Please someone, I need help. I have a 91 Z28 5.7L TPI Auto. The car is running terrible, I have posted issues before and recieved responses and suggestions but nothing seems to help. The car has very poor idle quality, and runs hot. I keep getting ESC module codes, lean codes. I have changed the O2 sensor, knock sensor, ECM, prom, IAC, TPS, coils, cap rotor, plugs, wires, reset ignition timing to specs, and injectors. The car doesn't have a cat, or air pump. It has headers with 3 inch exhaust. The car stalls alot, and if its over 70 degrees outside it runs well over 220+ degrees. All cooling system components have been changed except for the heater core. The dtc's don't stay in the ecm ( the check engine light comes on and goes off at random times). Today I was screwing around with it and I pulled the number 3 spark plug wire off and the idle quality got better( no misfire), but off idle it obviously misses, same thing happens if I remove the harness connector for cyl#3 injector. I really don't know where to start because it seems like it just keeps developing more problems. Has anyone experienced similar problems? Also if it makes any difference the car seems to run slightly better when its raining if that makes any sense.

 

Since you've done most everything else....

Have you done a compression and leakdown test? Also run it with a vac gauge hooked up a look for flutter.

It SOUNDS like you've got something related to that one cylinder.

You could also possibly have collapsing lifter(s).

 

Thanks for the ideas, but I now think I know the cause of the issues. I believe there is an issue with the PROM programing. I think I may have made too many mods without making proper programing adjustments. Fuel map, timing curve, etc.

 

What mods have you done? The car will still run with well even with significant modifications. I would check the fuel pressure and simple things, make sure all of the ignition wires are going to the right cylinder (this mistake gave me a hell of a time.)

 

So far its a 40 over 350, 24 lb injectors, no cat, no AIR pump, headers, 3" exhaust, 160 stat, hypertech fan switch. Im currently running an ECM and prom from a 90 Iroc 5.7 tpi. I have the fuel pressure set to 43.5 psi, tps volts are at .54, MAP volts are good. I cannot find any vac leaks, but I can seem to get the idle right plus it stalls all the time, and it runs hot. The ignition timing is dead on, but Im constantly getting code 43 (ESC), and lean codes. I don't know any specs on the cam, but I do know that the heads are not the correct heads for a 5.7 tpi. I do have the correct heads and plan on installing them. Recently I drove the car for a while with my scanner hooked up and the car never went into closed loop, its always in open loop. Any ideas?

 

I had a similar problem with my '90 Vette, where I was getting a code 43 and the idle was terrible. Changing the knock sensor took care of everything. I would also ohm the injectors when they are cold and again with engine warmed up, (I had a new ford injector die in less than a year.) My understanding is that running 24lb injectors requires a custom prom, this, along with an aggressive cam may be more than the computer can handle.

 

I definetly plan on doing all that again, but Im thinking that the injectors are too big for the factory fuel mapping, and that there is programming issues.