Hello, Another time here, I'm spanish and write in English is very hard to me, now I have a crazy problem with a 90 iroc-z and don't know very well how I can explain here. Well, this car has a rebuilt 305 TPI about 1500 milles ago, but never run fine. The engine anytimes crank and run very fine, but only for about a minutes, them become to stumble (? don't know if this is the correct word) like if 1 o 2 cylinders fail. Now near allways crank and run with this fail, bad iddle, and anytimes stall. But now at least I have a error code 42. This sound fine but......... I have an old distributor with a broken magnet off of my 91 trans am., and become to change the parts like the electronic spark module (nothing chage), then the pickup coil (nothing), rotor, cup, nothing. no change. After that, I check for continuity (and ground) the four wires of the electronic spark module. This is right, 0 resistance, and not groung. As the fail continue, I put the complete distributor of the 91 trans am (I know it is good and running), but no changes. At this point I suspect of the ecm. As I don't know where the problem is, and if there are any wire short, or grounded in the camaro, and I don't want to possibly burn the TA ecm, I put the Camaro ECM in my TA, surprise!!, run very well, perhaps better than the TA ECM . Anyone have an idea of where I can continue looking for? Bad wires?? with the polymeter I see continuity, and not ground, Any very little short or intermitent cut to ground? How can I find it? Could a defective spark wires promote a 42 error code? All replys or opinions are wellcome. Thanks.

New updates:
I put a new spark wires without any advance, problem persist.
Then, thinking in any ocasional short or ground, with the ecm pins, and other connector off of a donor V6 of a friend, I made a new wiring arness for the EST, but nothing change....... I am desperate

I am thinking all things that not work:
-Put complete distributor of a fine runing car
-Put the ecm of this car in the other car, and run fine.
-Put new spark wires
-Put the coil of the other good running car
-Made a paralel wiring arness to the EST looking for a short or ground

Nothing of that make any change in the engine run, and allways persist error code 42, anytimes in only a seconds after start, other a few minutes after.

I attempt to see what more sensors, or things can cause a 42 code, but I can't.

Any idea on where can I continue looking for?

This thread has more ideas of things to check, but doesn't appear to have a final solution:

http://www.thirdgen.org/techboard/el...e-42-some.html (Error code 42, and some tach questions.)

I had seen it before open this one, and a lot more threads about this error code, but anything help. Most of them don't say the final solution, or don't have same symtoms as mine.

Now my main objetive it to know what more things, sensors, or what is, can cause this failure and this error code. Perhaps this could be a question to the DFI secction??

http://www.troublecodes.net/articles...ndrstd42.shtml
http://www.megamanual.com/ms2/GM_7pinHEI.htm

Fran , ¿ comrprobaste el modulo de control de HEI ? , esta bajo la tapa del distribuidor.

Fran , have you checked the HEI control module ? , it's under the distributor cap.

Luego el lado de la ECM :
Then the ECM side :

chevythunder.com :

1990-92 speed density f-body (ecm#1227730) (Camaro/Firebird):

http://chevythunder.com/fuel%20injection%20ecm%20pinouts.htm#1990-92%20speed%20density%20f-body%20(ecm#1227730)

Si, puse otro modulo que tengo de repuesto, incluso el distribuidor completo de otro coche (el mio de diario), y nada.

Yes, I put another spare modul, and other complete dizzy from a running car..... nothing.

In ecm side I check for volts with a digital voltmeter, and just started the engine all are right, but in a minute or so, in #C8 pin, volt became to drop from the right 1,3 V to a jumping 0,6-1,5, here is when I ear the engine failing, like if only 6 or 7 cylinders was running.

This was the same with the other dizzy too, so I know that the EST is good.

any idea?