TBI converision, runnin rich TBI gurus wanted

[76K5]

I've got an 89 YJ I have been working on that has a 350 chevy with a TBI setup. The setup was installed before I bought the jeep. It starts up great, but runs rich as hell, if you putt putt around on the trail for 20 minutes or so it starts to foul plugs, the computer is out of a 87 g-20 chevy van and the motor is 30 over with a small cam, doesnt lope bad or anything, where should I start, I have heard a lower degree thermostat can cause problems, not real familiar with TBI so any help would be great, thanks in advance

 

[76K5]

forgot to mention, does not have a cat, or a dog for that matter

 

[dyeager535]

So first off, assume you've made sure everything ignition related is in order? Cap/rotor in good shape, new/newer plugs/wires (new doesn't really mean anything of course). Then move on to everything else in a good visual inspection: no disconnected wiring connectors? No broken/burnt/shorted wires? Vacuum hoses all in good order? No vacuum leaks? (vacuum leaks at the TBI base are quite common)

Since this is a conversion, was whoever built it smart enough to put in a check engine light? If so, is it lit?

Once you get those taken care of, in order, then you can move on.

 

[1979jimmy350]

Do you have the stock chip in the computer? if you have a cam this could cause an issue like this.

 

[Thunder]

Is it a stock GM TB or a Holley?
Do you have ALL the sensors hooked up?

 

[eagle mark]

What they said.

If your that rich to foul plugs with EFI, you must be in limp home mode. This is a fail safe way for the ECM to run during catastrophic failure.

Error codes?
Vacuum leaks?
Fuel pressure?
ECM # ?
Chip code?
Cam specs @.50 ?
180 degree thermostat