I have a 2000 chevrolet silverado 4.3 v6 and it missfires untill it warms up,i have replaced the battery, tps, mass air flow sensor, and the plugs, wires, distributer cap, rotor button, and the fuel pump has less than 10,000 miles on them.Any idea.

Is the check engine light coming on?, And how long has it been since last tune-up? Most of the time a mis is cause by bad plugs/wires/coil pack, also a bad valve but a basic tune-up would render the problem

I believe your problem may be fuel injector related...
They have a problem with sticking closed or open after sitting overnight due to deposits that build up on the injector poppet valve ball or seat...
Also on some models the fuel tank fill pipe assy has compounds that the fuel extracts and deposits on the injectors as well...
Gm does have a good cleaning process for the injectors and there is a revised fuel tank fill pipe assy also ...again depending on your model....based on the VIN break point,for the fill pipe procedure..
In any case ,your injectors are probably the culprit...
But check into it with Gm...because if related to the fill pipe as well...then the problem will keep reoccuring if not replaced..

Jeez...I hope that made sense...it did to me but I'm old...

Let me know...

Jim

Yes, the check engine light is on. I had it read and there were no codes given, just said mostly misfire cylinder 4 but some cylinder 3.

In Reply To

It will idle fine and you can put it in neutral and rev it up fine.

http://www.autozone.com/.../repairInfoPages.htm this gives a little info, I would start with a simple tune-up before doing anything else, thats if it haven't had one in the last 2years but a misfire code usually is a coil/wires or plugs pretty much of the time.

BTW, if the tune-up don't get it, don't be in haste to overlook Jim's anwser,this guy has an average of 99.99% of hitting the problem on the nose

Damn...

Did I drop down to that low????


(This post was edited by JIM N on Mar 8, 2008, 3:30 PM)