91 Chevy S10 4x4 v6 4.3L Idle issues

I'm having an issue where my S10 fights to stay alive while idling. Some days are worse then others, but basically the truck alternates between high and low idling very often. Also, a distinct hissing sound is constantly heard through the vents except when the rate of change in accelerating increases. I'm thinking its a vaccum leak issue. What is the best way to test for vaccum leaks? Other suggestions?

dude! I have a 92 s-10 and I have exactlly the same two issues. Gas mileage sucks as well 10mph city and 16 highway. I have a 97 s-10 truck with same motor and i get 17 city and 22 highway. I have fully tuned my 92 but no success. I will be checking my map sensor then throttle positioning sensor, then If neither of those work I'm cutting my cat converter out to look at possible issues there. I will try to get back if I have success with any of the listed attempts Ryan@permapost.com

napa seels map sensors for aaround 70 and tps for 20 first I am going to try and clean my map tonight and see what happens, I will respond when I find something, Ryan

Same "problem", but not. You see, fuel pumps go out. After 12 years mine did, and I replaced it with an auto zone pump. That is when the problems like you talk about began. rough idle, bad mpg. Thought tune up, map etc. Finally the new pump went out, replaced it and the other issues went away. But soon they were back, only that pump never went out, just got real noisy. So I went to Carquest, bought an oem Delphi pump, and it runs like a champ. All idleing issues gone, purrs like a kitten. CPI units do not need junk fuel pumps. Carquest pump was the same price as auto zone. I then made autozone eat their pump, so I broke even. PS, keep that tranny cool, or else.

I think I just have a vacuum leak in a line somewhere.

Im having the same problem too with my 91 s10 4.3 it will idle real low then raise back up to 1500 rpms, and sumtimes it idles so low it dies. yall might need to check ur engine codes, mine says its the map sensor

i have a 93 s10 4x4 and all the above probloms happened i changed mt tps sensor and bingo idle fixed. i would try that first, it fixed mine.

91 S 10 Will Not Start After It Has Rained New Spark Plugs, Wires, Distributor Cap, Rotor When Block Heater Is Plugged In For A Few Hours It Will Start And Its An EFI

i have a 91 s-10 4.3 auto 2wd....my dad left it to me and i really want to fix it up. so far i've replaced the fuel pump and filter..oxygen sensor..egr valve..map sensor..vaccum selinoid..coil..ignition coil...tps..knock sensor..both coolant temp sensors..plugs wires cap and rotor..idle air control all vaccum lines..entire exhuast system...now has dual exhaust....and the esc module and the ecm. the problem is stalling and cutting out. code says map sensor....i'm on the 3rd new one. lacks power up hills and will stall after just seconds at lights.i have replaced the tbi also....ireally want to get this truck running properly..every garage has shakes thier head and tell me to let them know when i figure it out...this truck belonged to my dad..its got a new paint job and rimms and i want it to run like it should...help if you can....thanks in advance.

take ignition module in and have it tested

slysayshi wrote:

i have a 91 s-10 4.3 auto 2wd....my dad left it to me and i really want to fix it up. so far i've replaced the fuel pump and filter..oxygen sensor..egr valve..map sensor..vaccum selinoid..coil..ignition coil...tps..knock sensor..both coolant temp sensors..plugs wires cap and rotor..idle air control all vaccum lines..entire exhuast system...now has dual exhaust....and the esc module and the ecm. the problem is stalling and cutting out. code says map sensor....i'm on the 3rd new one. lacks power up hills and will stall after just seconds at lights.i have replaced the tbi also....ireally want to get this truck running properly..every garage has shakes thier head and tell me to let them know when i figure it out...this truck belonged to my dad..its got a new paint job and rimms and i want it to run like it should...help if you can....thanks in advance.

i not a trannie guy can someome tell me why a 1997 s10 4.3 4x4 won't shift pass 2nd gear when this truck came to me the head was cracked and engine was hyro locked but now repaired and now the trannie thing it was working before the motor was over heated

RATTSASS240 wrote:

SOMEBODYS GOTTA KNOW WHATS WRONG!!! MY 91 V6 JUST RUNS FUEL THRU THE INJECTORS AS SOON AS I HIT THE KEY INSTED OF JUST THE SMALL SHOT TO GET HER RUNNINCAN ANYONE PLEASE HELP IM AT A LOSS AND CANT AFFORD TO JUST START CHANGING PARTS TILL I FIND IT IM GUESSIN I AINT THE ONLY ONE TO EXPERIANCE THIS PROBLEM

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You may want to get a new throttle body. I picked one up at the junkyard for like 20 bucks. Good Luck.

This is short but to the point, it is the throdle control sensor i had the same prob, changed the sensor, fixed it right away, if u dont know where it is, on your throdle body, right side, the sensor with three holes.

N33D H3LP wrote:

91 S 10 Will Not Start After It Has Rained New Spark Plugs, Wires, Distributor Cap, Rotor When Block Heater Is Plugged In For A Few Hours It Will Start And Its An EFI

cap boy

Check you egr valve!(behind throttle body)they get carboned up and cause a major vacum leak.Also a known problem for rough idle.Here is something else.The early 4.3 was produced w/o a balancer shaft in the lifter valley.93 was the first and it was done to combat rough idle.I have a 91 with 31,000 orig.miles and I bought it from the orig.owner.I had been to the dealer 14 time for the same problem(rough idle)

My 93 Sonoma with 4.3 TBI Had such a bad vacuum leak , when I stopped at a red light the service engine soon light came on , then went out when I got going. I got a code 35 (unable to control idle) Found the base gasket of the TBI was almost gone. A cheap and easy fix. Now I just get a little rough idle when in gear. Seems like the tranny has some issues. Only has 275,000 miles on it !

I have a 93 s10, 4.3 automatic tranny. Just rebuilt the tranny and now a couple months later my instrument panel does not work and My tranny only has park, reverse and 3rd gears. I put a new speed sensor in and still same problem. Any ideas???? Need help fast.......Thanks!

RATTSASS240 wrote:

SOMEBODYS GOTTA KNOW WHATS WRONG!!! MY 91 V6 JUST RUNS FUEL THRU THE INJECTORS AS SOON AS I HIT THE KEY INSTED OF JUST THE SMALL SHOT TO GET HER RUNNINCAN ANYONE PLEASE HELP IM AT A LOSS AND CANT AFFORD TO JUST START CHANGING PARTS TILL I FIND IT IM GUESSIN I AINT THE ONLY ONE TO EXPERIANCE THIS PROBLEM

Just had the same prob and spent hours scratching my head, Check your temp sensor, the computer defaults to neg.44 degrees when it gets no signal back from the sensor, this happens on the crank cycle and floods motor instantly! mine was simply a bad conection but sensor failure will do the trick also. its located right on top of motor behind uper rad. hose outlet, good luck

so i have a 91 s10 pickup extended cab 5 speed and my 4x4 doesnt work at all but what part do i need and where is it located?