Surging Idle

meatloaf · 12-21-05, 08:58 AM

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

BeaterToyota · 12-21-05, 04:08 PM

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.

Jukelemon · 12-23-05, 09:23 AM

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.

BeaterToyota · 12-23-05, 08:09 PM

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

meatloaf · 12-23-05, 08:20 PM

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

Thanks,
Meatloaf

KLF · 12-24-05, 08:13 AM

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.

Jukelemon · 01-05-06, 11:42 AM

KLF:

See this:

http://www.yotatech.com/showthread.p...hlight=ac+idle

3BTLC · 01-11-06, 05:16 PM

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

cabron · 01-11-06, 05:42 PM

fuel pressure regulator?

BeaterToyota · 01-19-06, 03:33 PM

Quote:

Originally Posted by 3BTLC

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.

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.

sogowo · 09-07-09, 03:42 PM

Quote:

Originally Posted by 3BTLC

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.

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!