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CosmicBike · Apr 10th, 2020, 15:48

A little digging led me to the 'Brickboard' forum, and an article on setting the base idle for LH2.4 equipped models, outlined below.

Setting Base Idle Specs and TPS on Bosch LH2.4-Equipped Cars . [Adapted from Volvo Service Manual 32043/1]
Cleaning the Throttle Body: See the discussion in Engine:Performance for more information
Adjusting the LH2.4:
1. Adjusting Idle Linkage Rod.
Ensure that when the cable drum is pushed off its endstop with a 2.5 mm feeler blade, the 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 rod between drum and throttle lever)
2. Checking the Throttle Body (Plate and Throttle Position Switch) Adjustment
Connect an accurate tachometer then warm up the engine. Let it idle in Park with a/c off. Pinch off the hose between the air intake and the IAC valve (don't damage the hose with something sharp!) Idle speed should drop below 500 rpm, or the engine may stop: both are normal. If idle speed does not drop, adjust as below.
3. Adjusting the Idle Speed
On the front side of your throttle body, there is an adjustment screw. Loosen the lock nut. Start the engine and turn the adjustment screw until idle is 480-520 rpm. Switch off the engine and tighten the lock nut while holding the adjustment screw so it doesn't turn.
4. Checking the TPS Adjustment.
Check the gap between the adjustment screw and the throttle lever with a feeler gauge. Insert a .45mm feeler gauge. There should be no click from the Throttle Position Switch on the rear side of the throttle body when the throttle is closed. Then insert a .15mm feeler gauge. There should be a click from the TPS when the throttle is closed. If these are incorrect, then adjust as below.
5. Adjusting the TPS.
Loosen the TPS adjustment screws holding it to the throttle body. First turn the TPS clockwise (away from the electrical connector) until it stops. While keeping your finger on the throttle disk so it won't move, turn the TPS counter-clockwise (toward the connector) until you hear or feel a click. Continue turning until it stops, then tighten the screws. Go back to step 3 above to check the adjustment.

This matches what I have fitted to my 240, so I followed it this morning. I cannot get the idle below 1100rpm. I have to be honest, it's a minor irritant. The only thing left is the possibility that the new IAC valve I fitted, being a generic item as opposed to a genuine Bosch unit, is the reason. The Haynes manual is quite adamant that you must use the correct model number of IAC as they have a base setting fixed dependant on model No.

I can live with the minor niggle, she's now running really well with just the gearbox oil to change. After that it's cosmetics and the boot hinge wiring.

Apr 10th, 2020, 15:48	#87
CosmicBike Senior Member Last Online: Yesterday 13:59 Join Date: Dec 2019 Location: Surrey	A little digging led me to the 'Brickboard' forum, and an article on setting the base idle for LH2.4 equipped models, outlined below. Setting Base Idle Specs and TPS on Bosch LH2.4-Equipped Cars . [Adapted from Volvo Service Manual 32043/1] Cleaning the Throttle Body: See the discussion in Engine:Performance for more information Adjusting the LH2.4: 1. Adjusting Idle Linkage Rod. Ensure that when the cable drum is pushed off its endstop with a 2.5 mm feeler blade, the 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 rod between drum and throttle lever) 2. Checking the Throttle Body (Plate and Throttle Position Switch) Adjustment Connect an accurate tachometer then warm up the engine. Let it idle in Park with a/c off. Pinch off the hose between the air intake and the IAC valve (don't damage the hose with something sharp!) Idle speed should drop below 500 rpm, or the engine may stop: both are normal. If idle speed does not drop, adjust as below. 3. Adjusting the Idle Speed On the front side of your throttle body, there is an adjustment screw. Loosen the lock nut. Start the engine and turn the adjustment screw until idle is 480-520 rpm. Switch off the engine and tighten the lock nut while holding the adjustment screw so it doesn't turn. 4. Checking the TPS Adjustment. Check the gap between the adjustment screw and the throttle lever with a feeler gauge. Insert a .45mm feeler gauge. There should be no click from the Throttle Position Switch on the rear side of the throttle body when the throttle is closed. Then insert a .15mm feeler gauge. There should be a click from the TPS when the throttle is closed. If these are incorrect, then adjust as below. 5. Adjusting the TPS. Loosen the TPS adjustment screws holding it to the throttle body. First turn the TPS clockwise (away from the electrical connector) until it stops. While keeping your finger on the throttle disk so it won't move, turn the TPS counter-clockwise (toward the connector) until you hear or feel a click. Continue turning until it stops, then tighten the screws. Go back to step 3 above to check the adjustment. This matches what I have fitted to my 240, so I followed it this morning. I cannot get the idle below 1100rpm. I have to be honest, it's a minor irritant. The only thing left is the possibility that the new IAC valve I fitted, being a generic item as opposed to a genuine Bosch unit, is the reason. The Haynes manual is quite adamant that you must use the correct model number of IAC as they have a base setting fixed dependant on model No. I can live with the minor niggle, she's now running really well with just the gearbox oil to change. After that it's cosmetics and the boot hinge wiring.