I've been chasing a low/hunting idle on my 93 940 turbo. I've cleaned the throttle body and IAC, with no effect. I'm going to check for vacuum/boost leaks on the inlet air side, probably using pressurized air as per the tool in the FAQ. I'm also going to verify the TPS and ECT.

I'm also going to check the idle adjustments, but I'm confused a bit by the instructions outlined in the Haynes 940 manual vs. the FAQ.

Haynes steps are as follows:

Idle linkage:
- ensure that when cable drum pushed off endstop with 2.5 mm feeler blade, that gap between throttle lever and adjustment screw is from 0.1 and 0.45 mm. (This is the adjustment screw that mounts on the throttle lever, not the adjustment of the larger nut that attaches the lever to the throttle plate shaft)
- to achieve the above spec, adjust the throttle link rod (ball socketed connection between drum and throttle lever)

Idle speed adjust:
- pinch off IAC; check that idle drops under 500 or stalls
- if it doesn't, leave IAC pinched, loosen the throttle spindle nut (the one attaching the throttle lever to the throttle plate shaft) and turn the shaft with the set screw until an idle of from 480 to 520 is achieved
- tighten the locknut
- remove the IAC hose clamp


I have two questions:

1) Is there an idle linkage adjustment in the FAQ? I couldn't find one. Maybe this should be added, so no one proceeds to do a throttle plate adjustment, and compensates for a misadjusted link with a throttle plate misadjustment.

2) In the FAQ idle speed adjust for 2.4, it specifically states that the pinch on the IAC hose is supposed to be removed before making the adjustment. This is opposite to Haynes, which says to remove it afterwards. It seems to me that Haynes is correct, in that when the hose clamp is removed after the 480-520 rpm adjust, the additional air provided by the IAC will bring the idle up to the specified 750 rpm. In the FAQ procedure, since the throttle spindle nut is being adjusted with the IAC hose open, the adjustment to 480-520 would be the final idle rpm value, since nothing gets changed afterwards.


One other minor correction I think the FAQ could use: the "Adjusting the LH2.4" idle adjust section links to the 2.1/2.2 "Setting Base Idle" section, but this linked section does not apply to 2.4 (as stated at the end of the "Setting Base Idle" section).

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David Armstrong - '86 240(350k km?), '93 940T(270k km), '89 240(parts source for others) near Toronto