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240 1991 240 with extremely low idle

H

hessam69

Well-known member
Joined
Jun 19, 2009
Location
Sydney, Australia
Hi,

I'm working on a 1991 240 at the moment. I removed and cleaned the throttle body, noticed the idle speed screw had been played with and the TPS was adjusted incorrectly. I cleaned the throttle body properly, loosened the idle speed screw so it no longer had effect, and adjusted the TPS so it would click upon opening of the throttle.

Now the car barely idles, (<500rpm) and stalls. I tested the IAC valve, found it to be working. Swapped it with a known working IAC valve, the problem is still happening. I am getting 12v to the IAC valve connector also.

What are some possible causes?

Thank you
 
Had this happen as well, easy fix:

Idle speed screw needs to be adjusted so the engine runs ~500rpm with the iac hose closed off.
Take some fiddling to reach that setting. And the TPS needs to be adjusted again when you change the idle set screw adjustment.
 
How do you close the IAC valve hose? Is it the hose from the manifold or the one from the intake pipe? Also by turning the idle speed screw in to raise the idle, doesn't that defeat the purpose of having an IAC valve in the beginning? I had thought the IAC valve's job was to keep the idle at 775rpm with a closed throttle
 
hessam69 said:
Hi,

I'm working on a 1991 240 at the moment. I removed and cleaned the throttle body, noticed the idle speed screw had been played with and the TPS was adjusted incorrectly. I cleaned the throttle body properly, loosened the idle speed screw so it no longer had effect, and adjusted the TPS so it would click upon opening of the throttle.

Now the car barely idles, (<500rpm) and stalls. I tested the IAC valve, found it to be working. Swapped it with a known working IAC valve, the problem is still happening. I am getting 12v to the IAC valve connector also.

What are some possible causes?

Thank you
Click to expand...

So you're referring to the throttle adjustment screw, since LH 2.4 doesn't have an 'idle' adjustment screw ?

;-)
 
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