89 Silverado 350 misfire
 

Hey guys I have a weird misfire I'm getting, I recently put new heads, plugs, wires, oil pan gasket, oil filter housing o rings, belt tensioner. I retimed the dizzy after I finished putting in the new heads.

When I was cleaning parts when I removed the heads(keep in mind they were filled with sludge) and the intake had a lot of carbon build up. The wholes going to the egr on the intake were completely plugged so I cleaned it up, I never removed or replaced the egr valve. So I'm thinking this is my problem. Once the truck warms up and I slightly give it gas it misfires. (ONLY WHEN WARMED UP) it also does it at a stop when your trying to go.

HERES A VIDEO OF A BETTER EXPLANATION. http://youtu.be/OU6J-dWvRdI

Re: 89 Silverado 350 misfire
 

I know my 94 is all original, but occasionally has a miss/stutter but doesn't interfere like yours seems too. I know on my 94 there is some sorta wire that has to be disconnected to do the timing, does yours require the same thing to proper set the timing. I Kinda am thinking also the EGR, but I a, a backyard find it by luck mechanic. Hopefully one of the more techy guys will be able to help ya.

Re: 89 Silverado 350 misfire
 

My sububan would almost stall on start up from a stop and it was the EGR. But it never did it when it wasn't under a load. So it might be two issues. BUT, if you replace the EGR BUY A GM! Don't waste your money on aftermarket. I didn't read that till after I put one it and it I ended up with a new DELCO EGR to fix the issue.

Re: 89 Silverado 350 misfire
 

Some of the TBI egr's are ***** to get right. There are positive and negative back pressure units and supposedly they aren't easy to tell apart.

I suggest you try blocking it off to remove it from the "misfire" equation before buying parts.

Re: 89 Silverado 350 misfire
 

Check the wiring harness. I had fought mine for weeks and come to find out I had 3 broken wires in the main harness.

Re: 89 Silverado 350 misfire
 

Thanks for the replies guys, I just took out the egr valve. And I don't have a vacuum guage, but it's the same concept. I pressed down on the valve and I put my finger to cover the vacuum port and the valve closed. If I'm right it should hold the valve until I release my finger. The vacuum line that goes to the egr solenoid is it suppose to be on the top nipple or bottom?

I'm sure it's a bad egr valve, so I will be putting in a new one. Would a ac delco be good? I have heard bad stuff about aftermarket ones.

Re: 89 Silverado 350 misfire
 

That is exactly what mine was doing. I could plug the vacuum line but it would still hesitate. I went with an AC Delco second time around and it solved my problem.