1990 Suburban Throttle Body Injection Problem

ACPOWELL0515 · April 19, 2008

It started out running too rich just off idle and finally died. When it will start it runs too rich and dies. I have replaced the coil, the ignition module, rotor and cap and the MAP sensor, but without success. Any ideas about what might be wrong?

98 Z71 SLT · April 19, 2008

One of 2 things happening on your TBI truck

1. Possible leaking fuel injectors. After the engine is shut off, watch the bottom of each injector. If you see any fuel drip AFTER the engine is off, you found your problem.

2. Leaking fuel pressure regulator, which is located inside the TBI unit. Better off getting a repair manual and reading up on the regulator, which I **think** is still servicable.

If both of those items check out ok...you should start looking thru some repair manuals on what would cause your truck to run pig-rich.

need-for-speed · April 20, 2008

I once read a wise (old school ) addage the 99% of carburetor problems are in the distributor. Which means that it's usually ignition related instead of fuel delivery. And over the years, this has proven to be true for me more than once.

However, you seem to have eliminated that.

I hate to advise you based on what was wrong with mine, cuz that's what everyone does - and it has nothing to do with your car. And it's usaully bad advice when people advise you based on what was wrong with their car.

However, I must agree with super stealth. When my wife's '89 Camaro w/ 305 TBI exibited similar symptoms, it was due to the pressure regulator in the TBI unit failing. I suspect that is your problem. However, befor replacing the TBI unit, I would see if it shuts off fuel delivery when turned off. If you remove the air cleaner, you can see the TBI unit flowing fuel while running. Take a look while it's running. Then get someone to shut it off and see if the fuel flow stops. If it does, I would suspect the regulator.

If you need to save money, you might be able to pull the TBI unit off yourself and have someone rebuild it, or buy a rebuilt unit at your local auto parts house.