Topic: Whats wrong with it?

[sam2145871]

I threw a rod through the block in the first engine in my '91 so I went and put another 22RE in. The problem is that now when I put the breaks on to stop, the truck idles down and then back up and it does that until I release the brake. What could be doing this? Thanks

Marcus

[MiniSimp]

I threw a rod through the block in the first engine in my '91 so I went and put another 22RE in. The problem is that now when I put the breaks on to stop, the truck idles down and then back up and it does that until I release the brake. What could be doing this? Thanks

Marcus

Vacuum line?

[toyotanner]

i think it means theres a leak in your brake booster vaccuum line

[TxFireman]

I agree. If the brake booster has a leak in the diaphram, then it will drop idle & stumble when you hold your foot on the brake while in gear. It will run normal otherwise. You'll often also hear an "airy" sound when you step on the brake.. but that's not always as obvious. It depends on the size of the leak. Also, its usually when you've been holding the brake for a few moments before it starts to idle down, but I suspect that if the leak was bad enough it could start doing it right away.

[ROKTOY829]

check your idle mixture screw it could be loose causing it.

[Tallchevy]

Did you use the intake that came off your engine?

[cam011]

http://www.4crawler.com/4x4/TLCA_TruckTech/TruckTech.04.09.html

Second one down on that page.

[MiniSimp]

Here is another possibility from PBB

Idle Drop

"It's an 85 xcab efi. When I hit the brakes my idle drops off 500 rpms or so then recovers, over and over again. It dosen't happen when It's warming up, just when hot."

"I would bet you that your idle is set to high. Sometimes the screw works loose with vibration. If your idle is at like 1100, it's too high. With the engine warm, try lowering the idle at the intake manifold to about 750 or so. That will probably solve your problem. Mine was doing the same thing last week after the new header. Adjusted the idle and it's fine. "

"The EFI computer receives a signal from the brake circuit that tells it that the brakes are being applied. This causes the computer to shut off the injectors if the RPM's are over a certain level and the engine is in "closed loop" as engine power should not be needed if the brakes are being applied.I believe the set point for the injector cut out is 850 to 900 RPM. This is what causes the surging - your idle RPM is too high, when the brakes are applied the injectors are cut out until the RPM's drop below this level. The engine then run's again. This only happens when the engine goes into "closed loop" so this will not happen when the engine is at a higher idle speed warming up. I am willing to bet your idle speed is around 1000 RPM when this happens. To fix this problem, simply adjust your warm idle speed to 750 RPM as per the factory. "

[tech201]

I had this same problem took out the idle screw replaced the o-ring cleaned the throttle body and the problem was fixed.

[93tonkatoy]

X2 on resetting the idle speed.

If you find that you can screw the idle screw all the way in, and still not drop the idle to 750, then, yes, I would suspect a small vacuum leak. It does not take much air to bump the idle up to 1000 rpm.

[snowrun]

Idle is to high or it is your throttle position sensor out of adjustment or just plain out to lunch

[sam2145871 [OP]]

Thanks for the suggestions guys. It was the idle. Good to go now.