240 1991 240 idle keeps going down

Hi,

I recently serviced a 1991 240 LH2.4 throttle body (throttle screw was futzed with) and cleaned it and the IAC valve and reset TPS. Now, when cold the idle is strong but as the coolant temp rises, the idle keeps lowering itself, to the point where the engine stalls. It is not hunting up and down at idle, it is smooth but slowly goes slower and slower. I have thoroughly checked for vacuum leaks (spray over entire manifold) and none were to be found. Drives well otherwise.

What could be my problem?

Thank you

Sounds like the idle control is disabled and the throttle plate is fully closed after the adjustment. Did you switch connectors possibly?

dl242gt said:

Sounds like the idle control is disabled and the throttle plate is fully closed after the adjustment. Did you switch connectors possibly?

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+1 on throttle plate closed, to me it sounds like that is the issue.
Adjust the idle stop so engine runs 500rpm with hose to iac closed.
That's what solved the idle dip and stalling issue on my 240.

Thanks for your replies.

I'm curious, shouldn't the throttle plate be fully closed when adjusted properly? I thought it was the ECU's job to modulate the amount of air needed by opening the IAC valve to keep the idle around 750rpm.

My problem is that on first cold start up the idle is perfect at 750rpm. Then it slowly goes down as the coolant temp rises. After about 3 minutes it will stall. Something's not right

You need to open the throttle plate by turning the screw ? turn past contact. You may need to loosen and readjust the throttle switch.

Ok. Now I'm convinced. Thanks to all who replied