Hello all. I have a 94 4dr 4.3 that is having a very serious issue. About 3 weeks ago, while driving home, my truck just died on me. THe problem has been geting worse. Here recently my blazer will start, and run fine for about 10-15 minutes, then it sounds like it is missing(under acceleration). The problem seems to be mainly between 2500-3500RPM's. At park I can slowly give it throttle and at about 2500 rpm' it begings to sputter/miss. I have changed plugs, air filter and checked my spark, nothing wrong there. I have had to have it towed and had two mechanics look at it and they are stumped. The last mechanic said it it threw a code(???)that mabey suggeested an o2 sensor and that it appeared to be leaning out. Anyone had this problem, if so any suggestions would be nice. Btw, I am in alabama, so if anyone else lives in this god forbidden state let me know. Mabey a get-to-gether is in the future???

 

Did they check your fuel pressure?
When is the last time you changed your fuel filter.

 

Actually, my fuel pump and pressure was checked yesterday at the mechanics. it was good. also, i changed my fuel filter 'bout a month ago. Would a carbon deposit cause this problem?

 

Just got back from another mechanic today. He scaned my blazer and charged me a whole 50 dollars to to tell me my truck is throwing a code 43, knock sensor. If anyone has had to deal with these let me know. I hope this wil fix my problem. BTW, I used some seafoam today and the problem got a litte better.

 

If this problem just, all of the sudden, started happening, I'm betting that the knock sensor is at fault. On my 2000 4.3L, the knock sensor is located on the bellhousing extension of the engine block under teh oil pressure sending unit, to the drivers side of the distributor. I'm not sure if it is in the same location on your 4.3L or not, but it shouldn't be all that bad to check that location.

I wouldn't think that carbon buildup would cause a problem so suddenly. If you wanted to, you could try a seafoam treatment which would serve to clear the carbon out of the valves & pistons to a certain extent. I'm about due for a second cleaning (probably this weekend) because I don't think the first run cleaned it enough.

 

not sure about the knock sensor code, but when our '94 jimmy started doing something similar, the problem turned out to be bad fuel return lines (it also had problems starting).

 

Crawl under your truck and beat on your cat. Does it rattle? Have you ever had it changed? Can your truck idle and run all day long if you keep it under 2K rpms?

You might be due for a new Cat?

 

Update. I finally broke down and bought two new knock sensors from O Really Expensive auto parts lastnight. I spent aobut one and a half hours moving crap out of the way just to remove and replace the back knock sensor. Pain in my ^$$. I replaced the driver side and rear sensor, pluged every thing up and tried to crank her. Nothing. It would turn over, start, then spit and sputter. CRAP!!! At the point I was about to thorw in the towel, I realized my truck was most likely 180 out. Yes I had to remove my plugs and cap to access the rear sensor. As I sat there, with my truck running like crap, I had a very rude awakeing. Sputter, Sputter, BOOM!!! Backfire. Very Loud. OW my ears. I had neighbors coming out of there apartments wondering what in the home of satan I had done this time. BTW, I am kinda known as the local redneck-DIY guy. I guess the backfire would not have been such a big deal, but considering I did not hace any type of plumbing before the throttle body and the only exhaust is a cherry bomb that has no after piping, just dumps, but IT WAS LOUD. I decided to give it up for the time being and will try to get it running today, hopefully without pissing off the neighbors. Just thought I would let ya'll know what was going on . Thanks for all your help. I will post some pics very soon. BTW, the cat is fine and my fuel return lines are ok. Thanks for your help. I am sure I will be back with more questions in the future.

 

You stated that you have replaced plugs, air filter, and voltages are fine, but did you inspect/replace cap. One thread mentioned that a small hairline crack in the cap/rotor was his problem...sometimes you have to dig a little deeper in the forums to find a solution... Also have you had the ignition module checked it might be worn or a wire is coroded and not making good contact.

 

I am pretty sure my problem is more along the lines of timing/plug placement. I did make any attempt to remember what plug wire went where. Now I am stuck with trying to find a shop that would know the firing order, and cylinder numbers on my truck I am so fustrated with myself. Guess I just wasnt thinking due the fact that I was outside late last night. Does anyone know the correct firing order/cylinder bank numbers on a 1994 S10 Blazer(boxy style) 4.3w code on the vin, auto transmission 2wd. Any helpm would be apreciated. Also, if the only thing I removed is the dist. cap, will i have to adjust the iming?