got at 94 s-10 blazer 4x4 4.3l vin-w engine. out of nowhere yesterday it died and had trouble starting but did, now it has trouble idling engine runs better the higher the rpms get. i change plugs (gaped to .045), wires, cap and rotor and got no change. i had it at idle and pulled the three plug wires on passenger side and idle went almost back to normal but exhaust started to smoke black, not a lot of smoke but it would stain a paper towel, the coil does have a orange/blue color spark, im not sure it should be all blue or not. any ideas on whats wrong with this engine?

 

[&:] I would check the EGR valve. What your describing is exactly what mine used to do on my 94 4.3 Astro van. It's electronic and not vacuum operated. Pull it off and check it. The pintle is supposed to move in and out but it carbons up and gets stuck. Ususally you can clean it up and get it moving freely and your good to go without replacing it. Should set off the 'check engine' light but I had a 94 4.3 and it didn't always set it off. It looks like a little motor with a connector on it on the front of the engine. Doesn't look like a pod like the old ones.

 

One other thing I should have added is that these engines are notorious for the poppet valves sticking and when they do it will run like garbage. They made some modifications to it in 1995 that help but it's quite common on the 1994 W engine. Aside from following the GM service procedure, my brother in law told me to dump some Chevron with Techron fuel system cleanerin the tank. He is an engineer at the GM tech center and he said they ran tests to see which aftermarket products would help this particular problem. That was the only one they found that would actually work. I tried it and it actually did work for me (and it was running bad too). I ended up getting 300K miles out of that motor by dumping some in there once in a while. Still ran good when I sold it. It's about 5 bucks a bottle at most department stores or auto parts stores.

 

my 94 4.3 vortec did the same thing,it was the fuel regulator&spider injector leaking into intake

 

thanks filstoy, egr valve was stuck open. i cleaned it out and now it runs like a champ. thanks smokey for your reply also, unfortunately i went down that road this summer and puta new regulator & spider injector in. and that a expensive road too!