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86-95 Trucks & 4Runners 2nd/3rd gen pickups, and 1st/2nd gen 4Runners with IFS

idle problem when on brakes

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Old Oct 16, 2009 | 02:25 PM
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idle problem when on brakes

this problem started when my brake lights went out, swapped the bulbs, nothing, swapped the fuse and wa-la,

but now the truck idles weird when im not the brakes, when its hot itl idle at 1500, when im on the brakes itll idle from 1200-700 then kicks the rpms back up (EXTREMELY annoying)

tryed messing with it and the guy that had the truck before my seemed to jump the A/M tach right into the ign fuse, first time i messed with it the problem went away, then came back maybe 20 mins later, the problem seems to come and go as it pleases, but once it comes itll stay for the rest of the day

at this point it seems no matter what i do with the tach the problem still presists
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Old Oct 16, 2009 | 03:06 PM
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re-set your idle, its idleing too high and when the brakes are applied the ECU cuts fuel to the injectors causing it to idle down, then it jumps back up, reset per FSM i think its like 750 or somethin?
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Old Oct 17, 2009 | 04:59 AM
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how do i do that?
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Old Oct 17, 2009 | 05:45 AM
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theres an idle screw on the side of the TB, also theres a link to the FSM (Factory Service Manual) that gives you step by step instructions on how to idle the vehicle with pictures
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Old Oct 17, 2009 | 03:15 PM
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so my battery went today, replaced it and noticed my battery gauge is only reading 11.5V, idle problem went away but gotta wait till tuesday before i can get an alternator...
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Old Oct 17, 2009 | 04:11 PM
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?? thats weird, havent heard that one yet...every thread ive come across and some stickied stuff over at pirate, with this prob listed was the idle set too high, glad you figured it out tho..have fun with the alt!
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Old Oct 17, 2009 | 04:42 PM
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haha is the alt a pita? i think the problem ended up being that the battery couldnt power the brake lights and engine at the same time since the alt was shot... i never ran the car at night so headlights were never an issue
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Old Oct 17, 2009 | 05:05 PM
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did a search and found this
https://www.yotatech.com/forums/f131...citing-131679/
maybe its just a fuse? idk since my 22re fuse box is different than the 3.0
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Old Oct 17, 2009 | 05:16 PM
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did you get your alt tested in the truck? the next step is to get it tested out of the truck if you really wanna be sure its the alt, its not that big a deal just power steering lines and other stuff is in the way, you have to flip it upside down left and do a barrel roll to get it out and in lmao
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Old Oct 17, 2009 | 05:26 PM
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lmao sounds good, looks tight but thats never stopped me before, didnt get it tested outside the truck but i dont wanna pull it out and have to find out its bad and not have a good one to put back in... catch 22

EDIT: tried messing with the truck and the battery light does not come on when the accessories are on before i start the truck, so it could easily be the same problem as the guy from the other thread

Last edited by greatskiiiier; Oct 17, 2009 at 05:28 PM.
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Old Oct 17, 2009 | 05:34 PM
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...... if your hitting your brakes and your idle goes down then your brake booster is defective and leaking or the vac line going to your brake booster is leaking. Your idle is wrong and should not be that high. Anything bellow 1000 is good but factory idle is about 750-800. Fix all vac leaks and get engine mechanicly sound before adjusting idle. You need to give us a bit more info on your charging system prob for us to help..... Your battery should read 12v if its lower than that then the battery is trash for your alternator is not putting out enough. Get it tested see if its good make sure its the right alternator for your truck.

Last edited by Kiroshu; Oct 17, 2009 at 05:37 PM.
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Old Oct 18, 2009 | 06:34 AM
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Originally Posted by Kiroshu
...... if your hitting your brakes and your idle goes down then your brake booster is defective and leaking or the vac line going to your brake booster is leaking. Your idle is wrong and should not be that high. Anything bellow 1000 is good but factory idle is about 750-800. Fix all vac leaks and get engine mechanicly sound before adjusting idle. You need to give us a bit more info on your charging system prob for us to help..... Your battery should read 12v if its lower than that then the battery is trash for your alternator is not putting out enough. Get it tested see if its good make sure its the right alternator for your truck.
it only started happening after i replaced a fuse and now that theres a new battery in there it doesnt happen anymore

i believe the alt and batt were going out and since i never drove the car at night (never turning on the headlights) the problem was that when i did hit the brakes it was drawing too much power from the ign resulting in a loss of spark which the engine compensated for by opening the throttle
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Old Oct 18, 2009 | 09:06 AM
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Originally Posted by Kiroshu
...... if your hitting your brakes and your idle goes down then your brake booster is defective and leaking or the vac line going to your brake booster is leaking. Your idle is wrong and should not be that high. Anything bellow 1000 is good but factory idle is about 750-800. Fix all vac leaks and get engine mechanicly sound before adjusting idle. You need to give us a bit more info on your charging system prob for us to help..... Your battery should read 12v if its lower than that then the battery is trash for your alternator is not putting out enough. Get it tested see if its good make sure its the right alternator for your truck.
charging system problem is fixed (see my other thread if you want details)

idle problem went away for about 15 mins of driving as well, thought problem was fixed, but when i hit the brakes the idle would drop to about 700 then rest at 900 while the brakes were held

then it would jump from 700-900 the whole time i was on the brakes- could it be that my valve tick is pulling some vaccum? im ganna mess with some of the hoses after lunch to see if thats the problem too
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