DALOS43

Hi just wanted to to see if I could get some help on my 93 Z28. It recently started backfiring and losing power at the same time. Its only happens once ive been driving it for awhile. Whenever I let it cool down it goes back to driving normal. Can anybody help me and see what the problem might be? thanks

Mharvey33

How many miles?

DALOS43

Its has 130,000 miles. Replaced the optispark 2 years ago along with wires and plugs. Was doing the same thing the last time I replaced it. Not sure if its the same thing happening again?

Injuneer

Have you checked for codes? Have you checked the fuel pressure? What brand is the replacement Opti? Did you loc-tite the rotor screws before installing Opti? Have you had the ignition control module tested, making sure the ICM is hot while being tested?

DALOS43

its recently happened havent check the fuel pressure or ingnition module. The opti that I had change 2 yrs ago was a new cardone Advance Auto Parts opti with lifetime warranty
Yes check the codes. its showing :
-26 quad driver module 1 malfunction
-36 high resolution pulse circuit
-55 fuel lean malfunction
-61 air conditioning system performance

Injuneer

DTC 36 is for the high resolution cam position signal from the optical module in the distributor. The code indicates the signal is missing. The engine will continue to run without the high resolution signal, by relying on the low resolution signal only. The only affect should be a minor increase in spark scatter, not enough to cause the problems you are experiencing.

However the code does indicate that at some point the signal is being lost. That does raise the possibility that the signal is intermittent, and possibly corrupt, which would cause the problems you are having. The problem may be the result of heat soak of the optical module.

For starters, check the Opti harness connector for being loose (broken retainer clip?), corroded or having a bent pin. Some of the newer Optis have an integral harness on the Opti, which does away with the connector at the Opti, but still requires the connector to the stock harness on the bracket on the passenger side of the intake manifold. Don't know if the Cardone has the integral harness, or not. In any case, check that connector as well.

Fatdog2

Air pump?.This thing keeps the extra gas from keep pumping during letting the foot off the gas.When you take your foot off the gas ,the injectors are still pumping.Hench, the air pump.A neutralizer.Call me crazy,Idunno.

Injuneer

Injectors do not continue to inject fuel on closed throttle decel. First the PCM reduces the pulse width to cut fuel, and then if the decel continues there is a "decel fuel cutoff" (DFCO) in the program that cuts fuel to the injectors completely on closed throttle, and keeps them turned off until the engine reaches a fairly low RPM. You can feel the fuel cut back in if you watch for it. The AIR pump is not used for that purpose that I am aware of.