Hecubus

I've got a stock 97 LT1 running a 95 OBD 1 wiring and computer. I have had drivability problems with it for a while now and it is finally to the point that I don't know what to do. Sometimes it would run fine and other times it would run rough, lose power and be very hard to drive. It never set any codes. I replaced the ICM and coil and optispark wiring connector but it still had problems. Finally I took it to a shop and they replaced the opti (the one on the car was an AC Delco unit with about 28,000 miles). It ran great for about 150 miles and then lost power and died on me again a couple of weeks ago. I could get the car to start and run really rough at first, but then it just wouldn't start. No codes again. I swapped the ICM thinking that was the problem because the same thing happened to me last year but it still wouldn't start. I took both ICM's to an Autozone for testing and they both passed. I did some testing and determined that the scan tool did not see any rpm from the car while cranking pointing to a bad opti even though it was brand new. In the meantime I took apart my old opti and found it had some oil in it, possibly causing the problems I was experiencing. So I cleaned and reassembled the old AC Delco opti with a new cap and rotor and installed it. This time it would barely start and run really rough at first and then it wouldn't start at all. Set off codes 36 and 42. I swapped the ICM module again just to check and it still won't start but is no longer setting any codes. I am not really sure what to do at this point, maybe there is a bad wire somewhere? Could my ECM be bad? Any suggestions?

ACE1252

With a stock '97 LT1, why are you running an OBDI computer? Was it like that when you bought it?

99 Black Bird T/A

iTrader: (4)

A few random ideas...

How does the MAF look?
Sometimes a dirty MAF can cause all sorts of drive ability issues. See any broken wires? Friend had an LT1 vette that would randomly die. No codes. Ended up being the MAF.

Are all of the plug wires to the Opti correct? Seen a couple of small block Chevy's where someone crossed a plug wire to the distributor and it's happen on LT1's too.

When did the LT1 get a tune up with new spark plugs?

Fuel filter been replaced?

Does Throttle body need a decarbon treatment?

Good luck.

Hecubus

That was the combination of wiring and engine that I had, I thought at the time that the older computer would be easier to work with. I should mention that this was an engine swap, it is in a 77 Impala.

Hecubus

I think the MAF is ok, I have unplugged it while running before and the engine still ran, right now it won't even start. I also double checked the plug wires and they are correct.

SS RRR

iTrader: (2)

Unplug the O2's, drive around until engine is well into operating temp. See what happens.

Hecubus

The car will not start at the moment so driving around in any state is not possible.

ACE1252

10-4 on the engine transplant. This troubleshooting table is from a 1996 manual, but should give you some direction.

http://www.ace1252.com/1996_Z28_Fact...ut_no_run1.JPG
http://www.ace1252.com/1996_Z28_Fact...ut_no_run2.JPG
http://www.ace1252.com/1996_Z28_Fact...ut_no_run3.JPG

A 1995 service manual is here for download. May have a similar chart for the '95 OBDI setup.
http://www.mediafire.com/?40mfgeoe4ctti

Hecubus

Thanks for the link to the manuals. I actually have manuals for a 95 B body and going through that is what led me to believe I had a bad opti. However replacing it did not help.

SS RRR

iTrader: (2)

This doesn't mean jack anymore. What brand was it? The sensor in your old opti is probably bad. The new one could be bad all around. You could open up the new one just to make sure the rotor is tight and opti wheel is not making contact with the optical sensor. Try spraying some fuel into the throttle body while someone turns over the engine to see if it will fire and run. If it does you may want to concentrate your efforts on the fuel delivery system.