1991 Toyota pickup 4cyl, 5spd, after complete warm up it idles a little high. Then when you step on the brake pedal the idle goes down and the engine surges up and down. I temporarily fixed the symptom by adding a return spring to the throttle.
1990 22re same problem surge when pedal was depressed thought it was booster or check valve still didnt fix it i even put a brand new booster on it just to make sure still no fix it finnally went away on its own for about a month now it does it just sitting at an idle with out the brake pedal depressed traced all vaccum lines no problem there and still have no clue
The problem went away when I put the truck into 4-wheel drive. A couple years ago a mechanic replaced the clutch, but didn't reconnect the light which comes on when in 4-wheel drive. Now the surging doesn't go away when I shift it into 4w drive. I'm wondering if there's a short between the 4w drive and an idle circuit. I'm going to try disconnecting the brake light connection at the pedal and see whether that makes a difference.
idle control vavle most likely the problem
i know this is an old post but i had problem with engine surge when brake depressed and everyone keeps saying iac valve, idle too high or timing issue etc... none of that was a problem. remove air screw on throttle body, wrap 4-5x with teflon tape adjust to approx 1 turn out from bottom. problem solved. mine was surging at all rpm, adjusted screw fixed that but then was surging when brake applied, adjusted screw down a bit more and problem resolved for cost of teflon tape. hope this helps!!
i know this is an old post but i had problem with engine surge when brake depressed and everyone keeps saying iac valve, idle too high or timing issue etc... none of that was a problem. remove air screw on throttle body, wrap 4-5x with teflon tape adjust to approx 1 turn out from bottom. problem solved. mine was surging at all rpm, adjusted screw fixed that but then was surging when brake applied, adjusted screw down a bit more and problem resolved for cost of teflon tape. hope this helps!!
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You have a leak in one of your vacuum lines or circuits.
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I Thought it was the brake booster, but i disconnected the vacuum line and plugged it. I started the truck and with a warmed up engine and tried the brake peddle again. It didn't fix the problem, and I'm not sure what else would cause the surging when the brake peddle is depressed. Anybody have other ideas?
i have a 1990 pickup that used to surge when the brake pedal was depressed then it when away for about a month it just came back about a week ago now it does it just sitting at an ide speed with or without the peddal depressed ive checked everything new booster new check valve traced all vaccum lines and still have no clue
I had the same problem, It will be an electrical issue with the brake light switch. Check the light bulbs and the wiring under the bed. Or possible the brake light switch shorting out. I had this problem for months before I figured it out.
i have a 1989 Toy 4cly pickup that surges when the brake pedal was depressed then it when away for about a month it came back about 9 week ago now it does it just sitting at an ide speed when it's cold 45 outside with or without the peddal depressed I've checked everything new booster new check valve traced all vaccum lines and still have no clue
i had the same problem and thought it was a vacuum leak. i disconnected everything the same as you did and no change a friend changed the idle control vavle and that took care of the problem. try that
engine starts easily, has high idle.then surges between high and low idle. diagnosis code 12 shows in diagnosis, but runs normally at higher engine speeds
Engine surges at idle why?
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