Working on a 3 yr problem that no one can figure out.
1993 5.7 TBI. Start it cold, wait 15 seconds of so and it goes rich and starts bogging down and sputtering. Hold the throttle down for 30 seconds then it gets past that issue and is good to go. This of course depends on the temp. When its cold, like 0, it takes longer to reach the rich stage, but its like clock work.
I'm trying to keep this simple for you, for now. I've replaced everything, at least once. Give me some ideas. Dont spend a lot of time though because I've probably already done it. If by chance I havent, then we can go into detail.
I bought a bunch of tbi stuff from a guy who was going out of business.
Got it all dirt cheap and threw it on cuz why not?
Ended up with the same damn problem and its all NOS GM delco delphi
Deffinetly temperature related.
First thing, set your timing back to 0 tdc with the engine warm and the dist reference wire diconnected.
A stock GM TBI will never work right unless its at 0
When you get timing set and reconnected.
Run it for a while before you reset the idle air control.
It will run like crap but thats part on the relearn.
Make sure the pintle on the IAC is pushed in before you screw it back in.
You didnt mention if youve rebuilt the throttle body.
The passage behind the IAC gets plugged full of carbon and so does the EGR system.
Look for throttle shaft wear on the linkage side of the TBI. Really common problem. Try to wiggle it around. it shouldnt move.
A worn throttle shaft is a vacuum leak.
I spent about a week and 60 bucks on beer trying to find the "one thing" that caused the problem.
Turns out, it was about ten things that added up beyond what the computer could compensate for.
You already spent the money brother, Maybe all you need now is the beer.
Good Luck, hope it helps
