idle issue

jayson161 · 12-13-2004, 08:40 PM

the last two days my truck has had a funny idle problem. it doesnt do it all the time just random places where i happen to be sitting at a red light or something. it will just drop in idle real low then pick back up and drop again then it will be fine. could this be a fuel filter or air filter problem?

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ChickenLover · 12-13-2004, 08:43 PM

When was the last time you cleaned your throttle body?

jayson161 · 12-13-2004, 08:44 PM

havent in awhile, and i just saw the thread right below mine where someone asked the same question. i'll look into that tomorrow.

Jake94 · 12-13-2004, 08:48 PM

Words of wizdom from 4crawler:

--------------------------------------------------------------------------
Your idle speed is too high, plain and simple. Here's a Question and Answer from a recent TLCA Toyota Trails "Truck Tech" column:

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.

ChickenLover · 12-13-2004, 08:50 PM

Might as well change the fuel filter too. I noticed an improvement when I did mine a while back. But definately check out that throttle body. Not sure which engine you have but if it's the 3.0, that driver side valve breather sure pumps a load of oil into your throttle body.

jayson161 · 12-13-2004, 08:57 PM

i have the 22r-e, i wonder if there could be a leak in the brakes. i just had a sas done so there was work on my front brakes. but yeah i'll swap the fuel filter and clean my air filter to start with.

12-13-2004, 08:43 PM	#2 (permalink)
ChickenLover Registered User Join Date: Apr 2004 Location: NV Posts: 2,583	When was the last time you cleaned your throttle body? __________________ 95 4Runner, 3VZE , 141k, 4WD, Auto. (Head gaskets replaced at 106k)

12-13-2004, 08:44 PM	#3 (permalink)
jayson161 Registered User Join Date: Aug 2003 Location: washington Posts: 137	havent in awhile, and i just saw the thread right below mine where someone asked the same question. i'll look into that tomorrow. __________________ SFA 1994 toyota pickup 4" front marlin springs/4" rear marlin springs/1.5" rear shackles/5.29 gears/aussie locker/35x12.50 ssr's/15x10 rock crawlers/ARB Bull Bar/Warn M8000 winch/KC slim lites/Bushwacker extenda fender flares/ARB Safari Snorkel---

12-13-2004, 08:48 PM	#4 (permalink)
Jake94 Contributing Member Join Date: Jan 2004 Location: N39 32.872 W104 58.755 Posts: 232	Words of wizdom from 4crawler: -------------------------------------------------------------------------- Your idle speed is too high, plain and simple. Here's a Question and Answer from a recent TLCA Toyota Trails "Truck Tech" column: 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. Last edited by Jake94; 12-13-2004 at 09:03 PM.

12-13-2004, 08:50 PM	#5 (permalink)
ChickenLover Registered User Join Date: Apr 2004 Location: NV Posts: 2,583	Might as well change the fuel filter too. I noticed an improvement when I did mine a while back. But definately check out that throttle body. Not sure which engine you have but if it's the 3.0, that driver side valve breather sure pumps a load of oil into your throttle body. __________________ 95 4Runner, 3VZE , 141k, 4WD, Auto. (Head gaskets replaced at 106k) Last edited by ChickenLover; 12-13-2004 at 08:53 PM.

12-13-2004, 08:57 PM	#6 (permalink)
jayson161 Registered User Join Date: Aug 2003 Location: washington Posts: 137	i have the 22r-e, i wonder if there could be a leak in the brakes. i just had a sas done so there was work on my front brakes. but yeah i'll swap the fuel filter and clean my air filter to start with. __________________ SFA 1994 toyota pickup 4" front marlin springs/4" rear marlin springs/1.5" rear shackles/5.29 gears/aussie locker/35x12.50 ssr's/15x10 rock crawlers/ARB Bull Bar/Warn M8000 winch/KC slim lites/Bushwacker extenda fender flares/ARB Safari Snorkel---

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