cured the problem.
The spark plug wires jumping to a header, where it has burned thru can also be the cause of your problem, low speed miss. Try Joes solution for that one. MSD makes a good set of wires for the LTs.