they put in a new computer today, and still no change. this is getting ridiculous, half this truck is brand new and it still wont run, im out of ideas and think its time to move onto a new car im thinking trailblazer SS, but if you guys still have any ideas as to what the problem could be let me kno please.

 

There has been a lot of recommendations from us with very little follow up from you. Here is a quick summary:
[ol][*]Have you verified the fuel pressure does not bleed down? - swartlkk[*]Have you tested the compression? - swartlkk[*]Have you tested the spark timing? - swartlkk[*]Is the pump humming at all and what is the initial key on and crank pressure? - JP[*]Check the EGR? - Mammys Car[/ol]I am sure you do not want to keep throwing parts (and your money) at a problem in "hopes" that it will be repaired. Questions have been asked because they help narrow the focus of the diagnosis. Specific answers would be nice.

 

All of thoses test have been preformed by the shop. and i cleaned the egr before i brought it there

 

Steve, how well do you know this garage and do you have faith in them? I ask because it seems that they did not even know about the OBDsituation withthe '95 model year. Plus, from your posts, I don't see a reason for them to so quickly assume that the PCM would be at fualt.If they checked all the items Kyle asked about, did they also check the ignition coil?

 

Try a crank shaft position sensor. This happened with our old astro with the 4.3 in it. It would start and run like complete crap, or it would not start at all. And a few times it started and ran fine, then would just ramdomly die. My dad went crazy with that one and changed every thing on the motor for the ignition system, plugs, wires, coil and a couple sensors.
Also, I know you said that you just changed the cap and rotor, but I did one on my blazer, and within 8k miles it had already went bad, and I was also getting spark. Same thing, would not start at all. I do know of one other person that this happened to too around me. Did the truck show any signs of a shudder at any speeds while cruising? Or when stepping on the gas before it died? That is what happened just before mine had died. as soon as I put a new one on it started right up. (I know, I have mentioned this in a few posts now, and it may not be relevent, but it sounds like what mine did, and I spent close to $400 only to feal like an idiot when it was as simple as that, and only I think $60 total) So hope fully it helps, and it if don't, well sorry and disregard.

 

That may be all fine and well, but without results that WE can interpret, it is awful difficult to be able to give you direction. We could play the guessing game, but that is not something I enjoy for multiple reasons.

 

Got it back from the shop yesterday. Replaced ECU, Fuel pump, fuel filter, sending unit. drove it last night seemed fine, drove it this morning and it still bucks. Only at a certain throttle postion though. it seems when its cold it runs fine then when it warms up it starts to buck. it does it when i accelerate from a dead stop, and during low rpm acceleration. besides that it runs and drives fine under half throttle and full throttle. this is driving me crazy. Any ideas maybe fuel injector cleaner or something. the shop did put in like 4 cans of dry gas before i picked it up to get the moisture out of the tank, could that be making it run rough?

 

replace the fuel pump relay when they start going bad they do great when cold but once warm they function poorly cant check them when cold they will read okay take a very warm rag put it on the relay and then check resistance and then once cooled down check again

 

For the fuel pump relay you can also switch it out with many of the other relays such as the horn relay for testing purposes. Just be sure it is the same relay number.

A few other things that you can check is the catalytic converter for one. Crawl under and give it a couple smacks and shakes. Anything rattling in there?
If so then the broken pieces of your cat could be restricting exhaust flow.

A bad TPS sensor can also cause your symptoms. This is another part that can also test differently on occasion between warm and cold and I would recommend testing it in both conditions if possible.

A quick search of this forum should give you the exact procedure for testing the TPS sensor.

 

it sounds like your problem could be the ignition switch module have you had it checked at a parts store when the ignition switch module starts to go bad it will work fine until it starts to warm up then it starts causing plugs misfire and will cause your blazer to die then when it cools down it will work fine until it heats up again i had that problem before