1986 Toyota Pickup Idle Surging

1986 TOYOTA PICKUP
4,000 MILES • 4 CYL • 2WD • MANUAL
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JJSJJSVA
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The 22REC engine idles smoothly at approximately 1200RPM with the airconditioner runnings, but when I apply the brakes (to keep it from rolling or what ever), the engine idle surges up and down 0from 800RPM to 1200PRM. When I take my foot of the brake the engine returns back to a smoth 1200RPM.

Nothing else seems to induce this surging- just applying the brakes. I tried high beams on, lights off, turn signals on..etc and no surge, just the brakes.

I did have a new Jasper engine put in during the past winter and I think they didn't hook something up correctly because I didn't have this surge last summer before the new engine.

The AC system is original except for the replaced compressor clutch which blew the fuse. Vent temp when set on recirculating, on a 95 degree day, is 38 degress F.

What is causing this new suring problem.

Thanks,

Joe
Jun 8, 2008 at 9:11 PM
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KHLOW2008
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Hi jjsjjsva,

Check out the brake booster for vacumn leakage.
Jun 9, 2008 at 12:38 PM
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JJSJJSVA
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Vacuum is fine.

Turns out to there is this spring loaded, big nylon bolt, that adjusts into some sort of vacuum housing with a direct line to the A/C VSV.

I unscrewed it during winter trying to cure a rough idle (was a bad spark wire). It sits on top the engine, in middle, between the intake manifold and the valcve cover.

Once I saw the direct vacuum hose going to the A/C VSV I screwed it into about 1/4 out. That seems to have taken care of the problem. Only on a few occasion does it fluctuate and then only form 900 to 1000 RPM. I think it needs a few more turns in and that should do it.

I couldn't find this device in any of my 3 repair manauls and one is the official Toyota shop manual for my truck, so I still don't know its true function.

Thanks for the help.
Jun 11, 2008 at 8:07 PM
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KHLOW2008
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Hi jjsjjsva,

That should be the AC idle up compensater.

Set idling without AC on with idle adjust screw.

Switch on AC and set idling by turning the hex key adjuster.

Your model does not have any ISC or IAC so it need this device.
Jun 12, 2008 at 6:00 AM