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Surging Idle #535682 12/08/04 04:06 PM
Anonymous
Unregistered
I have a 1989 4x4 22RE, 5 speed. After about 5 minutes of driving, before the engine is fully warm, but after it has warmed up a bit, when you come to a stop the engine idle surges. However, this only happens when your foot is on the brake pedal. If you lift your foot off of the brake pedal, the idle evens out. You don't have to touch the accelerator pedal at all. After the truck is fully warm, this no longer happens. Any clues?

From the Off-Road World
Re: Surging Idle #535683 12/08/04 04:51 PM
Anonymous
Unregistered
I had a similar problem with my 90 toyota 22re. I replaced the throttle body from a parts truck and it went away. The thermosensor under the throttle body is probably getting bad. It has two small coolant lines going to it and it actually bolts to the bottom of the throttle body (tb). It allows more air to pass through the tb on cold start up. Why it comes and goes and does it only with the brake on? Who knows. It is a expensive part from Toyota, you might want to look for a used one. If you do replace it you may have to remove one of the small coolant hoses going to it to get air out of the sensor, I have had it only happen once but it did happen. Good luck.

Re: Surging Idle #535684 12/08/04 05:51 PM
Anonymous
Unregistered

Re: Surging Idle #535685 12/08/04 06:23 PM
Joined: Jan 2004
Posts: 426
G
GeriatricToy Offline
Mudrunner
I've heard a lot of people talk about the brake booster being the culprit of this odd occurance. This happened to me a couple of weeks ago after doing some engine work and the first thing I said was, "Oh Great, now I have to mess with the brakes" <img src="/forums/images/graemlins/zombie.gif" alt="" />. Coincidentally, my idle was a bit off so I adjusted the throttle linkage (tightened it a bit)and the surging idle with the brake pedal engaged phenomenon went away. If my idle hadn't been off then I would have been investigating the brake booster.


2000 Tacoma SR5 - Bone stock 'cept a little bling.
2000 Tacoma SR5 - Bone stock.
Re: Surging Idle #535686 12/08/04 06:23 PM
Joined: Jan 2000
Posts: 12,153
4Crawler Offline
Web Wheeler
*****
Your idle speed is too high, plain and simple. Here's a Question and Answer from a recent TLCA Toyota Trails "Truck Tech" column:

Quote

Q: I have a 94 4wd p/u w/ 22re. My engine runs great, except for when it is idling and I depress the brake pedal. The engine then idles really weird, kind of a strong then weak then strong then weak, so on and so forth. It never cuts out, though, and continues to idle normally when I take my foot off of the brake. I've only noticed this after driving, like at a stoplight.

A: Assuming there are no vacuum leaks, such as in the brake booster, it's likely because your idle speed is set too high. I can exactly duplicate this "problem" in my '85 by bumping up the idle speed to a bit over 1000 RPM and it'll act as described. Turn the idle speed back to normal, and it works fine. It's really not a problem, its supposed to work this way and if everything is set properly, and you won't have the "problem".

Why is this the case? Because the ECU has logic built in that says if you hit the brakes and the engine is turning over 1000-1100 RPM, it'll cut the fuel to the injectors in an attempt to help you stop faster. After all, no sense pumping gas into the engine when you are braking to a stop. So idle rises, fuel is cut, idle falls, fuel restored, idle rises, etc. Turn the idle back to 850-900 RPM where it's supposed to be and it'll get back to normal. Idle speed is adjusted with the large slotted screw atop the throttle body. Turn it in to lower the amount of air passing through the throttle body at idle (and thus lower the idle speed).

If you don't want to do that or it doesn't fix the problem, here's a more drastic fix:
http://www.geocities.com/toyotashawn/bizzareidle.html
Which basically involves cutting the wire that feeds the brake light signal to the ECU. Without that input, the ECU will never know you are braking, so it'll not be able to cut off the fuel injectors.

Re: Surging Idle [Re: 4Crawler] #535687 12/08/04 06:30 PM
Joined: Jan 2004
Posts: 426
G
GeriatricToy Offline
Mudrunner
Ah yes, to add to what 4crawler just said and to not make your issue any worse than it is, I tightened up on my throttle cable because my idle air adjusing screw was turned so far counter-clock-wise to keep my idle up, that I don't think I had much thread left and the fear of this thing backing itself all the way out wasn't pretty.


2000 Tacoma SR5 - Bone stock 'cept a little bling.
2000 Tacoma SR5 - Bone stock.
Re: Surging Idle [Re: GeriatricToy] #535688 12/08/04 10:53 PM
Joined: Dec 2004
Posts: 143
E
eastcoast Offline
Wheeler
i have an idling problem in my 94 22re, have had it for awhile. ive tested the afm and tps, they check out fine, injectors are clicking, valve clearance and timing are spec and i changed the timing chain less than 10k miles ago. plugs wires cap and rotor are all new, i threw on a set of accel wires someone gave me for free as well <img src="/forums/images/graemlins/smile.gif" alt="" />, and new ngk plugs. yet the idle wont stay still, and the brake light is constantly on. i can hear it surging then the fuel cutoff kicks on. when i come to a stop or put it in neutral coasting to a stop, it idles below or around 500 rpm, if i tap the gas itll head back up, but steadily climb and surge off and on. i really want to avoid cutting and splicing the brake light wire at the ecu, i want to find out whats causing it to idle up like that in the first place! im thinking the brake light being on may have something to do with it, but i may be wrong, any ideas appreciated, this is starting to raise the blood pressure, and its getting too cold to be out wrenchin on stuff


'94 X-Cab, EB inside and a few fabbed parts. My wife: "How about you stay on the road?" Me: "I drive a Toyota truck, the road is OPTIONAL!"
Re: Surging Idle [Re: eastcoast] #535689 12/08/04 11:01 PM
Joined: Jan 2000
Posts: 12,153
4Crawler Offline
Web Wheeler
*****
Find out why the brake light is on and fix it. Likely the switch by the brake pedal is mis-adjusted or defective. Test it out, fix or replace it if that is the problem. Then set your idle speed to spec. and it should be fine. Note, the ECU "sees" the same signal that the brake light does, so if the light is on, the ECU "thinks" you are pressing o n the brakes trying to stop. As I noted in my earlier reply, if the engine is above about 1100 RPM and the ECU sees the brakes applied, it assumes you are coming to a stop and shuts off the fuel to the engine to help slow you down.

Re: Surging Idle [Re: 4Crawler] #535690 12/09/04 12:13 AM
Joined: Dec 2004
Posts: 143
E
eastcoast Offline
Wheeler
i tested the switch and the leads to the ecu today and its all in order. the idle speed is turned down slightly below where its supposed be, its not turned up...im at my wits end and i refuse to take it to a mechanic, its not throwing any codes, they can never figure out toyotas anyways, at least around here <img src="/forums/images/graemlins/notooth.gif" alt="" />


'94 X-Cab, EB inside and a few fabbed parts. My wife: "How about you stay on the road?" Me: "I drive a Toyota truck, the road is OPTIONAL!"
Re: Surging Idle [Re: eastcoast] #535691 12/09/04 12:17 AM
Joined: Dec 2004
Posts: 143
E
eastcoast Offline
Wheeler
oh yeah, the parking brake switch tested ok as well, thought id toss that in to rule it out <img src="/forums/images/graemlins/smile.gif" alt="" />


'94 X-Cab, EB inside and a few fabbed parts. My wife: "How about you stay on the road?" Me: "I drive a Toyota truck, the road is OPTIONAL!"
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