I just completed my 454 swap into my 1989 K2500 and am having some issues im trying to rule out.

When wiring the TPS and IAC i just matched the colors of the wires up, but A,B, and C did not correspond between the 2 harnesses. Did i connect any of the wrong? What wires (ABC) should do what?

BTW its a 1989 Chevy 4x4 2500, had a 350. 454 engine from a 1993 K3500. using my 7747 with a chip from Brian set up for a 454. Re-used the CTS, MAP, dizzy, EGR, from the 350. Used TPS and IAC from 454.

The problem that im having is a erratic idle, hunts up and down, and a cut out when I blip the throttle from an idle. My initial thoughts were vaccum leak, but a quick test said probably not, but i do need to do a more thorough test. Timing is set to 4*BTDC.

 

i have found on pirate 4x4 this quote

"if the wiring harness is from a 350 then the wires on the TPS need to be switched. The dark blue and gray ones."

anyone confirm? would this cause my hesitation/stumble

 

I posted my successful wiring of IAC from 350 harness to 1995 7.4L TBI unit with IAC in this thread.

https://www.thirdgen.org/forums/diy-...i-iac-7-a.html

 

i did some checking tonight and the gray wire is 5volts ref, and the blue/white wire is .5 to 4.5 volts, transitions smooth. so i guess that rules out TPS from my problems. I suppose my next step is to check fuel pressure, vacuum leaks, and so on. Any hints on where to look? Any help is appreciated.

There is a thought in the back of my mind that perhaps the chip is at fault, but ill give brian the benefit of the doubt and check everything else first.

 

A good chip the CE or SES, key on engine off, will blink and stay on. A bad chip or .bin with blink rapidly on same. you do have the CE light right?