Need some assistance troubleshooting and fixing this problem.

I replaced the coil 18 months ago, Opti, water pump, wires, plugs about 6 months ago. Replaced the MAP and fuel pump just a few days ago.

When cold car runs great, no stumbles all the way to red line.

Long drive, stop at rest area for 10 min, start and it runs like crap bucking, almost shutting off for a few minutes until I get up to highway speed.

High spirited driving (road course) 20 minute sessions. First session of the day is great, car is cool, come off the track water is about 205, oil about 180. If the next session is before the car cools completely as soon as it gets to high temp (less than 210 digital water and about 200 oil) she starts bucking and stuttering.
Red flag drill, sits at idle for 5 min and runs like crap until you get to the pits, shut her down and let it cool off.

Lets talk about codes - there are none!!!!

So any ideas on what I can test?
Troubleshooting ideas?
Treat it as an electrical problem? Cooling problem?

Thanks in advance for your ideas

 

Possibly a bad Ignition Control Module (ICM)?

 

Doesn't sound like electrical, nor cooling. It does sound like possilbly injectors leaking down into the cylinders. You getting smoke with the start up and bucking?

 

Not noticible, but there is a strong smell like its running rich.

OK, I'll ohm out the injectors cold and hot. I know thats one way to look at the injector health. Any other ideas on checking injector health?

 

Could be a bad EGR valve or possible bad AIR pump. I've had both go sour and do exactly has you describe. I'd lean towards the EGR valve though.

 

Should have included the EGR valve and selenoid in the list of parts replaced with the Opti. I'll put a vaccum on it and make sure it still moves.

 

Put a pressure gauge on the fuel rail and check for leak down after the engine is shut off. I am thinking you have an injector leaking gas into a cylinder after shutdown. That would cause the rough running on start up, etc.

 

[QUOTE=jaa1992;1561480131]Need some assistance troubleshooting and fixing this problem.

I replaced the coil 18 months ago, Opti, water pump, wires, plugs about 6 months ago. Replaced the MAP and fuel pump just a few days ago.

When cold car runs great, no stumbles all the way to red line.

Long drive, stop at rest area for 10 min, start and it runs like crap bucking, almost shutting off for a few minutes until I get up to highway speed.

High spirited driving (road course) 20 minute sessions. First session of the day is great, car is cool, come off the track water is about 205, oil about 180. If the next session is before the car cools completely as soon as it gets to high temp (less than 210 digital water and about 200 oil) she starts bucking and stuttering.
Red flag drill, sits at idle for 5 min and runs like crap until you get to the pits, shut her down and let it cool off.

Lets talk about codes - there are none!!!!

My 93 had the same problem. Ran great when cold, plenty of power for the first 10 minutes or about 6 miles, after that it would stumble/buckle like you described. I replaced the Opti,wires, plugs, fuel filter, I also check the fuel pressure at the rail both cold and after the car warmed up and started to stumble. I checked the fuel injectors when the engine was cold as well as when it stumbled. I cold not find the problem. I took the car to a Chevy dealer, paid the $70 to have the engine on a scanner. The mechanic got the car to act up but could not pin point the problem (also no codes). While the mechanic had the car acting up in the shop he checked all of the connections to the sensors/ computers and the problem disappeared. He thought the problem was maybe a bad connection but was not sure. That was last spring and about 2,000 miles ago with no reoccurrence.