Greetings All,

The story of my LT1 continues Two months ago or so I was having hesitation/starting problems. All with no codes! As suggested I replaced the Opti and it all seemed fine (somewhat my fans were not coming on, so I replaced the temperature sensor in the block and waterpump and it seemed better, although I think it was running warmer then before but I summed that up to anomalies in sensor manufacturing. Anyways, this afternoon, got in, and it runs rough in idle and hesitates when I try to drive and it will just never go. Still no trouble code!! This is what I have replaced recently:
Optispark (~2 months)
fuel filter (~1 month)
fuel pump (6 months)
spark plugs/wires (3 years about 30K) They look really good still and were the expensive kind.

I have checked so far: TPS which is ok. MAF which is ok

Any thoughts! When I had the previous problem I finally took it to the dealer and they could not tell me anything either except possible the optispark and $200 for that help. I have been thinking about buying some diagnostic software where I can read more then a simple OBDII code reader. Any suggestions? Thanks in advance!

 

What brand opti replacement did you use? Did you test the coil and the ICM? Just cause a wire looks good, doesn't mean it is.

 

I have not tested the ICM or coil. Any articles/how-to?

 

im not sure if this would have anything to do with it but the iat?

 

Not sure about the iat either, anyone? I did just check the coil to modified instructions from shbox since mine is a 96. I have a three wire connector to the coil and all read about 5780 ohm which according to other threads sounds to be ok. I also check the the connector to the ICM with the coil connected and I have 12 volt on the pink(that is what it looks like) and green wires, which are the outer two. The inner two are black and white and have 0 volt. Anyone??? Help would be sooo appreciated right

 

Ok, so I just checked the IAT and its reading fine in both voltage and ohms. The single lead water temperature sensor in the head is reading a little high which is reflected on the meter in the dash but that seems ok. I have not checked the water pump temp sensor yet. Next plugs and wires?

 

http://shbox.com/1/4th_gen_tech2.html#opti_test
The connector terminals are labled with small letters. You should have >10v dc on terminals A and D to ground (outer wires). You should have 1-4v ac on terminal B to ground and continuity from terminal C to ground.

 

Disconnect both battery terminals and clean both cable ends and the
battery terminals. And you might want to (just to eliminate the
possibility) remove the plugs, inspect, and clean them; and also,
check the ohms for each of the plug wires. You might also want to
check the ground straps.

I had a similar problem where the car ran like cr@p and also, the tranny
was not shifting out of first gear. It was suggested to me to clean the
battery terminals, which sounded ludicrous, but I figured, what the heck,
I'll try anything (plus it's so simple to do). I cleaned the terminals and,
voila!, the car ran perfectly and shifted as normal. Not saying this is
your problem, but it's worth a try.

If nothing else, you'll know you have clean battery terminals/wires and
that the plug wires and plugs are in good shape. It really is a process
of elimination for most troubleshooting. Always start with the easy stuff.

 

Thanks for all the tips. SS.slp.ls1, in reference to the diagram from shbox, I am a little confused to what connecters he is referring. I do not have any letter on the ICM connector, I have not checked the connector coming from the opti but will do that today. Plus the wire colors he is referring to pink/black/pink-black/white/white-black are different on mine they are pink/black/white/green.

Caldercay, the battery is actually a good idea and doing it now. As far as the resistance on the spark plug wire, what should they be?

 

I would look again, it should be labeled on the connector. You could always use process of elimination: connect your volt meter to one of the middle terminals and ground and measure the ac voltage while cranking, then do it to the other middle one. One of them should be 1-4v ac. Then test the other terminal for continuity. If neither read 1-4v ac while cranking, then it might indicate a bad opti or opti harness.

 

SS.slp.ls1, just to make sure I understand what you are saying, are you referring to the connector that goes into the opti itself or the connecter that is connected to the ICM? I know this probably sounds obvious but I want to make sure.

 

You should be performing the opti and spark test on the pigtail that connects to the ICM.

 

Well I checked the voltages again on the ICM connector. I am by myself so I can not check the cranking ac voltage of course. In reference to the shbox diagram however, I am getting totally opposite, the outer two wires (green/pink) give me 11 volts. Both inner wires(black/white) give no voltage and about 100 ohms to ground). Anyone else have these colored wires/connector?

 

My mistake, I really really cleaned the connecter and the numbers are actually on there but really faint, I guess the mold is wearing out at GM . Anyways, I am getting 11 volt on A and D as I am supposed to, I guess I will have to wait till I get help to test for the B wire and ac voltage during cranking. Any other thoughts?

 

There is no way for you to prop up the volt meter to be visible through the window? I would get a buddy to help read if you can't. The 1-4v ac from terminal B to ground is your low res opti signals. You need to verify those signals.