Swapped 5.7 TBI in my truck, need help.

[Branwhy]

I have taken the 4.3 TBI out of my 88 c1500 and put a 5.7 TBI in it. I used the 4.3 wiring harness, and swapped computers (not sure if I had to), anyways long story short, three truck starts and runs, but runs sluggish. Upon light acceleration it sputters bad until the rpms get up a bit then it takes the fuel good. When the truck warms up and you try to start it, for about 5 seconds it runs so crappy it's almost stalling, then after the 5 seconds (ish) it picks idle up and idles (not too bad but not quite 100). After checking the egr valve it works, no vacuum leaks that I could find. there are 3 plug ins on the wiring harness on up by my intake manifold but I can't find anywhere they plug in, and the sensor in the driver side exhaust manifold isn't hooked up (head is broken). I don't really know what to do, and dont wanna give up on my old truck but I am completely stumped, help !

 

[kennythewelder]

You are having ECM- or sensor issues. You need to do a live time sensor reading so that you can see what sensors are working properly, and what ones are not. I have a Jet programmer for my truck that has this option. My truck is a 97 so it is a Vortec, with OBDII system where yours is OBDI. I am not sure how to do a reading on yours, but I know it can be done. Also a code reading could help to pin point your issues.

 

[MXR597]

You are having ECM- or sensor issues. You need to do a live time sensor reading so that you can see what sensors are working properly, and what ones are not. I have a Jet programmer for my truck that has this option. My truck is a 97 so it is a Vortec, with OBDII system where yours is OBDI. I am not sure how to do a reading on yours, but I know it can be done. Also a code reading could help to pin point your issues.

To read sensors on a TBI you need to get a cable and TunerPro RT

Cable: http://www.aldlcable.com/
TunerPro RT starter guide: http://www.gearhead-efi.com/Fuel-In...arter-Tutorial!-New-users-this-is-a-must-read

Other than that I can't help much cause I don't know much about doing swaps, best of luck to you!

 

[skylark]

The sensor in the drivers side exhaust manifold is the o2 sensor. It will run like crap until you get that fixed.