4.3 tbi stumped

[guz71]

Trying to help a buddy out with his rig. Hes gone through all the wiring a few times and has checked the timing too. Swapped a 4.3 tbi, tranny, and 208 out of a s10 blazer into his rig and is having trouble with getting it to run right. It starts and idles just fine but if you start giving it throttle and put in under a load (like trying to crawl over something) it starts to fall on its face and it will backfire through the throttle body.

I told him to get his ignition control module tested, it failed and he replaced it with a new one today. He says it runs better but it still backfires under the same condition. I am kind of running out of ideas, my next guess would be the pick up coil but that is a shot in the dark coming from me.

Anyone have any ideas or solutions?

 

[bigblock72]

What is the fuel pressure? sounds like the pressure may be low causing it go lean and backfire.

 

[Cowboy_80]

It's possible that he picked up a new bad ignition module. Has he double checked firing order?

 

[guz71]

interesting about the fuel pressure, but I think it was running rich. Will check it anyways though. Ive seen another buddy that swapped a tbi into his buggy and he had the plugs crossed. It was keeping the timing from advancing and wasnt make squat for power, but it wasnt backfiring like that. Definatelty will check it though. I was kind of thinking about the map sensor.

 

[beto101]

Did you find out what's wrong? I'm having similar problems with my 4.3. Mine starts and turns on and off until it decides to stay on. When I drive it the lights dim varing brightness but work fine at idle. Sometimes can't go over 40 mph

 

[Jason4x4]

plugged exhaust?