Hello everyone!

My 1995 chevy blazer (2wd, 4.3 cpfi) runs rough and sputters on acceleration and SES light is not on. I have spent hours searching this site and Google and cannot find an answer.

Here is what I have replaced:

fuel pump/filter
distributor cap/rotor/wires/spark plugs
Fuel injector is about 1 year old

Could the injectors go bad that quick? What else could it be?

 

Have you checked fuel pressure? The fuel pressure regulator seems to be something you've overlooked.

 

Take off the EGR valve and check /clean it if there is any carbon build up on it.. a memebr on this board who is a personal friend had that same prob and cleaning the egr valve helped.. If that does`nt help let us know. was the truck having this problem b4 all the new parts??

 

Thanks for the suggestions. I tested the fuel pressure and it was doing some weird stuff - first I got a reading of zero with key on engine off BUT
the truck started! Then the pressure was at 55psi

Tried it again with key on/ engine off and the pressure was around 58psi and again started fine.

So I did a little more research and here is what I found could cause a stutter on acceleration:

MAP sensor
Throttle positioning sensor
Air Charge Temperature Sensor?????????
Distributor/timing


The ACT sensor really surprises me but someone claims it fixed their "chugging" problem.

The Distributor is really hard to get to and I dont want to mess with it unless it's the last option.

There is also a crankshaft positioning sensors/camshaft sensor but I dont know if they would cause this problem??

I will replace the above sensors and if that doesn't fix the problem I guess I can always return them......but I have a feeling it wont be that easy. It could be a problem with the pressure regulator which is on the spider?? So if I have to replace the spider I might as well throw on a new distributor as it does look a bit rusty.............uhhhhhhhhhh

 

Oh yeah, when I replaced the spider last year the intake was really carboned up and my friend suggested I block off the EGR valve.

Would a blocked EGR valve be a problem? The SEL would come on at highway speed but otherwise the truck ran okay - but has always had a rough idle, now the stalling/sputtering on acceleration.

I heard the engine runs hotter without the EGR but recirculating exhaust back into the engine doesn't make sense to me. I blocked of the EGR on my 2000 Silverado and it runs fine - though it does throw a code for low EGR circulation.

Besides I dont think a blocked EGR could cause rough idle as it's supposed to be closed anyway at idle or stumbling on acceleration.

 

could be your cats clogged . start the truck and put your hand by the exhuast see if the air is warm and if its coming out right if its hot it could be a clogged cat

 

Yeah, I thought about that. I took the Cat off my Silverado and that fixed the "mysterious" random misfire.

But I dont want my blazer to sound like my truck. LOL

 

well if it runs better with the cat converter off you found your problem. you can always put a new one on

 

I havn't taken the cat off the blazer yet. Anyhow I replaced the throttle positioning sensor, MAP sensor, and air charge sensor with no change.

I would like to replace the crankshaft sensor but it looks really hard to get to (like everything else).

I guess I will take off the plentum and check for leaks and while the space is "open" replace the distributor (the top is pretty rusted) and then get to the crank shaft sensor.

But if I'm going to do all that I might as well replace the intake gasket as they seem to fail frequently.

And I'm going on vacation next week so this project will have to wait a bit........but I will update the thread as I go

Thanks everyone

 

Hey try cleaning your mass air flow sensor.. I had simular problem where the truck would sputter.. Buy some sort of cleaner, carb cleaner, mass air flow cleaner etc.. spray it, and then take a q-tip and soak the the q-tip in the cleaner, then procede to whip around the contacts.. Alot of crud went onto the q-tip when I did it.. After a few times I got all of it off and it runs like a champ now.

Good luck