94 Blazer 4.3 bucking when idle

My S10 Blazer is bucking and smells like rotten eggs all of the sudden. I bought it about 1 month ago with 91K ran a little rough. I changed the plugs, Spark plug wires cap and rotor after all was replaced truck ran very good. NOW all of the sudden it has started bucking and running like crap. I wanted to know if anyone elde had this kind of problem and if they did what was done to fix it. I do remember having an old Oldsmobile and it did this when the EGR valve went on it. Could this be?

Year/motor/injection system?

i had this problem turned out to be leaking fuel lines inside intake, i have cpi check the plugs if they are fouled on one side only that may be your problem. all three plugs on the driver side were fouled which indicated the fuel lines if they are on the passenger side it may be your fuel regulator

Year/motor/injection system?

1994 "W" CPI. Plugs changed 200 miles ago replaced wires cap and rotor. I also hear a strange noise under car when accelorating like a bird chirp. Just started when this problem started. If it is the EGR where is the EGR located and I also noticed you have a EGR Mod what would this be and does it work?

1994 "W" CPI. Plugs changed 200 miles ago replaced wires cap and rotor. I also hear a strange noise under car when accelorating like a bird chirp. Just started when this problem started. If it is the EGR where is the EGR located and I also noticed you have a EGR Mod what would this be and does it work?

Pull your upper plenum, look for signs of washing (where one side is cleaner than the other) If the passenger side is washed, you have a bad CPI unit, if the driver's side is washed then you have a bad nut kit... If you replace the CPI, replace the nut kit as a matter of course. As to what the EGR mod is, it's a restrictor plate (not block off) to more efficiently burn fuel in our motors... Look here...This applies to all motors up to 95 (even trhough it says 94)... Also pull and clean your EGR, wire brush and carb cleaner would work...Run seafoam through the engine (seafoam is available at napa and advance autoparts)...

Pull your upper plenum, look for signs of washing (where one side is cleaner than the other) If the passenger side is washed, you have a bad CPI unit, if the driver's side is washed then you have a bad nut kit... If you replace the CPI, replace the nut kit as a matter of course. As to what the EGR mod is, it's a restrictor plate (not block off) to more efficiently burn fuel in our motors... Look here...This applies to all motors up to 95 (even trhough it says 94)... Also pull and clean your EGR, wire brush and carb cleaner would work...Run seafoam through the engine (seafoam is available at napa and advance autoparts)...

I went home yesterday and pulled the plenum off and low and behold you guys are good. The passenger side was washed. I am going out today to buy the complete kit fuel regulater and nut kit. AutoZone has it for $270.00 for the fuel regulater I have to check the Nut Kit price. Also wanted to no a little about the seafoam. I looked it up on the net and from what was said it works good. My only concern would be. Will I have to change the O2 sensor and my Boshe Plugs that I just installed 200 miles ago? And also what would be the best way to put it into the intake would it be to funnel it into the brake pressure hose on the back of the plenum? Thanks for all the help saved me alot of $$ all this work can be done on my own very simple.

I went home yesterday and pulled the plenum off and low and behold you guys are good. The passenger side was washed. I am going out today to buy the complete kit fuel regulater and nut kit. AutoZone has it for $270.00 for the fuel regulater I have to check the Nut Kit price. Also wanted to no a little about the seafoam. I looked it up on the net and from what was said it works good. My only concern would be. Will I have to change the O2 sensor and my Boshe Plugs that I just installed 200 miles ago? And also what would be the best way to put it into the intake would it be to funnel it into the brake pressure hose on the back of the plenum? Thanks for all the help saved me alot of $$ all this work can be done on my own very simple.

The nutkit is a dealer item only, will runyou between 45-65 bux.. As to the seafoam, pour 1/2 the can into the brake booster line, immediately turn off the engine, let sit one hour...Pour other half of can into the crank case..Do oil change at 500 miles.. After the hour is up, drive the truck normally, don't punch it... You will probably smoke like a bandit, 5 miles should clear it out. You probably won't foul your plugs bad.. After you're done though, pull and clean the egr with a wire brush and carb cleaner, before putting it back on, run the engine and rev it a few times for about a minute to spew any carbon out of the egr port on the manifold..

Just a little info. when i changed mine out everything went super easy except for getting the bolt out that holds the retaining plate for the fuel lines it is a t30 torx. but you have very limited space to get it out and it is also hard to see . it is very easy to strip be careful! i stripped mine and had to go to sears to buy a low profile bolt out kit about 30 bucks, but i finally got it out. Also i installed a kleen screen gasket on my egr port it is a gasket with a fine mesh screen to prevent large chunks of carbon getting stuck in the egr. :sunglasse

If that doesn't solve your problem check the cat, unplug the o2 sensor before the cat, if it runs better you might have a blocked cat, that sometimes makes the car smell like rotten eggs a lot of times, i had that problem with my blazer, not to hard of a fix.

So what's the verdict?

I've got a '95 that just started doing the same thing this week.. haven't had a chance to get to autozone to get the codes out of the computer yet.. but I'm interested in hearing what the verdict is as well... may give some insight as to whats up with my truck.

only other additional thing is that mine engines been fluctuating between running normal temp and -hot- (enough to light up the check gauges light).. i replaced the thermostat about a month and a half ago.. and symptom dissappeared.. but it has slowly started creeping up into the orange zone again

-vballfun

When was the last time you flushed your cooling system? Sounds like you have a blockage

Had the radiator repaired last summer at a local radiator/A.C. shop. I do not know if they would have flushed the system as a test for leaks or not. Ran fine all winter and just this April did it start heating up.. However that was my thought (about flushing) as well, and was my next move.. just haven't been able to get to it yet. (looking at what little rises up into the overflow tank the coolant is looking pretty murky/opaque... shouldn't it be some degree of translucent?)

It should be translucent green...

So what's the verdict?

Well I purchased the whole CPI unit on ebay brand new ACDELCO for $150 should have it in a day or so. I am going to flush the system with Seafoam after the install. I will also check O2 sensor. Second problem is I have allot of clunking under the front when driving. I think it is U-joints or slack in Drive shaft?? Dont know. Also in the morning when I first start it and go ot back out of the driveway when I put on the brakes as Im backing a strange noise comes from under the hood kinda like the fan hitting the fan guard any ideas to this? All you guys have provided some very good answers and I thank you for all your help it has saved me allot of money. Hey has anyone installed the trailmaster 5" lift?