Stuck high idle - Toyota Nation Forum : Toyota Car and Truck Forums

umpqua123 · 02-13-2009, 10:04 AM

I posted here back in Dec. 08 about my 97 T100 3.4L 5spd that had an inconsistent idle. I tightened all the air ducts leading to the throttle body, looked for vacuum hose leaks, cleaned the inside and outside of the throttle body and MAF and throttle cables. Even after the truck is well warmed up (driven around town 20+ min), the idle sticks around 1200 and won't drop until I give the gas peddle a quick tap. Then it drops to 750. My fuel mileage has dropped from 19 city to about 14. It's driving me crazy...does anyone know what else I need to do/check out before taking it to a mechanic?

BamZipPow · 02-13-2009, 10:19 AM

I believe yer engine has an IAC...idle air control valve and it might be sticking. Is yer "Check Engine" light on? If so, did you see what codes were stored?

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BamZipPow · 02-13-2009, 10:24 AM

I think it might look like this...

Alan R McDaniel Jr · 02-13-2009, 10:27 AM

My "Check Engine" light has been on since 2000. Perhaps I should look into it or find the wire that goes to it.

Alan

BamZipPow · 02-13-2009, 10:37 AM

It should look similar to this...

umpqua123 · 02-14-2009, 02:25 PM

Thanks for the suggestion. The picture was helpful. I shot it down with MAF cleaner and removed as much black residue as I could with a towel and toothbrush. I took off the plastic electronic part and cleaned the magnets too. I put it back together and started up the truck. After about 5 min, the idle settled down to 1000rpm. A min more and I had to tap the throttle to get it to rest at 800rpm. I'll take it for a test drive to see if I still have the high idle problem. How do I know if the IAC is defective?

No trouble codes.

dj99 · 02-14-2009, 06:33 PM

If the IAC is like others I've seen, then all you really have to do is shoot brake cleaner (or carb cleaner) through the air passage it while you cycle the electric solenoid with 12V. If it's sticking, this should do the trick. Do not shoot cleaner through the coolant passages with the hose tubes.

BamZipPow · 02-14-2009, 09:31 PM

Quote:

Originally Posted by Alan R McDaniel Jr

My "Check Engine" light has been on since 2000. Perhaps I should look into it or find the wire that goes to it.

Alan

Go to AutoZone or Advance Auto to have them read the codes on yer T-100 if it's a 1995 or higher 3.4L or 1994 or higher if it's the 2.7L...

Us 3.0L T-100 folks are outta luck.

xsvtoyz · 02-15-2009, 03:31 PM

if you tap the throttle and it drops clean the throttle body, its probably hanging up. Thats what happened to mine. and the carbon was on the backside.and I didnt get rid of it untill I took the throttle body off.

umpqua123 · 02-17-2009, 08:44 AM

Thanks everyone. At this time, the idle seems to be behaving after a 5 min warmup in the driveway and a drive into town that takes another 10 min. Didn't have to tap the throttle while waiting at a red light to get it to settle down to 750 rpm. It settled on its own, much to my happiness! Hope it lasts for a while...

Thanks for the tips folks. This is an awesome forum!

umpqua123 · 06-12-2009, 04:34 AM

I recently got my clutch/pressure plate replaced on my 97 T-100 4wd with 3.4L engine and for some reason my idle is back to running high after the engine is warm. I can only bring it down to normal when I tap the gas pedal. I need to do this each time I come to a stop light to get it to drop to 800rpm from 1500rpm. I disassembled the throttle body and IAC and cleaned them both out and still have no luck with the high idle. Any suggestions?

BamZipPow · 06-16-2009, 11:28 PM

I'd double check that IAC and throttle body again. Take them both off and give them a good scrubbing. Maybe something is gumming it up again.

Maybe the IAC motor might be weak? Check the electrical connections and see if there is any corrosion or not...