The deep freeze seems to be bringing all sorts of issues out of my truck (94 pickup 4x4, 22re)...as always:) Here's one I'd like to solve: I've got an idle that's always wanting to rev up. Stepping on the brake pedal seems to bring it down (sometimes), but it always and almost immediately revs back up to 2000+ rpms. The only way I can get the idle back down is to engage the clutch in a higher gear. Once it's down at or below 1000 rpms, it usually stays there.

I've heard this could be a dirty throttle body, fuel injector, or a vaccum leak. Well, I've run several cleaners through the system and had no effect, so I'm guessing it's a vaccum leak. Are there likely or more common spots I should check first, and how do I really go about finding the leak? Or, if this doesn't sound like a vaccum leak, what else could be the issue?

Thanks!

Id try to find the vacuum leak first.

Do a visual first. Check for cracks in the intake hose, loose hose clamps, collapsed vacuum lines, dry rotted vacuum lines, etc.

Easiest way to find a leak if you cannot visually see it is to spray something flammable on the hoses and watch for the idle to increase. Easiest thing to use is a bottle of propane, or a can of starting fluid. Just be careful, go slow, and very easy on the fluid. Keep it AWAY from the distributor cap.

Could also be your brake booster. Unplug the vacuum line from the booster, and cap it. See if this helps the idle issue.

You should ensure the idle screw is in where it is actually controlling the idle.
If it is out too far, the idle will creep up.
If the TPS is out of adjustment the idle will creep up.
There are several causes so diagnosing them is step by step process of elimination.
Check the idle screw, vacuum lines and the TPS adjustment, easiest to more difficult.
If you jumper the Diagnosis test like you would when setting the timing, does the engine drop in idle speed?
If not, the TPS is out of adjustment, or needs replacement.
HTH
Danny

I had a similar problem on my 88 4Runner. Took me a while but I did finally discover and correct the problem.
To characterize the problem-
1. Intermittently high, but steady idle (1500-2000 rpms) for over 2 years which resolved by popping the gas pedal.
2. Initially only in summertime, but had progressed to year round.
3. Discovered if the gas was released slowly problem occurred, but if released suddenly, no problem.
4. The throttle assembly could easily (i.e., light digital pressure) be returned to normal when high idle was present.
5. Dashpot ruled out by inspection and using flat bladed screwdriver to push rod going to dashpot diaphragm down during high idle with no effect on rpms.
6. Thorough cleaning of throttle body with throttle/choke cleaner--no effect (but lots of gunk).
Decided it had to be either:
1) weak throttle valve spring--but why not problem all the time?
2) dirty throttle valve rod--why didn't cleaning affect?
3) throttle cable hanging up--made sense with 320,000 miles, sheath may contain gunk increasing friction between cable and sheath, which could be exaggerated in summer by heat expanding metal cable. Fast release of throttle would overcome gunk friction; hence, normal operation when gas pedal popped.

Removed 2 bolts holding throttle cable sheath flange to firewall, and the cable from the throttle assembly. Attached cable lubrication tool to cable end. Sprayed in lubricant until draining at firewall. To my surprise it also drained from undiscovered crack in cable sheath at sharp bend before the flange. Reassembled, took for long drive with many stops--worked fine for 3 days but is now beginning to stick again. Decided to buy a new one; unfortunately Toyota "only" part so I paid $71 from http://www.toyotapartszone.com/1988/78-51-2269-toyota-4runner-accelerator-link.html. If anyone knows of a less expensive source for Toyota "only" parts I would appreciate knowing of it.

www.1sttoyotaparts.com

www.car-part.com for junkyards

Well, a quick update - my idle speed, even when down, was hovering just over 1000 rpms, so I dialed the idle adjusting screw down a quarter turn to reach somewhere in the 850-900 rpm range. I also found a hose connected to the EGR valve that wasn't securely attached.

Third thing I noticed was that by pulling on the throttle cable and releasing slowing, the cable would seem to release all tension, throttle cable pulley would also, but the throttle valve wouldn't fully close. A quick pop of the throttle would resolve this issue. I wondered if I had the same issue as PETDOC with the cable sheath, but after inspecting the cable seems to be moving freely, and I don't see any signs of excessive wearing. I checked the throttle valve spring, and it has plenty of tension and closes fine when moving the throttle valve by hand. It only stuck open when it was moved by the throttle cable pulley. Seemed to be related to the linkage between the throttle cable pulley and the throttle vavle pulley. The linkage was a bit tacky at the ball-in-socket joint connecting to the throttle valve pulley, so I cleaned that up and re-greased.

After these three changes, I haven't had a significant stuck high idle yet, but it's only been a day:)

Question: Is it even possible that the throttle vavle could be stuck slightly open due to a tacky linkage between the throttle cable and throttle valve (knowing that the throttle valve spring is good), or is it soley a vacuum leak that is forcing the throttle valve to stay slightly open?

Sounds like the throttle body is dirty inside and the butterfly is getting stuck.
I would pull the air tube and wipe the bore of the throttle body out real good. Use Seafoam and spray the inside of the intake and let it sit. Then start it up.
I pull a vacuum line to let the Seafoam get sucked into the intake while it is running to help clean things up.

Yeah, I'm starting to think that too. After a long drive last night, the creeping idle returned consistently. I'll clean it out tonight...