Another TBI running rich

[Phillip Perro]

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.

My son has a 95 that did the same thing. His fuel pressure was 12 psi, but it came down to it, and we changed it anyway. Cleared his problem right up.

 

[opus]

This I like but I really dont have that cash to throw into it. If I could figure out what I need and get it used maybe. Tell me what you used for an intake. Did you buy the mechanical TPS kit or.....?

 

[PlayingWithTBI]

I got tired of mine throwing fits and not idling. No codes stored or otherwise. Replaced nearly everything and same problem. My solution was replacing the tbi with a carb and HEI distributor (manifold and all that stuff). At least now I can work on it if need be and don't have to fool with a scanner which I don't know if it would help or not. Much less aggravation and a wider selection of cams for it. Just my $0.02 and my solution.

 

[opus]

Probably so but until you've had this issue for years......

I'm a carb guy. Far more fixable to me.

Timing change did nothing.

 

[opus]

I reset the IAC again. I cannot get the idle to go below 700-725 without my throttle plates sticking. Why cant I drop the idle to infinity?

 

[evilunclegrimace]

I reset the IAC again. I cannot get the idle to go below 700-725 without my throttle plates sticking. Why cant I drop the idle to infinity?

The most likely cause is a vacuum leak some where in the system. If you back the adjusting screw out far enough the Throttle plates will stick, that is just the way things are.

Anotherr thing to look at is the timing if it is not correct it can affect the base idle

 

[opus]

Timing is correct and no vac leaks.

 

[evilunclegrimace]

TPS not set correctly

 

[opus]

Did it according to voltage, but good thought to double check.

 

[Insert Quarter]

You said it's running rich and a number of people think vacuum leak, so by any chance is the valve lash too tight?