Weird idle / misfire

i dont know whats up itll be fine then if i rev it it like i have one of the big blocks with the hit and mis sound but then it goese away and if i just let it sit and idle its does it then evens out again. i dont know if the cpi and nut kit were ever replaced but if that went bad wouldnt i just not start? or stall i have no problems but really bad 4mpg...

Check Wire and Spark Plugs And Timing Belt.

@ 4 MPG I would say you are leaking gas into plenum or maybe a bad injector. Even a badly tuned 4.3 would get 10-12 mpg. Maybe one of the injectors stuck open. Smell your oil and see if it has a gas smell. You can do other things, ie. plugs, cap, rotor button, filters, wires, but.... 4 mpg raises a major flag. And no, a bad CPI/Nut kit would not keep truck from starting unless it was not letting enough fuel pressure build. The regulator going bad could do it, but, leaking gas line or injector would only cause misfire, poor fuel economy, possible engine failure(gas in oil). Plenty on information here posted by far more knowledgable folks than me on this. Pull off your vortec plate, remove the large round assy. and look into the plenum. Check the oil for a gas smell. I am assuming you have a CPI motor (vin W) and not a TBI motor.

cpi motor... i just did all the plugs filters radiator flush changed oil to synthetic 2 days ago im sur how the gas milage is tho.... im doing cap rotor and wires today

I hate to sound like a dink, but are you sure you're calculating it correct? Given where your truck SHOULD be I have a hard time believing that it would run in that poor of shape, let alone without some kind of indication as to what's wrong.

Pull the IMTV today and look. It won't even take 5 minutes.

It really sounds like your CPI and nut kit needs to be replaced. Pull your plenum and check for washing inside ( gold tone in color). If your Cpi and nut kit are OK. Everything inside should be black. If not, you nedd to replace your CPI and nut kit. All the other parts like plugs, cap, rotot, and wires are good to replace, but won't correct the trouble your having. Make sure that you change your oil and filter after you have replaced your CPI. Don't run the motor until you done that. The oil is contaminated with gas and will destroy your motor bearings and oil seals. Here is a excellent link on step by step of a CPI replacement with pictures. Let us know what you come out with.
http://www.automotiveforums.com/vbulletin/showthread.php?t=473110&highlight=cpi

i just poured a 4.5 quarts of mobile one synthetic in...

what i dont understand is why he has 2 threads on the same thing. in his tuneup thread you all told him cpi nut kit then he starts this thread about the same thing when he knows what to look for and to search as there has been a great deal of cpi threads lately and even ones with pics. The one you gave Gabe is what im talking about.

wheres the imtv?

also if i can get a 4.3 vortec for 400 is it worth it to screw with this one?

wheres the imtv?

also if i can get a 4.3 vortec for 400 is it worth it to screw with this one?

its directly under the VORTEC plate on top of the intake plenum. Remove the plate (2 torx screws) then you will see it sticking up... it has an o-ring on it to create a seal so be careful when you remove it so you dont damage it.

black as night in there.. its like an oily black is that right its shiney

OK, Are you looking through the IMTV or did you pull the Plemun off? The best way to get the whole picture is to pull the Plenum. Alot of times its hard to see by the nut kit.

I suppose i should have said that you will need a flashlight to see down in there. yea, its supposed to be dirty in there so if it seems too clean then you prolly have a fuel leak. You view will be limited but it is a good start without having to purchase any gaskets.

i could see fine it looked like someone took old oil and poured it in there black and shiney like old oil

lookin in the imtv.... i woul just pull it all off but it 10 degrees out side windy ashell and my gf's moms being her usual bitch self and wont let me use her garage....she has an 8 car garage out back and a 1 car over size in the back... she as so much shit in her 8 car that she can barley fit her grand vitara junk in it.. she has the front open and the back hole open because her and her husband are at work and she wont let me use fukin bitch...

Did you check at the sharder valve to see if you have around 60 to 65psi, and do a leak down test. You shouldn't loose any pressure for about 3 minutes.

no dont know how.... remember..this is my first american car the vortec is way diff than my vtecs