'90 4.3 running like crap!

[Greenlife1]

Hi guys new here. Had a couple ?'s seeing if you have some insight.

Got the truck about 3 weeks ago. Was running kinda rough, but not to bad. Lack of power...get on the gas, and takes a bit to grab.

So any ways I decide to replace the Cap, Rotor, wires, plugs, IAC valve. Figured that would help some what.
Well I was wrong it runs worse!!
It wants to die when I come to a stop, and runs rougher. Less power. How can this be?

[j cAT]

Originally Posted by Greenlife1

Hi guys new here. Had a couple ?'s seeing if you have some insight.

Got the truck about 3 weeks ago. Was running kinda rough, but not to bad. Lack of power...get on the gas, and takes a bit to grab.

So any ways I decide to replace the Cap, Rotor, wires, plugs, IAC valve. Figured that would help some what.
Well I was wrong it runs worse!!
It wants to die when I come to a stop, and runs rougher. Less power. How can this be?

the IAC could be defective put old one back in ....you do not move the motor controlled valve as this will break the gears....

when doing plug wires you must use a meter to measure the ohms before install not after it runs like crap....all should be the same approx...

engines this old need new vacuum lines ...with a vacuum guage make sure there are no leaks ...or collapsed lines ...

routing the plug wires you will need tyraps plastic ties to secure the plug wires as the original holders are most likely destroyed ...

[Greenlife1]

Thanks for the help. Check and replaced the vacuum lines...even though they were not shot. I pulled some codes. 13, 43, 54. So I replaced the Fuel pump relay, and Electronic Spark control piece. I tried , but couldn't get the O2 out. That solved the problem.
I did replace the wire holders.
It runs the way it used to. But the main reason i changed all this was so it would run the way it is suppose to.
It only has 76,000 on motor. 225,000 on body.
What would be the next things to look at to replace?

[j cAT]

with the engine hot loosen the O2 sensor ,,,then wait for exhaust to cool down to replace ...

[Greenlife1]

Well after a full inspection of the exshust I see that it all needs to be replaced from the exshust manifold back. So I figured if I am going to do that I mise well put headers on it. Should I skip puttin the cats on it? There is no emissons testing by me.
Also wondering what your thoughts on this would be.....
I will try to describe it as best as possible....
I am hearing a whinning noise that seems to be coming from behind the cab. Like where the drive shaft meets the tranny. It is worse when I give it gas, but you can still hear it till I stop. It sounds like.....gears rubbing?? I no its not, but what do you think it is? Maybe U-joints?

[mechanic1980]

You should pull the harness for the fuel spider and ohm the legs out they are probably shot chevy redesigned the poppit valves for that motor. if the spider is bad it will always ru rough unless replaced cleaning doesnt help

[j cAT]

Originally Posted by Greenlife1

Well after a full inspection of the exshust I see that it all needs to be replaced from the exshust manifold back. So I figured if I am going to do that I mise well put headers on it. Should I skip puttin the cats on it? There is no emissons testing by me.
Also wondering what your thoughts on this would be.....
I will try to describe it as best as possible....
I am hearing a whinning noise that seems to be coming from behind the cab. Like where the drive shaft meets the tranny. It is worse when I give it gas, but you can still hear it till I stop. It sounds like.....gears rubbing?? I no its not, but what do you think it is? Maybe U-joints?

could be the hub bearings ..lift vehicle and rotate the front tires should rotate smoothly no ruffness/vibs...

U joints will clunk or squeek..with the vehicle in neutral rotate the axles and check for play / looseness..

with something this old bushings /axle sleeves may have wear ..

[tblake]

Originally Posted by mechanic1980

You should pull the harness for the fuel spider and ohm the legs out they are probably shot chevy redesigned the poppit valves for that motor. if the spider is bad it will always ru rough unless replaced cleaning doesnt help

In 1990, did they have poppet nozzle's or were they TBI?

[93LT]

Originally Posted by tblake

In 1990, did they have poppet nozzle's or were they TBI?

Should be TBI. Since it is in the C/K forum, the full size trucks didn't receive the Vortec V-6 like the S series did in 1992. I'm thinking the full size trucks utilized TBI on the 4.3 through 1995.

[Greenlife1]

Yes TBI.
Also The noise was coming from rearend.
Threw a bearing! Rear end is shot. Where the race sits on one side it has a slight cup shape, thats not good.
Also imput shaft is pretty sharp, and beat up.

So now what to do?
Should I replace the whole rearend? I can get one from a guy not far from me that is all asembled...axle, drum assembly, leaf springs for $300, but who knows what kind of shape it is in.

Or they is a guy selling a 97 Chevy S10 with a blown motor(4.3).
I need to go look at it, but from pics it looks nice. $500 for it.

What do you guys think I figure for 200 more I could just swap out my motor and put it in the s10 right?

[Greenlife1]

Well I tried to get the S10, but he sold it already.
So I need to get the rearend.
Also I need to replace both motor mounts as the are shot.
Planning on putting headers on since the one mainfold has a crack in it. Anybody recommend where I can get a pair a a decent price?