Ok we are working on a 94 s10 4x4 blazer 4.3 vortec. Truck starts fine ( has bad battery and exhaust leak ) truck idles fine it seems to ride fine when not accelerating. Now if and when I give to much throttle it will begin to what seems like missing, as soon as I let off of the throttle and just cruise not accelerate it does not do it. Now my old blazer had the silver and orange vortex cover on the top however this one does not it has a black manifold but it is a 4.3l vortex I do know that but are there different versions? Some one else her told me to check the fuel pressure now correct me if I am wrong. I need to have the truck off hook up the gauge then turn the key on and should give me a reading? What are the numbers I am looking for? Now I have all the basics to do to the truck but I am wondering if I should hold off and fix this problem first so I do not ruin any of the new parts I am going to be putting on my truck. Here is what I have exhaust gasket, fuel filter, plugs, wires, air filter, battery, cap rotor, pvc valve, oil, and of course filter. Any help would be greatly appreciated. So aside from the above I would think it would be a fuel issue. From reading around in the forum I do have my doubts though it starts everytime and does not seem to want to die at all just hesitate (miss) I can shut it off and always starts right back up. Thanks again for all the info!!

 

Fuel pressure test should be between 50-60 psi with key off the important part is to watch if the pressure drops after the pump stops running after the initial prime sequence, if the pressure bleeds off steadily it is a sign of an internal leak. Another option is remove the vortec cover and the wire harness beneath it (4 screws total, 2 on the cover and 2 on the harness) and look inside for clean areas, clean pass side = likely fpr leaking, clean driver side = likely spider and/or nut kit leaking. although this method of opening and looking is not fail safe (could be left over signs from a previously fixed leak) I prefer a pressure test so save throwing money unnecessarily at a problem in hopes of a fix.

A little background on my experience with this (my truck is a 94 also) started right up and ran fine (with horrible gas mileage) would bog down when accelerating and from behind the vehicle had a fairly strong fuel odor coming from the exhaust while running, i tried several ideas to fix it, cleaned egr and put in screened gasket, replaced several sensors, new plugs wires cap rotor, fuel filter with a small increase but never a true fix finally i was visiting a friend an hour away from home when the truck just refused to start acted like the motor had seized luckily for me searching for an answer is when i found this forum posted my issues and was quickly informed to check the fpr/spider you have no idea how happy i was to find it was just a $45 fpr and not a new engine i needed.
That being said, I do not know for sure this is your issue but it sounds an awful lot like mine did at the time which is why i suggest pressure test first to save yourself the time and money I wasted trying to find the problem.
The black upper plenum the only difference is paint the engines are the same there are people that say it was due to an early recall of some sort (i forget the details) but its just color nothing to worry about. Hopefully I explained all that right if not someone will correct me soon enough Good luck and keep us posted what you find.

 

ok i have a black manifols but the silver/orange thing you talk about is not on my engine i did not take it off is it missing or do they not all have that?

 

that im not sure of mine is the common plain jane aluminum with the cover but personally if it were me id see if i could find the vortec cover in a junkyard and slap it on just for the cleaner look.

 

Yeah I am gonn look for one I just did not know if some just dont have to cover. Thanks I will let ya know the outcome hopefully sunday!

 

Ok also do i have a MAF could this also be my problem ?? And where is this located thanks

 

If I remember right the 1st gens did not have a mass air flow sensor (I know my 94 does not)

 

ok cool WOW i have never been so excited to go to sleep so I can wake up lol. I am going to get to work on this 8am tomo will let you all know the results as well as some pics! Thanks for all the info thus far

 

Ok so i fixed the exhaust leak (pain in the six) replaced plugs, wires, cap, rotor, fuel filter, air filter. oil, oil filter, and pvc. I could not get a hold of a fuel pressure gauge so hopefully I can do that tomo. So the outcome is it is not that bad but it is still there starts fine idles fine. When you try to acclerate bogs down or misses. Could cruise fine at 55 with the air on. So with the exception of the fuel pressure say its is not good what would it be and again if its not the fuel pressure what would it be. Now as far as my intake and crap goes is this the cpi?? or do i have that 1% with the other kind of intake...... Thanks In Advance
http://i268.photobucket.com/albums/j...hort/truck.jpg

 

That is a CPI if it was the less than 1% it would be TBI (looks similar to a carburetor) as for other options, remove and clean the EGR but make sure you get the screened gasket for reassembly (wouldn't hurt to do this regardless of the fuel pressure test results) other than that id say let it ride til you can get the pressure test done I really don't want to suggest just throwing money at a problem without some testing beforehand the egr thing is quite common which is why I suggest going ahead and cleaning it anyways the cost of a screened gasket is worth avoiding the clogged egr again down the line.
IF you do end up having an internal leak have a look Here should explain all you need to know about the repair if you have to go that route.