i got a 92 s10 Blzr with a 4.3 TBI, for the past couple of months, i've been having an issue when at a red light or stop sign, the car would just start shaking until it either stalls or goes back to normal idle. it doesnt do it all the time, only when it wants too. another funny thing is that if i would to let stall whiled stopped, the car starts up fine and continues to run fine until i reach my destination, then the next time i start it up, it either run fine or start shaking again. when it does the shaking, and the car stays on, the exhaust smells like it running rich on gas, but when it its running fine, the smell goes away, now since this problem has been around for a while, i've changed the spark plugs twice because they get a huge amount of carbon build up. the wires, cap&rotor are fine. at one point i thought that the TPS was the cause of it becuase when i would move the wires from the connector the idle will get rought then back to normal, or the idle jump up then back to normal, so I sort of pin pointed what i thought was causing somesort of short and snipped the three wires and cut off a section for the wires and replaced it with new wire on that section, and it ran fine for a couple of weeks but then it started happening again and now I dont know what else to check. i even took it to a shop and the mechanic hooked up a scanner and said that nothing was coming up even tho the check engine light was coming on when it went to rough idle. he did say that the scanner was communicating with the computer but that no codes where coming up.

Pleaes help before I blaze up this blazer.

 

does anyone have any suggestions on this?

 

so i finally got hold of a scan tool, and picked up the codes that were stored in the computer. it had codes 15(temp sensor), 22(TPS low voltage), 36(O2 low voltage), and the 2 codes for running rich and running lean but forgot what numbers they were. Is it possible that all 3 sensors went bad? i've replaced the TPS a few months ago when the issue first started, but havent replaced the o2 or the temp sensor.

 

I just replaced the O2 sensor and still having the same issue

 

I honestly wouldn't think it would be the o2 sensor. Disconnect the negative battery terminal for 5 minutes to clear the codes. Run the truck to get the newest codes. We will go from there.

 

I would lean more towards a leaking EGR from the sounds of things.

 

what should i check for on the egr, its one with a vacuum hose on it, didnt see any cables going to it, is it fairly easy to remove and clean?
also, i posted another thread on rough idle, the blazer overheated to the point where i could hear the knocking of the bearings but once it cooled and oiled up it sounded fine but not seems to shake like its missing. it has new plugs, wires, cap and rotor, but i did seem to notice that under the rotor, there was a brass looking sleeve that seemed to feel really loose, i was able to rotate it left and right but not all the way around, but it had alot of play on it, is that normal?

 

sorry to revive an old thread.. but having similar issues.. no check engine light, but vibrates and stalls randomly. did you get your issue resolved? thanks!

 

Some info on your truck would be helpful. Do you have a TBI or CPI engine?

 

The O2 sensor code will trip due to the engine running rich, it does not necessarily mean the O2 sensor is bad, its just detecting the air to fuel mixture ratio is to rich or lean.
This issue could be the IAC (idle air control valve) this unit adjusts the ratio of fuel and air.

Check/replace the IAC, EGR, run the engine and check for codes, be sure to clear the codes after the fix/replacement.
Prior to removing/repairing these sensors disconnect the battery.

Check for leaking vacuum lines, this could cause a rough idle.
also water in the fuel may cause a rough running engine.