Surging Idle

I've had problems with my truck's idle surging when at a full stop. It idles at 1000rpm for about 5 secs then goes to 1200rpm for about 2 secs then back down, etc, etc. It seems to be an intermitent problem but it mainly happens in cold weather. One thing I noticed last night is that the idle surges happens when I stop and have the brake pedal depressed, as soon as I let go of the brakes, rpm's go up to about 1500 rpm and the surging between 1-1.2K rpms stops. Could it be a vacuum problem in the break booster?

Truck: 92 xtra cab, 22re, 4x4, 190,000 miles

Thanks in advance,

Meatloaf

I'm having the same problem with my '94 22R-E. I asked about it on Yotatech, but everyone just said that it's because the idle is adjusted too high. That's not the case. Also there was a post on Pirate yesterday by somebody else with a '94 who had the same problem. Everyone there said the same thing; idle is adjusted too high. Mine is turned all the way down right now just to see if it made a difference.

The reason the idle drops when you are on the brake is because there is a vacuum line attached to the brake booster which cuts fuel to the injectors. It does this so that the idle will drop down when you are slowing down, like coming to a stop sign, etc., and it saves gas while you're just idling by keeping the RPMs down.

There is another system that bumps up the idle speed when the engine is cold. My thought is that this system is somehow not shutting off once the engine is warm, so it and the fuel cut off are working against each other, causing the idle to surge up and down.

If I can't get mine figured out by this weekend I'm taking it in to the shop to see if they can figure it out.

All fuel delivery is controlled electronically by the TPS, o2 sensor, and other sensors providing heat/air related information. You are correct in part that the idle goes down when decelerating but that is more of a function of speed vs TPS position i.e. closed with 0 ohms of resistance. Surging idles have more to do with faulty input signals from sensors. There are many posts on the web about this as it is a common thing with the fuel delivery system of Toyotas.

Have you cleaned your throttle body lately i.e. made sure that the idle passage is clean and that the throttle plate is seating fully? Easy thing to do and really improves idle.

By the way, in the FSM, it states that the Coolant Temp sensor is the 1st thing to check when idle is low or high. It is the second thing to check if starting is hard when cold or hot.

Good info. Thanks. I'm gonna try to work on it tomorrow.

Yes, good info...thanks...I've got a Hanyes manual, see if I can find this info here...

Thanks,
Meatloaf

Mine surges really badly now, only at an idle, with my foot on the brake, and the AC is on. If I turn the AC off, it's fine. I haven't had any time to look into it, just wondering if you have any ideas. My TB is very clean, as is the entire intake, I had it all off the truck back in July.

KLF:

See this:

http://www.yotatech.com/showthread.php?t=67437&highlight=ac+idle

High Idle

Hi
My 1989 with 22RE had a high idle condition that was very difficult to solve. The solution was the replacement of the auxilary air valve ( I think thats what the dealer calls it). It is located under the throttle body and has two coolant hoses going to it. It bolts to the throttle body. It is there to bypass air around the throttle plate when the engine is cold. As the coolant heats up a wax pellet inside will soften and allow the air passage to close. This will lower your cold start idle. This fails and constantly allows air to bypass the throttle plate. I believe it is not repairable.
To confirm if this is your problem allow the engine to fully warm up. Shut the engine off. Pull the air inlet hose to the throttle body and look for a hole, about 1/4 inch in diameter ,at the bottom in front of the throttle plate. Clean the area of oil. Cover this with duct tape. Be sure the duct tape is secure and will not get sucked into the engine. Start the engine and if the idle has dropped the aux air valve is defective.

good luck

fuel pressure regulator?

3BTLC said:

The solution was the replacement of the auxilary air valve ( I think thats what the dealer calls it). It . . . has two coolant hoses going to it. . . This fails and constantly allows air to bypass the throttle plate. I believe it is not repairable.

Click to expand...

Turns out that was the problem on my truck. One of the passages was clogged up and coolant couldn't flow through. It's cleaned out now and running fine.

3BTLC said:

To confirm if this is your problem allow the engine to fully warm up. Shut the engine off. Pull the air inlet hose to the throttle body and look for a hole, about 1/4 inch in diameter ,at the bottom in front of the throttle plate. Clean the area of oil. Cover this with duct tape. Be sure the duct tape is secure and will not get sucked into the engine. Start the engine and if the idle has dropped the aux air valve is defective.

Click to expand...

This method worked to diagnose my truck. When I first taped over the hole, the engine wouldn't start. Since the idle screw had been turned all the way in (I found that as part of another diagnostic routine) I dialed the idle screw out a few turns and the engine cranked right up. I adjusted the idle speed to 800 and it holds steady now, whether the brake pedal is pressed or not. My engine idle was loping both with and without the brake pedal depressed.

My question now is - one or more people seem to have successfully cleaned out the valve. Is there a way to tell if the valve is plugged/clogged without dismantling the entire throttle body? I went took a peek at things and noticed the coolant hoses going in and out of the auxiliary air valve were cool, while the main radiator hoses were warm - would this indicate the valve is plugged/clogged somehow?

Or, if I have to replace the auxiliary air valve - do these things really cost upwards of $200?

If I'm going to take the whole thing apart, I'd rather make sure I fix it ... surely I'd rather do the cheap fix and clean out the valve, but if I need to replace it I'll do that instead.

Thanks!

figured out the fix for my truck

Not that anyone has read this post since my last reply, but it could help a frustrated 22re owner trying to find an answer.

My idle was loping as described by many on different sites. The tape over the hole in the throttle body worked, but is not a permanent solution.

I removed the AAV, soaked it in cleaner, blew out the passages with compressed air put the AAV back on. No luck.

I thought the AAV was bad, so I bought a new one. I got a decent deal on one via Amazon.com. It was about 50% less expensive than from the dealer.

However, the new AAV didn't solve the problem. That made me think the problem has to be somewhere else in the AAV system. Early on I remember thinking the upper hose that comes from near the thermostat was awfully cold when it should be warm. After the new AAV didn't solve the problem, I started investigating there.

I took off the hose and poked a small spray straw (like the one you get with WD-40 or throttle body cleaner). The straw didn't go in very far and I thought it was odd.

I didn't get around to doing anything until today, when I replaced the thermostat, thinking it was bad and possibly affecting the situation. It would also get me another look at that port that leads to the AAV.

Sure enough - I had a major blockage.



(more pictures and sizes)

Stuck in the port, or whatever you want to call it, is some sort of soft rubber gasket-like material. And I have no idea what it's doing there or how it got there! I can only imagine it has been there for some time.

I removed the offending material, cleaned everything up, reassembled and everything runs perfectly now.

I'm curious if BeaterToyota had a similar blockage:

Turns out that was the problem on my truck. One of the passages was clogged up and coolant couldn't flow through. It's cleaned out now and running fine.

Click to expand...

If it is anything like what I found, it would have been nice if they'd given more information!!! Hopefully this will help someone possibly in the future if they have the loping idle problem and has already ruled other things out.

If so, or even regardless, it is always nice when people share more specific information. If BeaterToyota ever reads this, I am curious if their blockage was the same place and similar material.

For those with this problem: Your first step is to cover that hole in the throttle body. If that "fixes" the problem - the solution is not any TPS issues, or vacuum leaks, or snipping wires as a bunch of wingnuts on other forums have suggested. If covering the hole changes things, it should be obvious that either the AAV is bad, or something in the AAV system is not functioning properly.

Steve

Nice detective work!

Many thanks Sogwo - I had the exact same symptoms (idle surging once the engine was warm) and just as you found, the fitting on the thermostat housing that goes to the throttle body was clogged. Cleaning it out with a metal rod fixed the idle problem. You saved me a lot of work and I appreciate your description and photos! -K

that gives me some thing to look at on mine since i have had this problem.