95 Chevy s-10 Blazer strange problem

Hello,

Well i recently purchased a 95 Chevrolet Blazer 4.3 Vortec from a local small dealership with 74,000 miles on it. It was leaking anti-freeze so we had to replace the water pump, now that is all fixed. It didn't pass inspection because it had bad ball joints, those also got fixed and now it passed. My major concern is that ever since I bought it it seems like on bumps or inclines when i keep a steady throttle it boggs/bucks like it wants to stall but keeps going, it's hard to explain. You can hear it in the engine also. The service engine soon light also comes on when this happens. I have gotten it checked everytime it does it and the code is for a map sensor low output failure. So we replaced the map sensor, and still boggs/bucks and the light comes on. We brought it to the mechanic and he tried cleaning the egr valve and it still does it. Can anyone help me, or has anyone had the same problem with there s-10 blazer? If so could you try to help me uncover what is wrong with my vehicle? By the way it is all under warranty still.

the map sensor low output code is because your intermittently losing manifold vacuum when the engine boggs down or stumbles. that code is not the problem. the ecm thinks that map sensor is the problem because it is reading low vacuum. the ecm doesnt know the engine is stumbling/stalling. the only thing you can do to find the issue is look at all the sensor data in real time and take a electronic picture of it when this problem occurs. then print the picture the scanner took. if you know what ecm sensor values are supposed to be then you can find the problem. unfortunetly, to do this you will need a high end scan tool. if you dont have the knowledge to do this then you will have no choice but to bring it to a shop. some advise to u is do all the maintenence/tune up on the truck first. you dont want to pay a shop big money only for them to tell you the plugs, cap , wires, etc. were bad when you could of done that yourself. good luck!

Just had a similar problem on my 95. I was convinced it was fuel related. Wires looked like new, but they were the problem. Tune ups are cheap, I'd start there.

Hey,
Thanks for the info, i really appreciate it. It just stinks when you get all hiped up about getting a different vehicle, and then it turns out you gotta have it in the shop everyday. But it will be worth it when it is done. I am going to bring it back to the dealerships mechanic so i don't have to pay for anything and i hope it gets fixed this time. I will tell you whats happens, and what it turns out to be.

Thanks,
Blazer95

Yip, this will be covered under their warranty.

Once the injector is fixed, the 1995 is bullet proof.

Follow up:

Well i brought it to the mechanic yesterday, and showed him what it did. Thankfully it did it. He took the truck for a few hours and did something in the wire harness. He drove it 25 miles and it didnt do anything. So we took it back. Today i have this incline in my yard and put it in 4x4 because it does it alot in 4x4, and it was doing it again. I am getting really fed up with this blazer. He believes it might be a throttle positioning sensor? or something like that. Could this be the problem? Help!!

This sounds like the wiring harness is corroded where it connects to the computer.

It doesnt only do it in 4x4, it does it in 2x4 as well. it just does it in 4x4 alot more. Could this be the throttle sensor thing?

Do U Know Anyone With A Scanner That Can Read Live Data? You Want To Look At All The Live Sensor Readings When This Happens And Only Then Can You Pinpoint Which Area The Problem Is Occuring. Without That Scanner We Are All Just Giving You Ideas Of What It Could Be Which Wont Help You.

Have you looked at the injector yet?

It does it more in 4 wheel drive because its under a heaver engine load.
The very first plase to look at is fuel filter and fuel pressure. There are about 300 different things that could cause your problem what we need is to rule out the basic stuff.
You said inclines when i keep a steady throttle it boggs/bucks like it wants to stall but keeps going that is a clasic sign of a fuel pressure problem.
Everyone MUST remember just because the vcm/pcm sets a code that does not mean that sensor is bad.
Next when was a full tune up done?? a bad plug or ign wire will to the same thing.
A bad tps ??? It could be but i would bet its not the problem
Spray the ign wires with water from a small plastic spray bottle while the engine is running and look for any sparks ,do the cap wires plugs, everything