ok, so my 3rd gen has a carb, but my daily driver is a c1500 with TBI and this site seems to have the best collection of poeple to help when it comes to this system.

so ill cut to the chase with a lil history. the truck has been parked for about 7 months.(we were giving my g-moms 4 door subaru when she passed and with kids, 4 doors became a must) i missed driving the truck so decided to give it a minor tune up and oil change first. everything ran fine when parked and still when i started it back up after its rest. the tune up consisted of just cap, rotor wires and plugs (and the oil change).

so i started driving the truck everyday again over a week ago and everything ran perfectly. like it had for the last 234,xxx miles.yesterday i had to run all over the place and it did great, then this morning (a freezing morning at that, like 28* cold) it started and was running rough, i just figured it was cold and seeing as how i live 10 blocks from work it never had a chance to warm up. so when i leave work i sit and let it get some temp to it before pulling off and the "miss" is still there.. had to run to an appointment about 20 mins down the highway and it seems that anytime its under any load it has this miss. i got almost to my destination and pulled over, popped the hood and dripped a lil water on each primary header to see if its just one cylinder is having the issue (it has long tube headmens on it) and they all steamed up something feirce, also checked to make sure the wires were all on tight and one didnt pop off the cap or a plug (all were good). next thought was old/bad gas from sitting. it had less then a quarter tank (when i started driving it again it still had almost a full tank) so i added some dry gas and filled the tank back up. still missing under load. next i take off the air cleaner housing and hook up my timing light and watch the injectors to make sure they are firing right/good spray pattern and that was fine. at this point i noticed that when its off, one of the throttle bore blades has some stuff on similar to how coolant looks when a head gasket is bad, and it goes away when the motor is running. and i also see the fuel pressure reg. is wet and so is the body under and around the reg. is wet also. figured i might have a torn diaphram i replaced that and checked the spring as well. still the miss continues.

so like i said, it misses while under ANY load. at idle i sounds like there is a very slight miss and while just cruising it seems smooth, unless your in 5th gear it misses while trying to mosey down the road. its a 91 4.3l v6. with no cat convter.

can anyone guide me in the right direction..? anyone experience this? im sure its something simple and ill prob when it gets figured out. but im not into throwing parts at cars and its way to cold out to try and test every component until i cant feel any of my limbs... and my 84 camaro is taking up the garage with a partially torn down motor still in the car waiting for my hoist to magicaly re-appear from the last person who borrowed it.

 

Make sure the disributor is not worn & sloppy.

 

i ordered a fuel pressure test fitting and guage and also an adjustable fuel pressure regulator for it tonight. at least this way i can rule out the fuel system if there isnt proper pressure.

 

You can borrow a temporary fuel pressure gauge at auto zone. Has an adapter for TBI. WOT while in park and the pressure should not drop and should be 9-12 lbs steady.

 

I should know this but isn't the TBI still considered as EFI and be running at roughly 43 PSI? I though 12# was only considered to be a Straight carb with a mechanical fuel pump on the engine.. Or does the TBI run a mechanical fuel pump?

 

TBI is typically 12 lbs however some run higher FP. My TBI is at 25 lbs. TBI pump is good for 12-13 and TPI pump is good for 43 lbs and more. I think carb is 6 lbs.