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Old 01-16-2014, 10:56 AM   #1
sshawn
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Default Idle Air Control Valve Removal?

All,

Working with a 87 740 turbo with the 2.2 / 117k.

Do I need to have the IAC valve? I believe it is having issues, and wondering if I can eliminate it? Application is an endurance racer.
- If there is a idle thumbscrew adjustment, why do I need an IAC valve?
- Will it be enough to just bump up the thumbscrew and rid of the IAC?
- Is the IAC just to help with cold starts and air conditioner idle increases?
- If I disconnect the harness, would the ECU remain in WTF mode? (Does the IAC provide any feedback to the rest of the system)?

My aim in simplicity. For our application I would like to rid of anything not that important. Reading 20-21 ohms on the IAC when I see spec to be 10-14. We've never had a clean idle, assuming this is the culprit.

Thanks,
Shawn
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Old 01-16-2014, 11:42 AM   #2
7mgtesup
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It's not needed on a race application, I drove on the road for a year without one. It just ment low idle when cold and high idle when warm, also poor driveability at very low rpm (below 1300rpm the car would shunt). It will give you a MIL not having it though.
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Old 01-16-2014, 03:21 PM   #3
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Quote:
Originally Posted by 7mgtesup View Post
It's not needed on a race application, I drove on the road for a year without one. It just ment low idle when cold and high idle when warm, also poor driveability at very low rpm (below 1300rpm the car would shunt). It will give you a MIL not having it though.
Drove without it? Such as disconnected electronically?

MIL: Do you have the Jettronic 2.2? I didnt think there was a light for the 2.2, on the 2.4 however, I am almost certain there is.

Did it degrade performance at all?

Thanks,
Shawn
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Old 02-10-2014, 11:49 AM   #4
7mgtesup
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Quote:
Originally Posted by sshawn View Post
Drove without it? Such as disconnected electronically?
It was on the shelf in my garage along with the wiring.

Quote:
MIL: Do you have the Jettronic 2.2? I didnt think there was a light for the 2.2, on the 2.4 however, I am almost certain there is.
Sorry missed the bit about 2.2, I'm on 2.4

Quote:
Did it degrade performance at all?
Apart from the low speed shunting no, I ran a 13.75@101 without it.

Although I was running in blow through mode (AMM after the intercooler) it won't work with the AMM in the stock location as you will stall when coming down to idle.

Sorry for the late reply.
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Old 02-13-2014, 09:12 PM   #5
sshawn
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Quote:
Originally Posted by 7mgtesup View Post

Although I was running in blow through mode (AMM after the intercooler) it won't work with the AMM in the stock location as you will stall when coming down to idle.

Hmmm, blow through setup... I never thought about that before. What are the advantages in doing that? We removed the IAC for the race, all was well. Ended up adjusting the butterfly high to keep idle about 1100 or so. No problems at all doing that.

Thanks,
Shawn
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Old 02-14-2014, 05:45 AM   #6
7mgtesup
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No real advantages apart from the AMM see's the real inlet air temp rather than ambient. And you can run a dump to atmosphere BOV without the rich spike after a gear change.
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Old 02-14-2014, 06:48 AM   #7
sshawn
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Just trying to think hard about this... If it sees the hotter IC temps, it should be a tad bit leaner right? Whereas on the filter side it should be cooler. I'm going off the principal of head temps being cooler for rich'er.
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Old 02-17-2014, 08:11 AM   #8
7mgtesup
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Hotter air has less mass so less fuel needs to be added to reach the desired AF ratio. So you should get more accurate fuel metering (unless volvo put in some compensation for this).
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Old 02-17-2014, 10:01 AM   #9
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I've removed my IAC completely. had to turn the throttle plate screw in to get if off the tps so it would idle. I have my AMM in the stock location, I have never stalled at idle or coming down to idle. I do get a rich spike on the afr gauge, when I get my foot out of it after a wot pull. RUnning 2.4... 92'740t.
Quote:
Originally Posted by 7mgtesup View Post
It was on the shelf in my garage along with the wiring.



Sorry missed the bit about 2.2, I'm on 2.4



Apart from the low speed shunting no, I ran a 13.75@101 without it.

Although I was running in blow through mode (AMM after the intercooler) it won't work with the AMM in the stock location as you will stall when coming down to idle.

Sorry for the late reply.
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