wrenchtech

My 1989 4runner 22RE just started idling faster and surging when the brake is applied. This happened last winter, but went away with the warmer weather. I disconnected the vacuum line to the brake booster and plugged it to test for a vacuum leak; nothing changed. So I'm assuming that the stop light circuit, which also feeds into the ECU, is the trigger for the surging. But why?

I am thinking I will have to start a process of elimination. Suspect parts include the throttle position sensor (TPS), the air flow meter (AFM), Auxiliary Air Valve and various temperature sensors.

Well considered help is sought and welcomed. -- Matt

Erik Beeman

Make sure your battery is well connected and the ground is attached and clean.

Don't ask me how I know.....

wrenchtech

Maybe I could clean up the battery terminals (which are already in good shape) and make some temporary ground wires between the chassis and the engine and the battery. The brake light "trigger" means something. I wish I knew what though :-) -- Matt

cody o

Hello! First time here; just joined because I may have a solution for you. I have a 94 p/u 22re that had a similar problem: when the a/c was on, the engine idle would surge repeatedly while the brake was depressed. Turns out the main idle speed and the a/c fast idle speed adjustments weren't set properly. The change in vacuum when you press the brake causes this. Try setting all your idle adjustments according to the book.

wrenchtech

I think I've narrowed this problem down. I cleaned all my electrical connections and made some extra ground wires to the body and the motor for testing purposes. Nothing changed.

This morning I started the truck up in neutral with the wheels blocked. The outside temperature was about 60 deg F. It started fine and had a good cold idle. As it warmed up, in about 5 min, it began surging at idle. It definitely sounded like it was idling fast enough to be bumping up against the computer fuel cut off. What this means is that when the computer senses that the engine is at normal operating temps and idling too fast it briefly turns off the fuel until the RPM's come back down, but because something else is wrong the idle just kicks right up as soon as he fuel comes back on. This immediately made me suspect the auxiliary air valve (AAV), which is located in the base of the throttle body. Touching the outside of the housing it felt cool. The thermostat housing was hot, but the AAV coolant pipes were not. I then turned off the motor and got a propane torch. With the torch I carefully heated the AAV housing part of the throttle body. Then I started the truck again and BINGO! the idle was now at around 600 RPMs and steady. In another minute or two the idle started to climb. It climbed until it banged up against the fuel cut whereupon it started too surge again.

Conclusion: Heated coolant is not circulating properly through the AAV. It may be as simple as a bad thermostat. There has been some weirdness which causes the temperature gauge to indicate that the engine is on the verge of overheating not long after I start driving and then suddenly the temp gauge drops to the normal zone. It's like the thermostat is sticky, not opening until the engine is at maybe 220F, but then functioning normally after the initial difficulty. When I bought this truck the AAV was malfunctioning because the internal coolant passage was plugged up tight. I had to disassemble the AAV to clear the blockage. Maybe it's blocked again?

In any case I'm going to replace the thermostat and check the AAV coolant passage -- Matt

I almost forgot: The surge also gets worse when brake is applied. This is not a vacuum problem in my case. If I remove the brake booster vacuum line, and plug it, the engine still surges when I apply the brake. Even the slightest movement of the brake pedal triggers the brake light switch. I'm pretty sure it's related to the brake light circuit, which is also connected to the ECU.

Junkers88

If you pull the AAV (or Idle Air Control Valve IACV as it is sometimes called) to clean it then you really need to do the rest of us a favor and snap some pictures and do a write up on it. I have a similar high idle issue when the rig is cold and know that it's the IACV, I just don't know how to clean it and since I only have one vehicle I kind of need to be able to get it all back together for work.

Ok your surging when the brakes are applied is due to your high idle. When the brakes are applied the ECU cuts the fuel so the rig will idle, if the idle is set too high then the ECU will sense this and cut the fuel again..... idle high, ECU cuts fuel, idle high, ECU cuts fuel. The result is a surge. I know because I've had this happen on two vehicles. Get your idle set to factory specs and the surge will go away. If getting the idle back down to where you want it requires you to replace/clean the AAV/IACV then pretty please do a write up with pictures and instructions.

myyota

The water passages going to the idle air valve can plug up with rust and crap and not allow the water to properly flow through the valve, i would recomend that you remove the air valve and coolant lines going to it and clean them out, that will probably fix the problem your having.

wrenchtech

Someone PM'd me on this to see if I had found a solution to my problem. It was indeed the Auxillary Air Valve (AAV), which is on the side of the throttlebody. There is a coolant passage through there that heats something that opens and closes an air passage in the throttlebody to give the engine a fast idle when the engine is cold. If you don't have coolant flow the AAV stays too cold to come off of high idle. When the engine is warm and the AAV is cold the engine can idle so fast, 2000 RPM+, that the Engine Computer tries to cut the fuel. It cuts and then idles up and then cuts again, over and over. So it's surging like that. The coolant passage in mine was so plugged that I had to drill out a plug in the body to get to the clogged area. After i put it back together I had a nice running 22RE, which can be a mighty fine thing, If you're a t4x4 nut like me. -- Matt

MortonPhotographic

All that talk of rust and plugged AAV just clicked in my brain... I am having the same problems above and my truck sat for year with water in the cylinders and who knows where else--it was so bad I had to replace the block. So it makes sense that my AAV is rusted and plugged up even though I have gone through everything else.

Thanks for the posts everyone!

91muddog

just want to say thanks to everyone for all the help in this thread, i am having the name issue and have narrowed it down to this also. ill be tearing into it this weekend, ill post pictures and results also

MortonPhotographic

Took out my AAV today--it wasn't that bad. Worst part was dealing with the radiator fluid.

1) Looked in it and passages were clear.
2) Blew air into it (both water and airways) and it flowed through.
3) Tested impedence and it was like 50 ohms--well within range.

Seriously, this isn't the problem?!?

Then I shook it--the rattle inside was obviously a problem so I opened it up. Turns out the little tab was broken off. Basically the flat metal part turns, but it does not move anything else in the unit and therefore the air section was always blocked off.

http://www.flickr.com/photos/mortonphotographic/6267347168/http://www.flickr.com/photos/mortonphotographic/6267347168/ by http://www.flickr.com/people/mortonphotographic/, on Flickr
This is my pain.

http://www.flickr.com/photos/mortonphotographic/6267347100/http://www.flickr.com/photos/mortonphotographic/6267347100/ by http://www.flickr.com/people/mortonphotographic/, on Flickr
Here is the AAV opened up. That round-ish plastic disc turns when the hot water rotates that flat metal piece. Notice that the flat metal piece will not come in contact with the plastic disc. That is because the little piece at the bottom broke off.

My AAV tested out perfectly, so if you have the idle issues related to it, but yours tests out, open it up and take a look inside. It is just 4 phillips head screws and a rubber gasket (I think) that should re-seal up when you put it back together.

MortonPhotographic

http://www.flickr.com/photos/mortonphotographic/6266823673/http://www.flickr.com/photos/mortonphotographic/6266823673/ by http://www.flickr.com/people/mortonphotographic/, on Flickr
Here is a shot of the Auxiliary Air Valve bolted to the bottom of the intake plenum complete with air and water hoses.

http://www.flickr.com/photos/mortonphotographic/6267347128/http://www.flickr.com/photos/mortonphotographic/6267347128/ by http://www.flickr.com/people/mortonphotographic/, on Flickr
And this is the AAV out of the vehicle. It is Toyota part number 22230-35010 at least for my 1988 4Runner, 22RE, 5 speed, 4X4.

91muddog

Thanks for the info Morton! For sure going to help when i tear into mine. Hopefully tonight!

MortonPhotographic

No problem! I gotta do what little I can to pay back because Yotatech has been a huge help to me!

91muddog

Well, Upon further investigation, my truck doesnt have one haha

Drillin_guy

Yeah this is my problem also. I don't have that style AAV. I do have a black canister deal bolted to the intake with a hose coming from the air filter box. Is that where I should be looking.

Dirt Driver

I have been chasing an inconsistent idle with my truck for a long time. It usually idles low on cold startup unless I blip the A/C on and off, then it idles up until warm like I would expect. At this point I can only figure that my thermostatic idle valve is questionable.

The VSV has also never raised the idle when I have the A/C on. I have to raise it manually with the pedal when stopped for the compressor to come on. I tried cleaning the idle air valve once already and it didn't seem that dirty.

kirkerik

Thanks all. Great info!

TNRabbit

The VSV for the AC can easily be adjusted by hand to idle up when the AC kicks in. It's a bolt-head plastic screw. Very easy to spot.

Dirt Driver

So that's what that thing is.