Surging idle when brake pedal is applied
03-05-2010, 06:21 PM
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Surging idle when brake pedal is applied
Hey everyone. Ive got a 94 pickup 22re reg cab 4x4. I just recently had the motor rebuilt and the motor runs great. There is only one issue: When i apply the brake pedal, the engine will lope like it is going to stall. When i take my foot off the brake pedal, the motor will be fine. I pulled the fuse for the tail lights, and i try applying the brake pedal again, and the idle is fine, no surging idle.
Does anybody know whats going on here?
Does anybody know whats going on here?
03-06-2010, 07:19 AM
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I think i do have to check my adjustment on the idle, ill check that
03-06-2010, 07:51 AM
#7
X3, and the explanation of why is below:
- http://www.4crawler.com/4x4/TLCA_Tru...ech.04.09.html
- http://www.4crawler.com/4x4/TLCA_Tru...ech.04.09.html
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03-06-2010, 01:07 PM
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X3, and the explanation of why is below:
- http://www.4crawler.com/4x4/TLCA_Tru...ech.04.09.html
- http://www.4crawler.com/4x4/TLCA_Tru...ech.04.09.html
Crazy, I would have never suspected! Thanks for the info!
03-06-2010, 06:56 PM
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06-23-2013, 12:36 PM
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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).
i love that link man it saved my ass... thx a bunch!
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).
i love that link man it saved my ass... thx a bunch!
08-01-2016, 06:08 PM
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Ok, so I have read through as many threads on this as I can find and I have been unable to diagnose this problem correctly. I have a 1989 Toyota Pickup 3.0L V6 4WD. For reference, as might be applicable to diagnosing this problem, the following are some of the repairs and maintenance that I have completed since I bought the pickup about 6 months ago:
Timing belt
Replaced Radiator
Replaced BVS (Bimetal Vacuum Switch, coolant temp operated)
Cleaned the throttle body
Replaced Fuel Injectors
Replaced several coolant bypass hoses and fuel vaccume lines; and visually inspected pretty much every vaccume/bypass hose on the vehicle since they have become accessible during the other maintenance.
Removed AC pressure line, and AC Radiator. (the system had no pressure, the pump was non functional, and I do not plan on bringing it back to functioning condition)
Starting a few months back, after completing some of this work on the engine, I started to notice this surging idle happening when the brake was applied. Based on the link provided in one of the links above, I adjusted the idle speed down (all the way down infact), and this appeared to do the trick ..... initially. However, then I started noticing this happening again, did some more reading on the threads, and got one of the Lisle No Spill Funnels to burp the cooling sustem. I have done that now, and am feeling confident about not having air in the cooling system. However, I still have the surging idle while braking, with no change to how it was happening prior to burping the system. The following are the circumstances under which it seems to want to surge. It only surges now in the morning time, not when it first turns on and is warming up, but after it appears to have reached operating temperature, between 5-20 minutes after startup. I live in Northern CA, and the outside temperature in the mornings around 8 AM (summertime) are 70-80 degrees. When I get off from work in the evenings, temperatures usually are in the 95-105 degree range, and the surging DOES NOT occur.
Seems odd to me just how specific of circumstances this seems to happen, and I hope it can help diagnose what is causing this.
Fyi, the following link posted above doesn't appear to work anymore (the web address seems to have changed)
http://www.geocities.com/toyotashawn/bizzareidle.html
Any ideas for what might be causing this would be appreciated.
Timing belt
Replaced Radiator
Replaced BVS (Bimetal Vacuum Switch, coolant temp operated)
Cleaned the throttle body
Replaced Fuel Injectors
Replaced several coolant bypass hoses and fuel vaccume lines; and visually inspected pretty much every vaccume/bypass hose on the vehicle since they have become accessible during the other maintenance.
Removed AC pressure line, and AC Radiator. (the system had no pressure, the pump was non functional, and I do not plan on bringing it back to functioning condition)
Starting a few months back, after completing some of this work on the engine, I started to notice this surging idle happening when the brake was applied. Based on the link provided in one of the links above, I adjusted the idle speed down (all the way down infact), and this appeared to do the trick ..... initially. However, then I started noticing this happening again, did some more reading on the threads, and got one of the Lisle No Spill Funnels to burp the cooling sustem. I have done that now, and am feeling confident about not having air in the cooling system. However, I still have the surging idle while braking, with no change to how it was happening prior to burping the system. The following are the circumstances under which it seems to want to surge. It only surges now in the morning time, not when it first turns on and is warming up, but after it appears to have reached operating temperature, between 5-20 minutes after startup. I live in Northern CA, and the outside temperature in the mornings around 8 AM (summertime) are 70-80 degrees. When I get off from work in the evenings, temperatures usually are in the 95-105 degree range, and the surging DOES NOT occur.
Seems odd to me just how specific of circumstances this seems to happen, and I hope it can help diagnose what is causing this.
Fyi, the following link posted above doesn't appear to work anymore (the web address seems to have changed)
http://www.geocities.com/toyotashawn/bizzareidle.html
Any ideas for what might be causing this would be appreciated.
10-25-2020, 08:46 AM
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4 years to late but...
Ok, so I have read through as many threads on this as I can find and I have been unable to diagnose this problem correctly. I have a 1989 Toyota Pickup 3.0L V6 4WD. For reference, as might be applicable to diagnosing this problem, the following are some of the repairs and maintenance that I have completed since I bought the pickup about 6 months ago:
Timing belt
Replaced Radiator
Replaced BVS (Bimetal Vacuum Switch, coolant temp operated)
Cleaned the throttle body
Replaced Fuel Injectors
Replaced several coolant bypass hoses and fuel vaccume lines; and visually inspected pretty much every vaccume/bypass hose on the vehicle since they have become accessible during the other maintenance.
Removed AC pressure line, and AC Radiator. (the system had no pressure, the pump was non functional, and I do not plan on bringing it back to functioning condition)
Starting a few months back, after completing some of this work on the engine, I started to notice this surging idle happening when the brake was applied. Based on the link provided in one of the links above, I adjusted the idle speed down (all the way down infact), and this appeared to do the trick ..... initially. However, then I started noticing this happening again, did some more reading on the threads, and got one of the Lisle No Spill Funnels to burp the cooling sustem. I have done that now, and am feeling confident about not having air in the cooling system. However, I still have the surging idle while braking, with no change to how it was happening prior to burping the system. The following are the circumstances under which it seems to want to surge. It only surges now in the morning time, not when it first turns on and is warming up, but after it appears to have reached operating temperature, between 5-20 minutes after startup. I live in Northern CA, and the outside temperature in the mornings around 8 AM (summertime) are 70-80 degrees. When I get off from work in the evenings, temperatures usually are in the 95-105 degree range, and the surging DOES NOT occur.
Seems odd to me just how specific of circumstances this seems to happen, and I hope it can help diagnose what is causing this.
Fyi, the following link posted above doesn't appear to work anymore (the web address seems to have changed)
http://www.geocities.com/toyotashawn/bizzareidle.html
Any ideas for what might be causing this would be appreciated.
Timing belt
Replaced Radiator
Replaced BVS (Bimetal Vacuum Switch, coolant temp operated)
Cleaned the throttle body
Replaced Fuel Injectors
Replaced several coolant bypass hoses and fuel vaccume lines; and visually inspected pretty much every vaccume/bypass hose on the vehicle since they have become accessible during the other maintenance.
Removed AC pressure line, and AC Radiator. (the system had no pressure, the pump was non functional, and I do not plan on bringing it back to functioning condition)
Starting a few months back, after completing some of this work on the engine, I started to notice this surging idle happening when the brake was applied. Based on the link provided in one of the links above, I adjusted the idle speed down (all the way down infact), and this appeared to do the trick ..... initially. However, then I started noticing this happening again, did some more reading on the threads, and got one of the Lisle No Spill Funnels to burp the cooling sustem. I have done that now, and am feeling confident about not having air in the cooling system. However, I still have the surging idle while braking, with no change to how it was happening prior to burping the system. The following are the circumstances under which it seems to want to surge. It only surges now in the morning time, not when it first turns on and is warming up, but after it appears to have reached operating temperature, between 5-20 minutes after startup. I live in Northern CA, and the outside temperature in the mornings around 8 AM (summertime) are 70-80 degrees. When I get off from work in the evenings, temperatures usually are in the 95-105 degree range, and the surging DOES NOT occur.
Seems odd to me just how specific of circumstances this seems to happen, and I hope it can help diagnose what is causing this.
Fyi, the following link posted above doesn't appear to work anymore (the web address seems to have changed)
http://www.geocities.com/toyotashawn/bizzareidle.html
Any ideas for what might be causing this would be appreciated.
the ecu has a redundancy in it that if the idle is above 1000 rpm it will cut the fuel injectors off and on causing the idle. I am super glad I found this before I went and replaced the brake booster. It just didn’t make sense that the booster had a leak when cold and after warm up it went away. The idle on my warm engine is 800 but when that cold start injector is running it’s around 1200. This post is for the people that have looked everywhere and can’t find the answer. Answer is it is normal and if you want it to stop, allow the truck to warm up!
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