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940 IAC - is it supposed to be wide open, or shut, with no power?

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SmittySmithsonite
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Year and Model: 1993 940
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940 IAC - is it supposed to be wide open, or shut, with no power?

Post by SmittySmithsonite »

New member here. My expertise is on domestic vehicles. Trying to diagnose a bad IAC on this 940 with no service info - frustrating as hell!

Vehicle - '95 Volvo 940 wagon 2.3L 4-cylinder, Bosch system.

All my testing has narrowed it down to the IAC. What I want to know is, as the unit is sitting in my hand, should I be seeing right inside the unit through the port that's pointing down in the first pic? From what I've been reading, this should be closed off with no power applied. Also, this unit has 2 pins - not 3 - for the electrical connection. When I energize the unit, the shutter flips around briefly, and can barely be seen through the port. I can blow air through it regardless of having 12v at the pins, or 0v at the pins.

Thing looks fairly new, and is extremely clean inside as you can see. I sprayed some silicone spray in there to lube and clean things up a bit (not that it needed it - just in case it may have been sticking). Anyone ever looked inside one of these, or better yet, anyone have a known good one laying around to look at? I suspect I should be seeing the shutter closing off that port when there's no voltage applied to the pins. I just need 100% confirmation of this.

Any and all info will be greatly appreciated!
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jimmy57
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Re: 940 IAC - is it supposed to be wide open, or shut, with no power?

Post by jimmy57 »

It should have a rest position for that valve that should give 900-1200 RPM idle.
SmittySmithsonite
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Re: 940 IAC - is it supposed to be wide open, or shut, with no power?

Post by SmittySmithsonite »

Thanks Jimmy - you're the only one who answered my question out of 3 forums. 8)

I finally have the answer here in my hand. Hopefully this will help someone else down the line who's attempting to keep these 940's on the road.

I hate winging parts at something without thorough troubleshooting, and being 200% sure that a new part will fix the problem. Without service info, I took a chance, based on my limited testing and observation of the old part, and purchased a brand new Bosch idle air control valve. Lo and behold, the shutter is 90% CLOSED on the new one! There's just a tiny opening to the left - 90% of the opening is blocked by the shutter. Exactly what I suspected. Made the right call, and for that I'm happy.

Here's pictures of the new unit taken in the exact location of the old unit in the post above (down the tube with the arrow on it).

New Bosch idle air control unit
New Bosch idle air control unit
Shutter 90% closed!
Shutter 90% closed!
Slight opening (to left inside tube) to allow default idle air
Slight opening (to left inside tube) to allow default idle air
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93Regina
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Re: 940 IAC - is it supposed to be wide open, or shut, with no power?

Post by 93Regina »

SmittySmithsonite wrote: Fri Aug 23, 2019 2:00 pmI finally have the answer here in my hand.
Are you sure?

With a choke cable, hooked a water valve, one could rig up a manual IAC....homework is required, but it should work
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E Showell
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Re: 940 IAC - is it supposed to be wide open, or shut, with no power?

Post by E Showell »

What was the effect on drivability with the bad IAC?
'98 V70 NA FWD 5 spd, silver sand metallic (sold)
'99 V70 NA FWD Auto, dark blue (sold)
'99 S70 NA FWD Auto, black (sold and resurrected -- Don't cry for me Argentina . . . )
'07 S80 3.2 FWD Auto, Barents Blue Metallic
'06 V70 R AWD Auto, Sonic Blue Metallic
'04 XC70 Ruby Red Metallic
'95 855 auto (sold)
'86 245 manual (sold)
'05 V70 T5 M (totalled)
'06 V70 FWD Auto (totalled)
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93Regina
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Re: 940 IAC - is it supposed to be wide open, or shut, with no power?

Post by 93Regina »

E Showell wrote: Sat Nov 30, 2019 4:40 pmeffect on drivability with the bad IAC?
IAC - Idle Air Control

IAC is related to idling RPM....irrelevant for roadway drivability...throttle plate is in control.

A bad IAC would have to be defined....stuck is what position...allows extra air, higher RPM...allows smaller amounts, lower RPM (stall out possible).

IIRC, IAC gets a "frequency" based signal (aka duty cycle) when throttle switch is in idle position. Once off idle switch position, your foot is in control
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E Showell
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Re: 940 IAC - is it supposed to be wide open, or shut, with no power?

Post by E Showell »

Reason I ask, daughter's H.S. buddy has a '92 940. I am told it can't be driven over about 40 mph. Not exactly sure what the issue is. I'll try to get more data and report back.
'98 V70 NA FWD 5 spd, silver sand metallic (sold)
'99 V70 NA FWD Auto, dark blue (sold)
'99 S70 NA FWD Auto, black (sold and resurrected -- Don't cry for me Argentina . . . )
'07 S80 3.2 FWD Auto, Barents Blue Metallic
'06 V70 R AWD Auto, Sonic Blue Metallic
'04 XC70 Ruby Red Metallic
'95 855 auto (sold)
'86 245 manual (sold)
'05 V70 T5 M (totalled)
'06 V70 FWD Auto (totalled)
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93Regina
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Re: 940 IAC - is it supposed to be wide open, or shut, with no power?

Post by 93Regina »

E Showell wrote: Sat Nov 30, 2019 7:35 pmcan't be driven over about 40 mph.
LH 2.4 has a limp home mode....Rex-I/Regina I've never heard of a limp home mode.

Bypassing FPR, or low rail pressure (fuel pump or filter defective) would be suspect....by 1993, there was a quick test for checking rail pressure at rail.
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E Showell
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Re: 940 IAC - is it supposed to be wide open, or shut, with no power?

Post by E Showell »

Overdrive relay bad?
'98 V70 NA FWD 5 spd, silver sand metallic (sold)
'99 V70 NA FWD Auto, dark blue (sold)
'99 S70 NA FWD Auto, black (sold and resurrected -- Don't cry for me Argentina . . . )
'07 S80 3.2 FWD Auto, Barents Blue Metallic
'06 V70 R AWD Auto, Sonic Blue Metallic
'04 XC70 Ruby Red Metallic
'95 855 auto (sold)
'86 245 manual (sold)
'05 V70 T5 M (totalled)
'06 V70 FWD Auto (totalled)
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93Regina
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Re: 940 IAC - is it supposed to be wide open, or shut, with no power?

Post by 93Regina »

E Showell wrote: Sun Dec 01, 2019 8:17 amOverdrive relay bad?
940s could have had AW70s, or AW71Ls transmissions.

Kickdown cable may not be working correctly....so upper range gears are absent. If so, engine most likely is using higher RPMs

OD relay circuit would only affect shifting into OD...higher speeds than 40mph exist....when OD is kicked out, this is for heavy loads or mountain like driving. Hence, 65 mph....

Kickdown cables fail...they all get replaced....hence, if a gear shifting issue, kickdown cable needs replacement, or valve-body has an issue.
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