1991 S10 - Blazer 280,000+ miles...
This issue made itself known today.. (couldn't find a thread similar anywhere)
After engine warms up and auto-choke kicks down the throttle will suddenly increase in speed then drop down - run rough for a moment then smooth out.. Doesn't show up as a pattern. Just does it when it wants to. Any clues out there ??

 

Any Check engine lights? You can try to clean your TPS carefully...

 

tps? you mean the iac. rich,go home you drunk LOL.


OP. on the throttle body,passenger side. round can looking thing. unscrew it with channel locks. clean it with brake cleaner,and inside the throttle body too with a toothbrush. reinstall and see if it fixes it.

 

Rich - Chris,, Thank You for your valuable time. really appreciate it.. Rich's question is very valid. (i forgot to state the status of the C.E.L. in the original question) Rich,, Yes.. The light comes on when it starts messing up and shuts off when it's done
Please forgive me, I need to brush up on my engine component abbreviations. Exactly what is an "iac" ??

rick

 

Chris was right on both accounts, I meant IAC, not TPS, and i was intoxicated HAH

IAC (idle air control valve)

Since the CEL comes on, have you had it scanned for stored codes?
here is how to read the code yourself

Service Engine Soon light on? Check Your Own Codes (OBD1)

 

Hi Rich,,
Thank you for the guidance (and for being honest) Removed the iac, Looks clean. Question though.. I am unfamiliar with this component. Is the plunger supposed to be able to be pushed inward with moderate thumb pressure ?? Attempted to and it don't budge. Codes I got back were #22 (tps out of adjustment) & #24 VSS (Vehicle Speed Sensor).. #24 is coming up because I lost the speedo months 'n months ago.. Didn't figure its a biggie. So what do you think so far ?? Oh, also forgot to mention that I had to smog the thing for registration. This issue arise'd the day after the smog was done. (didn't know if this would matter or not)

I don't believe I have forgotten anything else.. (i hope)

Appreciate your advice, sir..

rick

 

on a 91,with it being a non computer controlled trans,the speedo isnt a big deal,other then loosing cruise control. (if you have it,lucky you,i didnt when my speedo died)

tps though,can cause some weird issues. Id replace it. its about 25 bucks. takes 5 min to replace.

 

Sounds to me like your TPS is bad, its not recommended to push the plunger in with your fingers, but since you tried and it did not move, that is not normal.
as it should move.

I would replace it with a new one, like chris said, they are pretty cheap.

 

the iac...i remember when i did mine it didnt push in,which i thought was normal as the tbi style is apparently adjustable by turning it. Which i wouldnt do,i messed mine up and never could get it right again. had to get another one. If you want,try another iac. If nothing changes put the old one back in. takes a whole 2 min to do it.

 

Hi Guys, , I'm back.. and deeply apologize for the mega delay in revealing my follow-up on the 'erratic idle' issue
(( I have MS.. unfortunately i had some 'down-time' days hit me right after i installed the new IAC valve. ))

Replacing the valve was the correct treatment. So far no need for anything else. Works Fantastic !! !! By myself, it wouldv'e taking me weeks to troubleshoot this issue. (due to my lack of knowledge with fuel injection setups..) Give me a carburetor any day and i am all over that thing with the knowledge to boot.

Thank you, all of you for your assistance.

ricky