GMC / Chevy TBI Help Needed

[jswainthug]

I have had a problem with my 4.3 TBI recently. The motor did run great for the first few months, but lately it has been bogging when it get up to operating temp anytime it gets into a bind. I had believed it was a vacuum line problem but I replaced all vacuum lines and sensors and still have the problem. I do have 2 lines coming from the intake that I tapped to run my tranny. I don't see why this would cause a problem because it ran so good at first. Any help in this is greatly appreciated!!! I am so frustrsted with this problem it may be up for sale SOON!! Thanks in advance!!!

 

[Tacoma]

Alright..

1. what vehicle is this in?
2. Stock GM harness? If so, are you using the diagnostic port and/or stock idiot lights?
3. Why did you use 2 lines for the tranny? and what tranny?

GENERALLY, and this is only GENERALLY, since there's no other info yet--- but generally, TBI issues can be traced to one of the sensors not working right. But without more info it's gonna be hard to determine what the cause is.

So it warms up, running fine, and bogs when it's warm and "gets into a bind"?? Describe more fully. What do you mean by this?

 

[cjncustoms]

It is in a buggy. Stock harness but cut out what wasn't needed if I remember correctly? I beleive it has a th350 Or th400 behind it with a doubler. There should only be 1 vac hose going to the trans jeff. And that would be located on the pass side of the trans like mine... Where is the other one going? You have checked all the sensors?

 

[jswainthug]

Alright..

1. what vehicle is this in?
2. Stock GM harness? If so, are you using the diagnostic port and/or stock idiot lights?
3. Why did you use 2 lines for the tranny? and what tranny?

GENERALLY, and this is only GENERALLY, since there's no other info yet--- but generally, TBI issues can be traced to one of the sensors not working right. But without more info it's gonna be hard to determine what the cause is.

So it warms up, running fine, and bogs when it's warm and "gets into a bind"?? Describe more fully. What do you mean by this?

Calvin is right it is in a buggy. It is the stock GM harness cut down. There is no stock idiot lights. I am running a TH400. There is only one line going to the tranny. I tapped into one of my lines on the block to run to the tranny. Sorry for the bad description. Hope this makes a little more sense.

 

[ATOYA4U]

I went throught a similar situations. Everytime it was an issue with the fuel pump (not enough pressure)

 

[cjncustoms]

Jeff mine was doing something similar about a year ago. It ran fine cold but as soon as it hit running temp it would cut out and backfire and barely drive. Mine turned out to be plugs and wires and I also cleaned out the egr valve up on the pass side of the block next to the tbi... Might try that stuff first and see if it helps. Worked for me...

 

[Tacoma]

Calvin's on to something. First step is to make sure your tuneup is at least adequate: properly gapped plugs (rare that they aren't, these days, but it happens), no cracked plug wires, distributor and ign. module working right. But your problem doesn't sound like that so much.
A plugged EGR might do that, they are easy to clean: Take it off the manifold, beat the wee out of the pintle. Reinstall. If it runs better, there you go.
After that, start looking at coolant temp sensors, and how's your O2 sensor?

By "I tapped into one of the lines on the block", I assume you mean one of the ones on the intake manifold? There shouldn't be any vacuum lines on the block. You may have bigger problems, if there are.

As frustrated as you are, remember to work through it: if the fuel pump is an issue, it will be an issue under most driving conditions.. if it is a "bogs after warmed up" issue, it's probably a sensor that comes online at whatever temperature. I will look for my manual that lays all that out, it's buried in a pile.

FYI for other people about to cut-down GM harnesses: LEAVE THE DIAGNOSTIC PORTS! they are helpful, and you can read it with a paperclip, seriously. You need a light attached to it so it will blink the codes but the codes are a good place to start, as they are listed 1,000 places online.