found a couple of things on 94 4.3

[Joequin]

I found a couple of things on my 4.3 that seemed to change the way it ran.I replaced the cpi,nut kit,cat,plugs,fuel pump and so on and when I first started the truck it ran great but after it got warmed up it started running terrible.I put a fuel guage on it and it read 58 at idle and while off.When I would rev the motor it would drop.It seemed like it was a cpi or nut kit leak so I took the plenum off to investigate this.While taking off the plenum I noticed that the vacuum line on the fitting right at the butterfly wasnt on.This is one of the items that I noticed.So I continued to take the plenum off and I checked the nut kit and cpi for fuel leaks.I turned the key off and on several times and left the key on for a minute or so to see if I could see anything..No leaks at all.While I was there I decided to take another look at the egr.I found that some carbon had got into the egr and was holding the plunger open.I cleaned this when I repacedthe nut kit and blew it out with air after I did the cpi.Somehow it got some more carbon and stuck the plunger.I cleaned it again and blew it out and put it back together and now the truck runs good.I drove it about 30 miles last night and it didnt have any trouble or ses lights.. just a update...

[BlazerLT]

Ah, this is a usual thing on a CPI 4.3L.

If it ain't the CPI or nut kit, more than likely it is the EGR valve.

That vaccum line going from the butterfly is for the PCV valve on the passenger side valve cover. Make sure it is attached to the upper plenum and the L adapter going to the PCV valve.

Have you replaced the fuel filter or PCV valve lately?

[Joequin]

Originally Posted by BlazerLT

Ah, this is a usual thing on a CPI 4.3L.

If it ain't the CPI or nut kit, more than likely it is the EGR valve.

That vaccum line going from the butterfly is for the PCV valve on the passenger side valve cover. Make sure it is attached to the upper plenum and the L adapter going to the PCV valve.

Have you replaced the fuel filter or PCV valve lately?

Fuel filter yes..I replaced it right before the fuel pump change.I thought it might be clogged when the truck first started acting up..I havent changed the pcv valve yet...

[BlazerLT]

I would , it does affect quite a lot on a 4.3L.

Especially idle quality.