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Vortec 4.3L misfire

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Old 01-24-2006, 07:44 PM   #1
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Vortec 4.3L misfire

Okay, so Im not a real experienced mechanic. In complexity, my knowledge barely covers TBI. CPI, MPI, etc. is beyond my knowledge.

Here is what I know:

My Blazer is a 1992 with a Vortec CPI injected 4.3L with 187,000mi.
It has ran kinda rough since I bought it, which was easily explained by the missing plug wire.
I bought new cap, rotor, plugs, wires, and filters for it.
It still ran rough so I started trying to diagnose it to the best of my knowledge.
I used a test light to ground the plug wires out at the top of the distributor cap one by one.
When I got to #2, the idle didnt change much.
I checked the spark, and it was very healthy.
I ran a compression test, and got 90psi out of it. Not too shabby.
So that leaves the fuel system at fault.

Any suggestions?
Old 01-24-2006, 09:47 PM   #2
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Re: Vortec 4.3L misfire

first scan the computer for troublecodes. that should point you in the direction of what is wrong. when you replace what every part you need erase the computer. pull the ecm fuse for 10 to 30 secs to allow the computer start fresh. and drive it around so the computer can get used to your driving habit. plus check the obvious filter and oil condition, trans/t-case fluid condition. and see how she drives.
Old 01-25-2006, 08:33 PM   #3
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Re: Vortec 4.3L misfire

This is all I got:

32 - Exhaust Gas Recirculation (EGR) Circuit - EGR open command did not change the fuel mixture when the command was given during off idle operation. EGR opening should cause the mixture to be slightly richer because of the low oxygen content of exhaust gas.

This shouldnt cause #2 cylinder to misfire, though, Ive always thought the exhaust smelled rich.

So, does that trouble code mean that my EGR valve is shot?
Old 01-25-2006, 09:56 PM   #4
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Re: Vortec 4.3L misfire

It could be ether the solnoid is shot cuz it couldn't close it, or the valve is shot or the valve is caked with carbon

Last edited by madscientist101; 01-25-2006 at 09:58 PM.
Old 01-26-2006, 10:01 PM   #5
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Re: Vortec 4.3L misfire

I had a similar problem. I posted a picture of what I found when I removed the upper intake plenum. it's in the following post:

http://www.s10forum.com/forum/f107/93-blaser-poor-performance-226064/

Mine's running great now.
Old 02-01-2006, 10:12 PM   #6
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Re: Vortec 4.3L misfire

WOW... that is.... wild...

Im going to pull my upper plenum off this weekend to take a look. Hell, Ive got to pull the plenum to replace my EGR valve anyway... Might as well test things while Im in there...

Another thing Ive noticed with my Blazer is the fact that after driving it awhile down the highway, it starts to smell like something is burning! Though, once I get it pulled over and start searching for the smell, its gone! And the smell is like nothing Ive ever smelled before... I have no idea what it could be.

Oh well. Like I said, Im going to pull that plenum this weekend. Ill post what I find...
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