1982 240, B21,175K. The idle is surging up and down, sometimes it's OK but then it stays at 1,500 RPM. The Air Idle Control Valve looks newly replaced. When uplugged it does nothing noticeable. This valve seems impossible to find. Also, there is an unplugged sensor on the driver's side sort of at the fuel line. Plugged or not, makes no difference. Ideas?

Your '82 240 will be K-Jetronic injection.

Are you talking idle surging that either slowly or rapidly fluctuates up and down during running? Or an incorrect idle that after warmup either stays too high or sometimes goes too low?

Yes, check everywhere for split/loose rubber hoses, especially the air intake hoses at the idle adjusting screw. If the idle adjusting knob is too far open or the rubber o-ring is disintegrated then you could have an air supply problem that causes an incorrect or inconsistent idle, but not surging.

That unplugged unit on the fuel line is the CPR control pressure regulator, aka. frequency valve. I'd guess that's your prime suspect. It affects mix and consequently idle. It needs to be connected and they do occasionally fail. The main symptom of a failed CPR is poor acceleration and bad gas mileage, secondary to that would be a bad idle. Proper diagnosis is done with a fuel pressure gauge. You will need one that has Bosch K-Jet fittings, not just Bosch fittings -lots online about that.

Another possibility is a problem in the air control unit. The air flow sensor plate may be sticky/worn or misaligned and not always fully closing. If there were problems inside the fuel distributor, like sticky/worn metering needles, I'd expect mostly poor running, not so much idle issues.

One of our K-jet experts here, like Art, will almost certainly know what's likely wrong, especially if you can elaborate on the surging.

BTW The auxiliary air valve is the cold idle air valve. If it ever fails (there's a little heater element on the bi-metallic blade inside) then it may cause a high warm idle or at least a very poor warmup correction, but not surging. If it ever wears out (it may become a bit sticky, like a wear notch in the bi-metallic blade) then cold or warm idle may not be properly achieved. The main idle adjusting screw is first used to set the base idle to spec when fully warm. The adjusting nut on the auxiliary air valve can later be used to set cold idle to spec (based on ambient temp) when the block is stone cold. The adjusting nut should rarely, if ever, need touching. To check that it's working, sight through the air tube with a light and mirror. For a stone cold engine it should be over half open. For a fully warmed engine, right after shutdown it should be almost fully closed (a tiny crescent moon of light is what you normally want to see). Although not your problem, while I'm on the topic, note if the paint on the adjusting nut has been disturbed, meaning someone who may not have known what they were doing has touched it. A proper mechanic should add a drop of touchup paint or nail polish when they're done. Also note that there's normally an alignment arrow on the electrical connector that should stay lined up with the mark (fin) on the valve body. (Occasionally, people like me have turned the electrical connector a few degrees if a wear groove has formed in the bi-metallic blade that's causing cold idle problems.)

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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Your '82 240 will be K-Jetronic injection.

Dave, there's a chance the fuel system may be LH 1.0. The mention of, "Air Idle Control Valve," makes me wonder if that's what we're dealing with. I must say, though, I seem to recall that some B21F engines had the constant idle system starting in '81. Thus they would have the IAC valve which, BTW, eliminates the AAV in those engines.


That unplugged unit on the fuel line is the CPR control pressure regulator, aka. frequency valve.

Just for the record, the control pressure regulator and the frequency valve are two different parts. If this is an LH system neither will be present.


I would like to know for sure which system tedv has.


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'79 242, '84 DL 2 door, '80 DL 2 door, '89 DL Wagon, '15 XC70 T6 AWD

Thanks, Don, I'm forever getting slightly confused on the frequency valve being the CPR. Odds of an '82 240 being LH 1.0 are slim, but as you say, the OP said idle air valve. As a I vaguely recall, LH 1.0 was more common in the environmentally sensitive California market. The OP is apparently Oregon, so a distinct possibility. Looking forward to hearing back from the OP here.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

https://ozvolvo.org/archive/

What fuel system do you have and what country are you in?

Hi,

Find the Volvo wiring diagram and other service info for your model year.
Then you can find out what sensor is unplugged. Someone recently posted a link
to one site with service info.
I'd survey all of your vacuum lines for openers, if they are old and beat up
replace it all. Failed rubber vacuum lines will raise heck with your engine.

Good luck, Bill