My 93 LT1 starts up fine. Runs rough, Sputters a little when cold and then when it warms up it gets rougher. Occasionally it will backfire. Not bad but noticeable. The backfire appears to be only on the right bank. I changed spark plugs (Cheap Bosh ones) and replaced the O2 sensor (Bosh). It does not throw any codes.

Had some experienced mechs at my place of business check out the fuel injectors and they were fine. The mechs seem to think based on the rough idle and a smell of fuel that it was the Opti going bad. My question is this...Would an Opti going bad only affect the right side?

 

Only if the plug wires on that side some how were loose fitting on the opti sockets. I had one that was not seated and it caused an arch that caused the opti elctrode to melt away and losing connectivity consequently a miss. What you describe could be the opti. I just put a new one on my 94 this past weekend, runs super now. Mine started to miss after it came up to operting temperature. I suggest checking the primary wire to the coil, I've seen those corrode. That would of course effect all cylinders. Have you checked for codes? Good luck.

 

I just had same exact thing happen to my 93. ( Same symtems) Started to look around and used data master to to find out driverside O2 was running extremely rich. The problem turned out to be on the bottom side of one of the plug wires was laying on the header and grounded itself to the header. Closely examine all your wires. Most of the time these problems are caused by either opti or coil.

 

You do have some opti like symptoms except for the rich condition which I don’t think the opti would cause. How did you determine the backfire was just on the right side. I can’t see how the opti would only affect only one side.

Just on principal I would check the fuel pressure and maybe use a noid light to check the pulses to the injectors. But more so I would check the sensor in the water pump for an open condition or loose or corroded connection. That will make the engine run rich if not functioning correctly. Also check the coil wire on top of the opti where it comes thru the pump for any arking.

A scanner or a Tech1 might shed some light on the situation by making sure the BLMs are in a good range, O2 voltages are normal, and it is going in to closed loop operation. If you don’t go into closed loop, the O2s don’t come into play.

After all is said and done and you have spend much time checking all items, you might end up back at the opti. The opti has a wide variety of symptoms of failure like stumbling, poor acceleration and such, but usually it will not cause it to run rich, which if true, steers me away from the opti.

 

If you suspect a wire problem, do the test. In the dark or closed garage with lights off, open the hood and start the engine. If you see a sight show (spark gapping), with a flashlight, take a look which wire is the problem and move the wire or change the wire.

 

I had a similar problem on my '92. It turned out to be a bad injector. Ohm your injectors and noid light the circuits to make sure you have power to them.