Hi and good day to you Spooky Jay,
"idle stabilized at a tad higher than normal (perhaps 800 revs/minute (RPM) versus 700 RPM. I'll adjust this, on a day when temps are higher."
Sorry, Jay, your idle is not adjustable as such. For all LH and Rgeina systems, it's determined by the ECU using purple smoke, magic mirrors, the CPS rpm sensor, the block temp sensor and whether or not the AC compressor is engaged.
The FAQ talks about idle adjustment, but it's actually base idle adjustment. For LH 2.2, there's a base idle adjustment screw (black plastic knob) to adjust the amount of air bypassing the throttle plate -it's adjusted with the IAC forced closed by grounding a wire. There is no equivalent in LH 2.4 and Regina systems which use a different IAC where at rest the spring loaded valve is in the mid-open position rather than in the fully closed position as with LH 2.2.
The other aspect of setting base idle is setting the amount of air getting past the throttle plate in the closed position. Once set at the factory it should not need adjustment, but still worth checking occasionally in case someone has disturbed it (there's usually a drop of blue paint as an indicator). Adjustment is done with the idle plate stop screw on the left side of the throttle body and held in place with a lock nut. Note that the FAQ only describes this under LH systems. Regina adjustment is the same as for LH 2.4. There are two procedures for adjusting base idle with the stop screw. The one described in the FAQ under LH 2.4 involves removing/blocking hoses and setting the base idle at 500 rpm, but it's often difficult to achieve a steady idle at 500 rpm and you need a much more accurate tach than the dash tach. A far simpler method, and as used by many Volvo techs, is to loosen the TPS, hold the throttle plate closed with one hand and advance the idle stop screw until it just touches the stop and you can feel it about to open the throttle plate, then advance 1/4 turn more (1/2 turn for LH 2.2 throttle bodies with the lever and microswitch) and lock in place. In all cases, the throttle body needs to be throughly clean, especially the edge of the throttle plate, the central throat area and the small air holes (remove the brass hose nipples for full access and to ream with a fine wire or 1/8", as I recall, slightly undersized drill bit.
Many people adjust the TPS just past the click point. As long as it's not on the hairy edge, this is usually adequate. Proper TPS adjustment is described in the FAQ under LH systems using a feeler gauge then adjusting for the click. There are actually two specs, and it's not based on LH or Regina, it's based on whether you have a Bosch or VDO TPS switch. The VDO TPS procedure is exactly as in the FAQ, a .25 mm feeler inserted at the stop screw then turn the TPS counterclockwise just to the click and secure, locking luid recommended. The Bosch TPS swicth procedure is simpler, you don't use a feeler gauge, you just hold the plate closed, adjust past the click to end of travel and secure, locking fluid not mentioned. This is all from the Volvo TSB on the topic.
There are other specs mentioned in the TSB, including centering the throttle plate on it's shaft. The plates is centered with the idle stop screw backed right off annd adjusting the brass screw to center the plate for an even amount of light all the way around when looking through to a light source. The throttle shaft should also not extendtoo far such that it may bottom in the TPS switch and bind -a 22mm +/-0.5mm spec is mentioned for how far the shaft should extend out of the throttle body. Some people used to take that opportunity to knife the edge of the throttle plate at an angle (you can find diagrams on performance sites) and file off the tails of the brass screws (peaning the screws to lock them) in order to theoretically reduce air turbulence past the throttle plate, but I think we're talking a 1% improvement at best -I once did it to my 16-valve for amusement, can't say as it made any difference.
It's been asked before whether you can use an LH TPS switch in a Regina car. TPS switches for Regina systems are often not listed on parts sites or are listed as not available. As far as I can tell, yes, you can use either a VDO or Bosch switch with either system, but I can't confirm that myself. The mounting is the same, the connector appears to b the same, the function should be the same (switch on close, switch on WOT, no sense for position otherwise), so I have no idiea what could be different. All that's different is the adjustment spec for VDO vs. Bosch switches as noted above and it's not overly critical. Someone can correct me if I'm wrong here.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now
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