Just finishing up my swap to TBI from carb on my tow van. I've got most of the kinks worked out, except for a few minor things.

1) Midrange bobble - chugs, sputters, if i put the foot down or let up it'll come out of it. low throttle and full throttle are good. Unhooked EGR valve as recommended and I think it's better, but not completely gone.

2) Low idle RPM - Computer is commanding about a 550-600 rpm idle speed after warm. This computer was out of a 92 yukon 4x4 auto, but am using the trans from the 86 van, so it's not controlling the trans. Could it be that without the input from the trans the computer is not sensing load properly? Any other ideas? Should I just get a chip/burner and start tuning it?

3) Hard Starts - It takes a good amount of cranking before the engine fires. I have to give it part throttle usually to get it to start when cold. (acts like it needs choked). Once it's warm it starts right up. Idle air controller?

Any ideas or suggestions are greatly appreciated

 

Are you using 55 lb injectors at 12-13 lbs fuel pressure? EFI fuel pump?

Q 1 sounds lean.

Low Idle RPM? Need to verify IAC is functional. Witness visual its movement on key on engine off. It will cycle fully. Do a datalog and witness IAC counts cold about 160 and when engine warmed about 5-15 counts.

Q3 sounds like no IAC function. I had to crack throttle when I had IAC failure. Witness visual fuel volume at crank verses at idle. Datalog should show msec on during crank vs the idle msec.

 

Thank you for the response. I went back and checked and found the fuel pump i had was insufficient for the job, so upon upgrading the pump, problems 1,3 were fixed. Hard start was just building pressure slowly, once that was fixed good to go.

It still commands a low idle after warming up, and actually died on me when i was close to home after a good length trip. IAC is working for sure as cold start high idle works. once it's warm is when the low idle is happening.