I have a 88 LB9 5.0 IROC with a T5 transmission.
My issue is when the car is cold it runs good, but as soon as it starts to warm up, it loses power and stalls above 3000 rpm's.
I have replaced the MAF sensor, the catalytic converter, the ICM, coil and pick up coil, cap and rotor, plugs, fuel pump and fuel filter, the CTS, The EGR, the fuel pressure regulator, the fuel relay and the other 2 relays beside it. I forget their names right now. I am at a loss and do not know where to look next.
This a project car that sat for 14 years before I got it from a friend.
Any advice would be appreciated.

 

Do a hot and cold resistance check on the injectors with your ohm meter.
There is a high likelihood you have bad injector(s), especially if they are original, or replacements of the original Multech style.
My car will start right up and run magnificent until it gets warm. Then it runs really bad. I did a test on my injectors, and once they get hot, I have 4 that are bad.

 

I done the check when it was cold and they tested fine, but I will try the hot test and see if the results change. Thanks for the reply.

 

I checked them again cold got 16.8oms and got the same reading hot. I drove it until it started to act up again and pulled in the driveway and did the check . The cold start injector was 4.5oms. Does need to be the same as the others? I would think it does, but I'm not sure. I read in a different post that the distributor would cause it to act this way too. Thoughts?

 

Ok, I am still at a loss with this car. I have removed the new Cat and straight piped it. no change so, I will be putting it back on. I replaced the O2 sensor. I swapped out the fuel relays again. no change. I read somewhere that the CTS could cause these symptoms. I replaced it but I think I teflon taped the threads. I will pull it apart this weekend and clean it up and put on new 8m spark plug wires. I am running out of things to try. FYI, I am not getting any codes either. I have already replaced all the stuff that pulled codes.
Could the fact that I changed the gears in the rear end affect the ECM? I went from 3.24 to 3.73's.

 

Well, it appears to have been my fuel pump. It was only a couple of months old. Weird. Unfortunately, I did not figure it out until I replaced the injectors and spark plug wires. Then I went back to square one and started over. New Fuel pump and fuel filter. Pressure checked the fuel lines and fired it up. Ran great with the exception of when it was cold it would not stay running by its own. Once warm it was fine. I think I'm finally seeing the light at the end of the tunnel. I reset the timing to 6btdc. Tomorrow, I will pull the valve body off and clean it and the IAC. The tps is new so I will check it when I put it back together. I want to thank third gen Web site for showing what other members have done with similar issues. I just wish I would of got more response on this post, it would have saved me a lot of searching, guessing and buying unnecessary parts. I just hope i can get it past this California smog test. They are killing me.

 

What brand fuel pump did you put in there?

 

your ICM could be going away. its common. just be sure to NOT buy anything from china. mine is a BWD from oreilleys. theyre good to go.

 

It was an airtec from Autozone. I am so done with Autozone. I went through 3 different MAF senser from them too. The store is so close to home and convenient.

 

My ICM is new from OREILLY and is also a BWD. So far the parts from this store have been working good unlike Autozone. I have replaced just about everything I can think of. Partial list is in my first post, less fuel injectors Bosch 22lb, O2 senser and MSD red 8.5 sparkplug wires. Now, I just need to dial it all in I hope? I dying to start driving this car.
I got over 2K invested and still haven't got it registered. It failed my first go around with smog. This TPI has been a learning experience.

 

auto zone sells the absolute CHEAPEST Chinese crap they can get. all about the share holders, fu$# us parts buyers. airtec,cardone. GARBAGE!!! I buy what I need from oreilleys. and so far ,so good. I bought SEVEN re-man MAFs from auto zone before I kicked them to the curb. bought a NEW one from "rich porter" and all is well. and let me tell you something good,,,,, call your local GM dealer and get the correct part #s from them regarding the MAF relays, that way youre sure to cross them over to the correct ones. I have a 86 TPI and after the learning curve. I have a sweet running car... pay attention, and good luck

 

It funny that you mentioned the local GM dealer. They were the only place where I could find all 3 relays together, so I bought them. It costs me more, but I got the right parts. I read on one of the forums that there was 2 different types and none of the parts stores knew what I was talking about. The GM guy pulled all 3 up and I bought them.
It seems like we all have some what of a learning curve. I am just hoping I can get the same results as you did and have a sweet running car in the end. That would make it all worth while.

 

with these cars, you gotta be serious. OR fn crazy. I haven't decided which yet. the biggest problem IMHO is junk cheap *** MAFs and in correct relays. once you get past all the cheap crap .and you get a NEW MAF and the correct relays, it gets a LOT easier to make them run. congrats, and keep at it!