Originally Posted by pimpinpetty
i got a 95 camaro z28 lt1 that has been giving me hell forever. Ive tried everything i know and cant figure it out. OK when i start the car it runs fine for about 15 to 45 min depending on weather i run it or just let it idle well when it gets warm it starts to idle really rough almost sound like its missing well after the idle gets really bad the service engine soon light comes on and it runs great while its on it only stays on for maybe 5 10 min then goes off *** soon as it does starts idling ****ty again, backfires when accellerating just runs like poop.
(a few know en problems) now b for i knew that a guy shouldn't i let a friend o mine knock the inside of the catalytic converter out, there is also a 1/2" rubber hose that hooks to the bottom of the stock air intake setup something for emissions i think well on my aftermarket cold air intake theres no place to hook it up and that don't seem right. well thats all i got thanks.
The period where it runs decently is when the computer is reading the engine as cold and requiring "choke" enrichment. When the engine gets to 176 degrees or the timer runs out; it assumes the temp sender is faulty, the computer then leans the mixture out of choke mode. Then based on the data it's not seeing it makes incorrect selctions off the fuel and advance maps.
You just can't knock parts off these OBD I or II engines more so with OBD II. These are completely integrated systems with the computer reading and controlling everything but opening and closing windows. I kid you not, without a ton of technical knowledge about how these systems work and how the computer interprets information and adjusts all engine and transmission operating parameters ---- you cannot touch these things and expect anything to work.
The computer for instance is expecting the catalytic converters to be there and functioning. It's reading, or wants to read, fuel air ratios before after the the converters, monitoring exhaust system back pressure and fuel air ratios among many other aspects. Messing with the converter's guts has affected the difference its expecting between mixture ratios ahead and behind the converters. The hollow converters has messed up the back pressure the computer is expecting to see and probably has also changed the exhaust gas temperatures it's expecting to see. So it can no longer calculate the proper mixture, nor the advance to use and may even have trouble selecting gears if this is an automatic transmission.
The computer can be removed from the loop if you don't have to pass emissions testing. A carb can be put on as well as conventional distributor. Then if an automatic, a separate minimal computer can be bought to run the tranny. But this stuff ain't cheap.
The other way to go is to mod the engine in a way acceptable to the computer, then have it reprogrammed, pre and post processed with OBD II. This isn't cheap either.
The best and least expensive thing, is to return the car to the original configuration, or just scrap it and buy and old pick up.