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Cleaning DIY: 850 IAC (Idle Air control valve) cleaning

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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jreed
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Volvo Repair Database Cleaning DIY: 850 IAC (Idle Air control valve) cleaning

Post by jreed » Mon Mar 19, 2012 3:08 pm

It got warm here a couple of days ago for the first time this year (~80-85F) and our '97 855 GLT Volvo at 155k miles suddenly started to have a wandering idle speed and stalling at idle, but only when the car was fully warmed up. The stalling symptom was worst right after restarting the car after it had been running for a while (hot start). I first tried disconnecting the MAF but this did not change the wandering idle and stalling. So, I read up on stalling and rough idle on MVS, found a good post by Ozark Lee (http://www.matthewsvolvosite.com/forums ... =1&t=17425) and so decided to remove the IAC and give it a good cleaning. Since there wasn't already a good illustrated write-up, I took some photos along the way:

Step 1: Remove the throttle cover. This requires a T25 screwdriver to loosen the screw on top. When you remove it, the IAC is visible underneath.
IMG_5945.jpg
IAC valve under the throttle cover
Step 2: Disconnect clamp. I used a sharp flat blade screwdriver to pry off the Oetiker clamp holding the IAC hose to the vacuum nipple (I removed the other two Oetiker clamps on the IAC later, after pulling it out of the car). Then I pulled the IAC hose off of the vacuum tree.
IMG_5947.jpg
Screwdriver prying the Oetiker clamp loose from the IAC-Vacuum tree hose.
Step 3: Disconnect the electrical connector on the back of the IAC. Loosen hose clamps at throttle and intercooler and pull hoses and IAC from throttle. There is a black rubber collar around the IAC valve that has two ears underneath that can be squeezed together to release the IAC valve from support bracket.
IMG_5948.jpg
IAC and hoses after disconnecting electrical connector and hose from throttle.
Step 4: Remove the Oetiker clamps at the IAC connectors. Inspect and clean internal plate. My IAC valve was original (dated '96) and had never been cleaned as far as I know. There was a lot of yellow and black varnish on the plate that needed to be cleaned off. I used MAF cleaner (hexane) which was not very effective at dissolving the varnish. I used cotton swabs and a flat screwdriver blade to wipe and scrape the varnish off and used the MAF cleaner to flush away loosened deposits. I think the varnish had built up to the point that it caused the IAC valve to stick or respond slowly, making the idle wander and the car likely to stall. If you twist the IAC in your hand the plate should rotate freely.
IMG_5950.jpg
IAC valve with ~15 years build up of varnish (pre-cleaning)
Step 5. After cleaning, twist the IAC to make sure the internal plate rotates smoothly without sticking or binding. During reinstallation I used new hose clamps to replace the three Oetiker clamps I removed. While I had the intake hose removed from the throttle, I took the opportunity to clean the throttle plate. After putting the IAC and hoses back together, the car is running well again.
IMG_5957.jpg
IAC valve after cleaning.
This worked great for me and was a lot cheaper than buying a new IAC (~$200). If I had to do it again, I would probably have bought some more powerful solvent like throttle body cleaner to make cleaning out the varnish a little faster and easier.
1997 855 GLT (Light Pressure Turbo) still going strong. Previous: 1986 240 GL rusted out in '06, 1985 Saab 900T rusted out in '95, 1975 Saab 99 rusted out in '95, 1973 Saab 99 rusted out in '94

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matthew1
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Re: Cleaning DIY: 850 IAC (Idle Air control valve) cleaning

Post by matthew1 » Mon Mar 19, 2012 9:14 pm

Beauty tutorial, great photos. Thanks Jreed. This is going in the VRD.
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1997 850 T5, MSD ignition coil, Hallman manual boost controller, injectors, R bumper, OMP strut brace [gone]
2004 V70 R [gone]

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TravBickle
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Re: Cleaning DIY: 850 IAC (Idle Air control valve) cleaning

Post by TravBickle » Tue Mar 27, 2012 10:08 pm

I need a little help with this. Are the two tubes/hoses going into the IAC supposed to be hard as rock and/or brittle? Mine are and I had to stop the job for fear of cracking them. I think they need to be replaced so my question is are they a specialty item or do I just need to get the right size and what kind/where from? For the sake of the forum, let's say I am decent with a wrench but illiterate when it comes to car vocabulary so I am looking for specifics. In other words, I would like to buy/order these hoses immediately so again; what do I need? and can you recommend clamps also? I owe more to this forum then just my one thank you so far (fuel pump replacement), so at some point I will try to contribute the plethora of experiences from the last 3 months.
Next steps: Clean IAC, Clean Throttle Body, Clean Flame Trap, Replace Cap & Rotor (Just did plugs and wires), Fix Rear Washer Sprayer . . . And I think it posts automatically but this is for a 1995 Volvo 850 Non-Turbo. Thanks all.

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erikv11
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Re: Cleaning DIY: 850 IAC (Idle Air control valve) cleaning

Post by erikv11 » Tue Mar 27, 2012 10:50 pm

Hoses: They are not supposed to be hard as a rock or brittle. They are rubber. Sounds like they need replacing. Specialty item.

You want idle control valve inlet hose and idle control valve outlet hose. Here are some prices and part numbers for your vehicle: http://www.fcpeuro.com/Volvo-parts/850/ ... &year=1995. Going to run you about $35 + $10, no idea why they are so different in price.

You won't likely find these at a generic auto parts store, and if you do they may be low quality junk that needs replacing again in a year. So I would order them but you never know, good luck if you try to shop around locally. Heck the FCP prices aren't much from list, i would try calling the dealer and see what they want for them. That one hose is $35 I don't even trust they have the right one - at least at a dealer you can match it up with the one on the car (drive down there).

Regular, screw-type hose clamps will do fine for this application.
'95 854 T5-R, Motronic 4.4, 185k
'96 855 NA, 145k
'98 S70 NA, 220k (living out west)
'98 V70, T5 tune-injectors-turbo, LPT engine, 286k
'06 S60 R, 167k
'99 Camry V6 :shock: 125k
gone: '96 NA 850 210k, '98 NA V70 182k

TravBickle
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Re: Cleaning DIY: 850 IAC (Idle Air control valve) cleaning

Post by TravBickle » Wed Mar 28, 2012 12:10 am

Thanks Erikv11. Exactly the info I needed and thanks for the advice. I want to do it right so might try the local dealer if I can get to it tomorrow. I'm a new Volvo owner, but obviously not of a new Volvo, and it's already starting to feel like an obsession... is that normal? Ok, I'll try to update when I have some news.

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jreed
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jreed

Re: Cleaning DIY: 850 IAC (Idle Air control valve) cleaning

Post by jreed » Wed Mar 28, 2012 4:49 am

The hose clamps I used to replace the Oetiker clamps were AWAB brand, with diameter ranges of 18-28mm (qty 2) and 24-34mm (qty 1). I got them from the dealer.

eEuroparts has similar ones here that will probably work as well:
http://www.eeuroparts.com/Main/PartDeta ... ?id=988024
http://www.eeuroparts.com/Main/PartDeta ... ?id=981707
1997 855 GLT (Light Pressure Turbo) still going strong. Previous: 1986 240 GL rusted out in '06, 1985 Saab 900T rusted out in '95, 1975 Saab 99 rusted out in '95, 1973 Saab 99 rusted out in '94

TravBickle
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Re: Cleaning DIY: 850 IAC (Idle Air control valve) cleaning

Post by TravBickle » Thu Mar 29, 2012 11:23 am

Thanks. I did order the hoses through the dealer for the reasons ErikV mentioned; close in price and I can drive over there when they get them in a day or two. So I will likely ask for the clamps you mention then. I'd prefer them to the Oetiker for sure. Oh, email just came saying hoses are in already. Sweet

CTHarris88
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Re: Cleaning DIY: 850 IAC (Idle Air control valve) cleaning

Post by CTHarris88 » Thu Apr 05, 2012 5:35 am

I've had my 850 for 3 weeks now. Drives fine. But i am having this problem. CEL is on and reading P0171. Bank 1 system too rich.
My family mechanic is saying it's an o2 sensor. He also told me he needed to call a guy he deals with when he gets european cars to talk to him about it. 2 weeks later I havent heard from the mechanic. I called today and he told me he hasnt talked to the guy. Not sure what this place is doing. What i am sure of is my car is sometimes stalling when idling (at stop signs and lights etc.) It sounds as if its skipping when in idle. I'm scared, this is my first car and im in love already. It's such a nice ride, i just dont want matters to get worse. Should i try cleaning the IAC? What will i need to go about doing so?

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erikv11
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erikv11

Re: Cleaning DIY: 850 IAC (Idle Air control valve) cleaning

Post by erikv11 » Thu Apr 05, 2012 7:19 am

a p0171 is almost always a bad MAF or a vacuum leak between the MAF and the intake. Unlikely, but possible, that the problem is an O2 sensor. I wouldn't use that mechanic for your Volvo.

Test MAF: try unplugging the MAF. If the car runs better, then you need a new MAF. Aftermarket replacement will not work, you need a unit that is Volvo- or Bosch-branded (same thing).

Vacuum leaks: get a can of starting fluid and spray it on the various vacuum while the car is idling. If the idle surges, you have found your leaky hose.

My money is on the MAF.

EDIT: it doesn't hurt to try cleaning the IAC - that is basically free and your 96 probably needs it anyway.
'95 854 T5-R, Motronic 4.4, 185k
'96 855 NA, 145k
'98 S70 NA, 220k (living out west)
'98 V70, T5 tune-injectors-turbo, LPT engine, 286k
'06 S60 R, 167k
'99 Camry V6 :shock: 125k
gone: '96 NA 850 210k, '98 NA V70 182k

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erikv11
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Year and Model: 850, S/V70, 06 S60R
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Re: Cleaning DIY: 850 IAC (Idle Air control valve) cleaning

Post by erikv11 » Thu Apr 05, 2012 7:24 am

One other thing: the first place to check for a vacuum leak, is the rubber elbow on the passenger side end of the intake manifold. You will need a flashlight to see it, it is sort of tucked behind the power steering pump. Very common failure item. If it is rotted out and falling apart, then the car probably needs a PCV job too.
'95 854 T5-R, Motronic 4.4, 185k
'96 855 NA, 145k
'98 S70 NA, 220k (living out west)
'98 V70, T5 tune-injectors-turbo, LPT engine, 286k
'06 S60 R, 167k
'99 Camry V6 :shock: 125k
gone: '96 NA 850 210k, '98 NA V70 182k

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