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was AAR, idle vs voltage maybe?
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airkooledchris
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PostPosted: Sat Dec 10, 2011 2:09 pm    Post subject: was AAR, idle vs voltage maybe? Reply with quote

before I bring him in for questioning, if you had a low (850ish) idle dead cold and high (er) idle when warm (1100) would you first suspect AAR as the culprit?

Later this evening when I have a few hours to spend checking into this I think that's where ill put my efforts. But im open to suggestions if im forgetting anything that would be *more* likely the source.

The theory being that the AAR isn't closing up once warm, and allowing too much unmetered air in - which bumps up the rpm's.

I can obviously adjust the idle to get it happier at warm, but then it's way too low cold. or adjust it perfect at cold which makes it run too fast when warm.
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Last edited by airkooledchris on Sat Dec 10, 2011 7:09 pm; edited 1 time in total
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PostPosted: Sat Dec 10, 2011 2:31 pm    Post subject: Reply with quote

I have found that behavior to be somewhat normal on FI engines. There always seems to be a push/ pull relationship between warm and cold idles. I doubt it's the AAR. Adjusting the mixture and retarding the timing a couple of degrees might help. Also check for vacuum leaks. This is what they call dialing it in. It took me quite a while to get mine right.
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airkooledchris
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PostPosted: Sat Dec 10, 2011 2:52 pm    Post subject: Reply with quote

Mine was dialed but as its gotten colder the swing has been greater.

Ill at least cross it off the list since thats a quicker check than the mixture right now
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PostPosted: Sat Dec 10, 2011 3:03 pm    Post subject: Reply with quote

Do the AAR freezer and oven test, and check for 30 ohms resistance. AAR's do have issues, now that they are getting to the 35 year mark.
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PostPosted: Sat Dec 10, 2011 3:57 pm    Post subject: Reply with quote

airkooledchris wrote:
Mine was dialed but as its gotten colder the swing has been greater.

Ill at least cross it off the list since thats a quicker check than the mixture right now


You know if I found you, that I would rip into you for trying to "fix" a transitory problem using the permanent adjustment.

Warm engine ..... set idle speed to 950-1,000 RPM.

Adjust AAR opening to as open as you can get.

Cold start should light up and stabilize to 1,100-1,300 rpm for a minute and magically drop down in three to four minutes.

Note: (!) an overly rich warm mixture can bog your cold start rpms when the TS II dials in cold fuel mixture calibration !! You can easily check for this - with cold engine idle less than two minutes, pull the decel valve signal hose (the little one) and see if the engine rpms jump noticeably.
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airkooledchris
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PostPosted: Sat Dec 10, 2011 7:08 pm    Post subject: Reply with quote


Link

did a bit more testing and realize seems to have more to do with voltage than anything else.

As the above video shows it will be idling right at 1000 with the headlights and heater fan on, then jump up when you turn them off by 200 rpm

Maybe thats normal, or its due to the dying voltage regulator?
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PostPosted: Sat Dec 10, 2011 8:19 pm    Post subject: Reply with quote

Well, if you think that voltage is the issue, you could probably test your battery and make sure your alternator / fan belt is tight to start with. You can also test the charging rate as well. Should be able to narrow it done.
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airkooledchris
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PostPosted: Sat Dec 10, 2011 9:16 pm    Post subject: Reply with quote

Well, do you see jumps up and down in idle speed upwards of 250 rpm when switching headlights and aux fan on/off? Maybe im just nit picking over nothing
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PostPosted: Sat Dec 10, 2011 10:18 pm    Post subject: Reply with quote

airkooledchris wrote:
Well, do you see jumps up and down in idle speed upwards of 250 rpm when switching headlights and aux fan on/off? Maybe im just nit picking over nothing


I haven't Chris, but it seems plausible to me, if your battery is not charging enough to supply the draw on it. The FI and ignition system need good voltage to run properly, so it would be worth checking out if you are seeing such a fluctuation. You never know with these old machines.
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PostPosted: Sat Dec 10, 2011 11:27 pm    Post subject: Reply with quote

Chris - an alternator load will pull engine RPM down a little just like Air Conditioning will. Late cars have circuits built in that stablize RPM at idle.

You should see about 13.5 V when charging. If you are seeing changes like 12.7 to 15.0 as the RPM increases then I would worry about the VR.

I noticed the other night when it was really here cold that the bus ran rich when cold. It was close to 32F.
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