Having troubles with my '89 4Runner - 3.0L V6, Auto, 175K. Idle speed has jumped to ~1600rpm (~1000 in gear) and stays higher than normal while driving and there are occasional stumbles while driving (like fuel or spark has been interrupted momentarily). Sometimes the rpm's drop to 300 or 400 then go back to about 1500 in a repeating cycle. This only happens when in Park or Neutral and I press the brake pedal. The same thing happened once before and I traced this problem to the brake light switch (can't explain what was happening though). I played with several things to correct the high rpm's, including unplugging the cold-start injector, cleaning and resetting the TPS, and resetting timing. Something worked, but only for a couple of weeks. I put match-marks on the TPS body and distributor housing when I finished last time & neither has moved. Anyone got any ideas? Thanks!!!

 

Hey mtnfreak,
I had this problem in my old '91 and I had to cut the brake wire to the ecu and bypass it...here's a link that helped explain it. Once I did it, it stopped. You would need a volt meter to check it if you want to go the route I did...Email me if you got questions.

here's the link from Shawn's site

weird idle

Salue

Keep us posted

 

After reviewing the link posted above, I thought I should comment.

I have seen this happen on only 22RE engines. Which seems strange to me. I have been working at a Toyota Dealer since 91'. One would think that I might have "seen it all". Perhaps thats not the case. So the information I will provide you with is in my experience on the 22RE only, but hopefully can be applied in your case.

I have seen several reasons why the "Rapid Idle Fluctuation" happens. Common to ALL of those reasons was a vacuum leak. A vacuum leak is when you have "unmetered" air entering the engine.

First inspect all your hoses. Look for a hose not connected, or a place a hose isnt connected. Look for a hose routed near something hot, and check to see if it has cracked, and is leaking.

Now I would clean the throttle body. For best results, I would remove the throttle body and clean with carb cleaner and a tooth brush ( not your wifes though ). Clean the butterfly valve and bore really well. No need to disassemble it, just clean it. Re-install the throttle body.

Next I would adjust the ignition timing and idle to specification. If your vehicle is equipted with A/C, adjust the "A/C Idle Up Valve" to 100RPM more then the Base Idle when the A/C is ON.

That should do it. Period.

Sitting here and thinking, I can not think of ANY time I fixed this problem where, had I known at the time, these steps wouldnt have fixed it.

*Tosses in his 2 shinnies*

Jay

 

I too have this problem on my '91 22RE. The engine has a fresh (<500mi) rebuild. I did clean the throttle body, which helped a low idle problem, but then uncovered this problem. I have looked at the vacuum lines many times, but am still trying to figure this one out.


After thinking about it, and looking at some wiring diagrams, I have a thought. Does anyone out there know if a bad or (in my case probably) forgotten grounding of the engine wiring harness cause something like this? After looking at the diagram, I am starting to wonder if I got the grounding point that's under the intake manifold.

 

Sorry it’s taken so long to get back to this, but I’ve been busy. I think I’ve traced the idle problem to a leak in the AS Reed Valve (aka PAIR Valve), but I’m not 100% sure. Does anyone know if this part can be tested without taking it off the engine? I’m pretty sure I’d have to bust the nuts off of the manifold to get it off. I checked and cleaned the TPS again and spent a lot of time moving it micrometers one way or the other to get all of the settings as close to the middle of the range as possible. I checked the throttle body again and couldn’t find anything out of whack. Same for the air intake. Checked all the plugs and wires and they’re fine. Couldn’t find any other vacuum leaks. Plan to replace the cap & rotor this weekend. (FYI one of the local dealers has one (1) Factory Repair Manual left for the ’89 4Runner – only $30. See http://www.longmonttoyota.com/ for contact info.) I may try to do the brake light / ECU bypass just to avoid any future problems. Anyone ever tried bypassing the ~1500 rpm fuel cut itself?

 

Talked this around with a pal.

Hes said hes seen it. He feels the Idle Air Control valve (IAC) is faulty. He said you can test it by covering the holes that go to the IAC inside the throttle bodies bore with duck tape. Be sure that you have it cleaned really well, to insure the duck tape will stay. If the rapid surging goes away, you know your right.

New to me.

Jay

 

So which component is this Idle Air Control Valve? The throttle body has four smaller vacuum connections and a couple of other larger ones.
Looking at the scematic I see that there is an idle-up valve....which is not connected by vacuum to the TB.
The four vacuum lines connect to:
VSV for the pressure regulator. (fuel)?
EGR Vacuum Modulator...x2
Canister...fuel evap I assume

The idle-up valve is connected to another VSV.....is this idle-up valve directly attached to the TB?

My problem seems to go away when I believe the engine is warmest....i.e. after highway driving. Even while driving around, (in this cooler weather) the engine may cool some and the problem re-appears.

It sounds like your (or your friend's) suggestion points in the right direction.

 

Thanks everyone. These intermittant problems are maddening. The idle problem has not returned in 1 1/2 weeks so I've been trying to track down other problems that could cause a high idle. From reading some other posts, it seems that a blocked coolant line to the throttle body could cause high idle. Maybe the recent flush & fill knocked something loose but didn't wash it out and it plugs one of those lines occasionally. Also, my EGR vacuum modulator is bad about every other time I test it - think I'll just replace it since it's not that expensive. The AS Reed Valve / PAIR Valve makes odd noises sometimes too. There is a hissing and clicking noise coming from it - both go away when I remove the small vacuum line. Anyone have any experience with these valves?

 

The IACV is on the bottom side of the throttle body, it has 2 coolant tubes routed to it.

Jay

 

(The AS Reed Valve / PAIR Valve makes odd noises sometimes too. There is a hissing and clicking noise coming from it - both go away when I remove the small vacuum line. Anyone have any experience with these valves?)

I think you may have the same problem I had with these lines after I put mine back together, ended up I had the lines reversed. These are the two smaller vacuum lines paired up that go to one of the valves on top of the valve cover.....I think the forward-most one.

It seems I may have the idling problem fixed.
As time, mileage & carbon deposits added up on my throttle body, the idle adjustment must have been moved up to compensate. After I cleaned the throttle body, there was no need for this compensation. As the adjustment was set to let more air through, this would have raised the idle up into the range of the fuel cut-off limits when you have the brakes depressed. Last night I adjusted the idle down to around 800. Driving to work this morning and back this afternoon, I saw no evidence of the problem at all.

Thanks Jay for your inputs, I think they pushed me hard enough in the right direction.