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Discussion Starter #1
Just throwing this out there in case anyone has a similar problem. My GTV6 has been running really well for a long time, but it always had a bothersome idle, especially when the engine was cold. I covered up the problem by converting to a manual AAV. A couple of weeks ago the cheap *** lawn mower cable I installed as actuator failed, so I had to go back to the Bosch AAV until I could replace it. In the meanwhile I adjusted the AAV, and yesterday I went to the hardware store and got a couple of different o-rings to replace the one in the idle air valve. (I ended up installing one that's 9/16x5/16x1/8.) That improved things a little bit but the cold idle was still low and uneven. I installed Greg's vacuum kit a couple years ago so I was pretty sure I didn't have an air leak. Then I remembered the factory adjustable vacuum leak on the AFM. I've never messed with that before, but just went ahead and screwed it all the way in (it was out about 4 turns). My idle went smooth and steady immediately. I back it out slowly until I could detect a little unevenness, and then turned it back in 1/4. I also adjusted the AFM 5 clicks richer. I had to take my daughter in to South Station this morning at 35 degrees and the startup idle was perfect and smooth, and it ran beautifully the whole way.
 

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Discussion Starter #4
Actually, that's probably true that the original factory tuning would be no longer correct with the reformulated gas. Don't know how many people still have those screws still at the factory setting though.
 

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Discussion Starter #6
Bill,

Where is the vacuum adjustment?
It's the screw offset on the AFM. It lets in unmetered air as a factory fuel/air trim to fine tune idle emissions. They came from the factory sealed, but most I suspect have been unsealed at this point.
 

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Discussion Starter #7
That's good to know Bill.
I'll keep it in mind when chasing idle issues.
Hi Glenn,

Driving to South Station, it reminded me how much fun it would be to drive through the Big Dig tunnel in the middle of the night and really wind it up. The acoustics would be great!
 

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Huh. My idle has been nuts lately. I'll warm it up, set it at 900, drive for a while, and by the time I get home it's crept back up to 1200 or so, or is wobbling and dipping. I think I might have a leak between the plenum and the manifold, but I also suspect the idle screw is the issue. reading Greg Gordon's page, it seems it's something of a chore to set it correctly. Lots of voltage metering and math and such.
 

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Discussion Starter #9
Huh. My idle has been nuts lately. I'll warm it up, set it at 900, drive for a while, and by the time I get home it's crept back up to 1200 or so, or is wobbling and dipping. I think I might have a leak between the plenum and the manifold, but I also suspect the idle screw is the issue. reading Greg Gordon's page, it seems it's something of a chore to set it correctly. Lots of voltage metering and math and such.
Yeah, That's why I never touched it. But in the end it's just a valve to let in a bit of unmetered air to reduce HC and CO at idle when the O2 sensor is not functioning.
 

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But Mad North-Northwest
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Does the GTV6 L-jetronic go open loop at idle? On the Milano it's closed loop and still using the oxygen sensor to control idle mixture.
 

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Discussion Starter #11
Does the GTV6 L-jetronic go open loop at idle? On the Milano it's closed loop and still using the oxygen sensor to control idle mixture.
My understanding (which may be incorrect) is that the exhaust temp is too low at idle to maintain the sensor at the proper temp for it to function, so it goes to open loop (unless it's been converted to 4-wire). Hopefully someone who knows for certain will chime in.
 

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But Mad North-Northwest
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That's possible. They went to a three wire oxygen sensor with heater in the Milano (and later GTV6, I think), so maybe that's the difference.
 

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This is great info - definitely going to Bookmark this thread!
I've had some weird idle RPM's in my '82, seems the same as yours..
- Art
 

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Well, I pulled off the plenum, cleaned, reseated and tightened all 12 of the hose clamps, checked all of the vacuum hoses and respective clamps, then socked down the idle screw. Voila. Smooth cold idle at 1200 RPM, smooth warm idle at 900 RPM, no wobbling or stalling even in 28 degree weather.

I think you're onto something.
 

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Discussion Starter #16
Well, I pulled off the plenum, cleaned, reseated and tightened all 12 of the hose clamps, checked all of the vacuum hoses and respective clamps, then socked down the idle screw. Voila. Smooth cold idle at 1200 RPM, smooth warm idle at 900 RPM, no wobbling or stalling even in 28 degree weather.

I think you're onto something.
That's great! Glad to hear it helped.

Bill
 
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