86 idle problem when brakes are applied
Jan 12, 2012 | 08:13 AM
#1
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86 idle problem when brakes are applied
This problem is making me crazy I have tried everything that i know of. So i bought this 86 22re truck about 2 months ago it had the idle problem when the brakes where applied is would almost turn off. I poked around and found that the booster was bad. I went to pull out a used one replaced it and problem solved. then about a week ago i went to the car cash to clean it up i a had the great idea to give the engine a rise. On the way home form the car wash when i would apply the brakes the RPMs would go down then up, down and up till the were released. I thought is was trapped water somewhere so when i got home i left it on for a while to allow the water to evaporate.
Since then it been doing to same thing, but i have noticed some patterns
. The problem only starts when the engine is hot never when its cold. IT seem to take more running time at night or in the early morning till the idle problem starts. Here's where i need help, could it be the booster? or some sensors? All i know is that it has to do something with the tempaure and the brake booster.
I have check hoses on the EFI to make sure there is no leaks or disconnected
hoses.
well guys any input would help thx
Since then it been doing to same thing, but i have noticed some patterns
. The problem only starts when the engine is hot never when its cold. IT seem to take more running time at night or in the early morning till the idle problem starts. Here's where i need help, could it be the booster? or some sensors? All i know is that it has to do something with the tempaure and the brake booster.
I have check hoses on the EFI to make sure there is no leaks or disconnected
hoses.
well guys any input would help thx
Last edited by DES_YODA; Jan 12, 2012 at 08:15 AM.
Jan 12, 2012 | 08:18 AM
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From: Albany, NY
This may sound dumb, but get your alternator checked, you could have a bad regulator. If your idle drops when you apply the brakes it could mean that your alternator is on it's way out.
All electronics work better when it is cold and especially during the cold start phase when RPMs are higher your alternator is spinning faster.
All electronics work better when it is cold and especially during the cold start phase when RPMs are higher your alternator is spinning faster.
Jan 12, 2012 | 08:29 AM
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This may sound dumb, but get your alternator checked, you could have a bad regulator. If your idle drops when you apply the brakes it could mean that your alternator is on it's way out.
All electronics work better when it is cold and especially during the cold start phase when RPMs are higher your alternator is spinning faster.
All electronics work better when it is cold and especially during the cold start phase when RPMs are higher your alternator is spinning faster.
thx for reply
Jan 12, 2012 | 08:30 AM
#5
Jan 12, 2012 | 08:44 AM
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thx... i tried a search but did find anythingthx guys im going to poke around i'll let know what happens
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Jan 12, 2012 | 10:02 AM
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How does the truck cold start with the brake pedal applied while cranking? How does it hot start with the brake pedal applied while cranking?
If you've confirmed all of the vacuum lines, my guess is that your booster is has a leak to atmosphere in the cabin. You draw in atmospheric pressure from the front of the booster (the part that sticks through into the cabin by the pedal box) through the filter just behind where the booster pushrod clevis connects to the brake pedal. If there is a leak there, you will have a direct path for intake vacuum to leak to atmosphere when the brakes are applied. Depending on the size of the leak, it shouldn't cause a hard pedal either (the normal booster failure symptom).
If your truck starts easily with no brakes and difficult with the brakes applies, the above is likely true. If no difference, than probably not.
One easy thing to confirm - pull your booster check valve and make sure its still one-way flow.
If you've confirmed all of the vacuum lines, my guess is that your booster is has a leak to atmosphere in the cabin. You draw in atmospheric pressure from the front of the booster (the part that sticks through into the cabin by the pedal box) through the filter just behind where the booster pushrod clevis connects to the brake pedal. If there is a leak there, you will have a direct path for intake vacuum to leak to atmosphere when the brakes are applied. Depending on the size of the leak, it shouldn't cause a hard pedal either (the normal booster failure symptom).
If your truck starts easily with no brakes and difficult with the brakes applies, the above is likely true. If no difference, than probably not.
One easy thing to confirm - pull your booster check valve and make sure its still one-way flow.
I did find the problem though,the idle speed was set too high. I lowered it and took it for a dive and anything, no idle problems
thanks everyone!
Jan 14, 2012 | 10:19 AM
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From: Temecula Valley, CA
Yup yup.
If the rpm's are above 1000 or so, the ECU will cut fuel when the brakes are applied. It's a "feature" to help out with "engine braking" and to help reduce emissions... and an annoyance when people don't know about it when tuning their engines.
If the rpm's are above 1000 or so, the ECU will cut fuel when the brakes are applied. It's a "feature" to help out with "engine braking" and to help reduce emissions... and an annoyance when people don't know about it when tuning their engines.
Jan 14, 2012 | 10:57 AM
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