Hi brickster,been long time sense on site but has started to drive 240 again. My problem is when idling after a drive it goes real low rpm loping.I have cleaned throttle and IAC.while cleaning the IAC I noticed that the valve is cracked about 16t . Inch open is this normal? Applied power and it open all the way. Is this normal? I think that the IAC only control idle and Think my problem is there. What does everyone else think? Has anyone had this problem. Have other tweets but want get smooth running first. Thanks

Hi,
Glad to see you are back for a bit. The 200’s section is getting lonely. (:-(
The number of threads posted daily are fairly lower than a few years ago.

On the LH 2.4 the IAC has a spring loaded return. It always opens under power and returns onto a preset stop internally when off. The other IAC’s have three pin connectors so the computer modulates in two directions.
I think I saw a plugged hole on the outside that may contain a screw that the factory uses.
I do not remember exactly how much it stays open when off but I think it is a tiny bit.

In any case, if the IAC valve is open by 1/16 of an inch, it is apparently is not giving enough air for it to idle higher than the computer wants. The computer will always adjust pulses of mixture to match the air it gets, if the O2 Sensor is correct. It’s Self tuning, in theory.
It would be my estimation that the gap is normal or not hurting anything. The computer should adjust it within its limits.

The next time you start the car, the engine should “always or every time” rev up higher than a normal idle and then settle back down to the 750 rpm requirement stated on the fender decal.
This means the IAC is working correctly. You never touch the gas pedal!

As far as the AMM going faulty that is a tough call to make! No test for them per say. It’s a case of R&R with a known good one.

The hot idle loping can be caused by a too lean of mixture, in most cases I have found.
It would be better to check for air leaks behind the AMM first. Start with the air accordion hose looking for cracks down in the volutes or abrasion holes on the tops. Best to use a bright light from the inside going outwards.
In case of rich mixture, check your thermostat operation or the coolant temperature sensor for the computer.
Check the plugs color for any story they can tell you about overall running mixture coming off the highway to an idle.

Vacuum hoses are next and make sure they are tight. Usually splits show up on the underside of the nipples they attach to.

Continue to be a good Volvo Brickster and Roll back to us what you find!

Phil

"It would be my estimation that the gap is normal or not hurting anything. The computer should adjust it within its limits."

Yes, the gap at rest is there to provide some idle air should the valve or the circuit controlling it fail. Keeps a poor corroded connection from being the reason your 240 stalled on the RR tracks.

For the OP, I would suggest checking the idle mixture as you suggest by looking at the plugs, or by observing regular switching of the oxygen sensor.



--
Art Benstein near Baltimore

A man and his ever-nagging wife went on vacation in Jerusalem. While they were there, the wife passed away. The undertaker told the husband, "You can have her buried here in the Holy Land for $150 or we can have her shipped back home for $5000. The husband thought about it and told the undertaker he would have her shipped back home. The undertaker asked him, "why would you spend $5000 to have her shipped home when you could have a beautiful burial here, and it would only cost $150????" The husband replied, "Long ago, a man died here, was buried here, and three days later, rose from the dead. I Just can't take that chance".

I also had a poor idle on my 1990 240. Long story short, check the intake manifold fasteners, some of them were very loose! Anyway,that solved my idle problem. We also changed the intake manifold gasket while we were about it.

Hi popdaddy,

Sure happy it's Wednesday (all day long)!


Volvo Maintenance FAQ for 7xx/9xx/90 Cars:
Engine Tune and Performance: Symptoms PDF

https://www.brickboard.com/FAQ/700-900/EnginePerformanceSymptoms.htm
(See items relating to idle yet the listing is not comprehensive.)

A crack in cast IAC (Idle Air Control solenoid) valve housing? 1/16" inch long? Or in the plastic bits where the wire harness connector protrudes? Where is the crack?

I see you posted about finding a use IAC from an 850 in your 2011 post.

idle motor 200 1990
https://www.brickboard.com/RWD/volvo/1506389/220/240/260/280/idle_motor.html

And earlier in 2010:

idle motor question 200 1990

https://www.brickboard.com/RWD/volvo/1398375/220/240/260/280/idle_motor_question.html

FCP Groton Euro: Volvo Idle Control Valve - Bosch 1389618
https://www.fcpeuro.com/products/volvo-idle-control-valve-0280140516



So, a crack here at the plastic connector end?

Other issues can cause a poor idle as you describe.

Air intake leaks at any point from the air filter box to the air port intake manifold gasket. The gasket shrinks and become brittle causing gaps where the intake port should seal to the cylinder head. Wear holes or rips or cracks at the accordion hose between the AMM / MAF and the throttle body. This accordion-style hose can encounter chafing, wearing holes though it, whereever it contacts the inner fender or a wire or vacuum line. Or elsewhere.

Corrosion forming at wire harness connectors and connections to ground and power.

Exhaust leaks usually upstream of the oxygen sensor.

Do you have a CHECK ENGINE light on?

Though not conclusive, have you checked the OBD-1 for fault codes?

https://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm

I'm sure other folks will have better and more conclusive suggestions for you to help you with your fault diagnosis and resolution.

Questions?

Hope that halps yooooooooooooo.

Walmart Coffee with Aldi Baking Cocoa.
--
Give your brickboard.com a big thumbs up! Way up! - Roger Ebert.

Have you tested the Air Mass Meter. I have had trouble with idle from a failing AMM. With key out unplug, start car and idle is different and solid above where it was giving you issues I'd be looking quick for a used one.