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> Idle Speed and Air Temp/Humidity
StarBear
post Jun 29 2022, 12:46 PM
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As getting ready for the 2022 Northeast Gathering, I'm encountering a semi-recurring idle issue on my 1974 1.8L LJet FI. When outside air is cool and dry, idles just fine at 950-1000 rpm. When outside air is warm and humid, after warmup the idle falls off to barely running. I've just been adjusting the air flow screw (maybe 1.5-2 full turns) to open it. Of course, the reverse happens - if I preadjust the screw it idles near 1800 then settles down to 1100 after the engine gets totally warm (15 mins or so).
I presume (?) there SHOULD be some regulation, perhaps with the ECU or AFM, to monitor air temp and humidity and make adjustments automatically? I didn't have to manually do this adjustment in the past.
The AAR works and tests out fine. Just annoying to have to pull over after running a while and adjust the screw. (IMG:style_emoticons/default/dry.gif)
Your thoughts @Van @Van_B and @Wonkipop ?
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Van B
post Jun 29 2022, 11:24 PM
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On these cars idle is far more likely to climb from metered air than any fueling change. When you mess with the AFM flapper while the car is running you can better understand how small the fuel window is for idle. A bit too little fuel, idle drops, a bit too much, idle drops.

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StarBear   Idle Speed and Air Temp/Humidity   Jun 29 2022, 12:46 PM
StarBear   CHT Sensor? Rpm seems to stay steady if air stays ...   Jun 29 2022, 01:32 PM
wonkipop   only thing i can think of is the other temp sensor...   Jun 29 2022, 05:28 PM
StarBear   Will try cleaning those plugs. Grounds are A+ and ...   Jun 29 2022, 07:30 PM
Van B   Steve, sorry for the delay, I’ve been traveling ...   Jun 29 2022, 11:20 PM
wonkipop   Steve, sorry for the delay, I’ve been traveling...   Jun 29 2022, 11:47 PM
StarBear   Steve, sorry for the delay, I’ve been traveling...   Jun 30 2022, 05:59 AM
wonkipop   Steve, sorry for the delay, I’ve been travelin...   Jun 30 2022, 04:36 PM
StarBear   next time it’s all hot and steamy, you should ...   Jun 30 2022, 07:52 PM
Van B   next time it’s all hot and steamy, you should...   Jun 30 2022, 09:15 PM
StarBear   [quote name='StarBear' post='3012404' date='Jun 3...   Jul 1 2022, 09:54 AM
Van B   On these cars idle is far more likely to climb fro...   Jun 29 2022, 11:24 PM
Van B   Check it all the same. But, it seems to me that y...   Jun 30 2022, 01:28 PM
StarBear   @Van B and [b]@[url=http://www.914world.com/bbs2...   Jun 30 2022, 04:52 PM
Van B   The Porsche manual does a terrible job of breaking...   Jun 30 2022, 04:56 PM
StarBear   The Porsche manual does a terrible job of breakin...   Jun 30 2022, 05:27 PM
StarBear   Ok, looking at Haynes page 177 on fig 9.87 current...   Jun 30 2022, 05:43 PM
wonkipop   Ok, looking at Haynes page 177 on fig 9.87 curren...   Jun 30 2022, 06:03 PM
wonkipop   oh yeah steve. a loose oil cap will make your id...   Jun 30 2022, 06:05 PM
wonkipop   @StarBear i looked through the electrical schema...   Jul 1 2022, 08:51 PM
StarBear   [b]@[url=http://www.914world.com/bbs2/index.php?s...   Jul 2 2022, 06:26 AM
wonkipop   ok @StarBear . i had to keep digging. as i do. ...   Jul 2 2022, 02:18 AM
StarBear   (i leave this with [b]@[url=http://www.914worl...   Jul 2 2022, 06:30 AM
Van B   (i leave this with [b]@[url=http://www.914wor...   Jul 2 2022, 08:32 AM
Van B   Also, still think there's nothing really wrong...   Jul 2 2022, 08:34 AM
StarBear   Also, still think there's nothing really wron...   Jul 2 2022, 09:45 AM
wonkipop   Also, still think there's nothing really wron...   Jul 2 2022, 05:11 PM
Van B   Yeah, you’re a native for sure. Did you buy the...   Jul 2 2022, 10:38 AM
StarBear   Yeah, you’re a native for sure. Did you buy th...   Jul 2 2022, 07:48 PM
wonkipop   Yeah, you’re a native for sure. Did you buy t...   Jul 2 2022, 08:11 PM
Van B   That’s a differ AFM than both of mine. The one I...   Jul 2 2022, 05:30 PM
wonkipop   That’s a differ AFM than both of mine. The one ...   Jul 2 2022, 06:02 PM
wonkipop   i'm just curious about it @[url=http://www...   Jul 2 2022, 06:31 PM
wonkipop   its cold down here today. almost new jersey or mar...   Jul 2 2022, 10:28 PM
StarBear   @wonkipop Yep, we’re just a few miles north o...   Jul 3 2022, 06:45 AM
StarBear   @clayperrine Would you mind chiming in on this w...   Jul 3 2022, 06:58 AM
StarBear   Update: Had a nice 30+ minute run today including ...   Jul 3 2022, 09:27 AM
wonkipop   Update: Had a nice 30+ minute run today including...   Jul 3 2022, 06:06 PM
Van B   Update: Had a nice 30+ minute run today including...   Jul 4 2022, 09:53 AM
ClayPerrine   In reference to the air flow meter, the air temp s...   Jul 3 2022, 02:27 PM
StarBear   In reference to the air flow meter, the air temp ...   Jul 3 2022, 04:12 PM
StarBear   @wonkipop [b]@[url=http://www.914world.com/bbs2...   Jul 4 2022, 09:47 AM
Van B   What I previously described is my method to see if...   Jul 4 2022, 10:00 AM
StarBear   Solved, I think/hope. Did the TB test suggested b...   Jul 4 2022, 12:33 PM
ClayPerrine   Still begs the answer to all our questions about ...   Jul 4 2022, 01:18 PM
StarBear   Still begs the answer to all our questions about...   Jul 4 2022, 01:58 PM
Van B   Resistance figures outlined in the manual are all ...   Jul 4 2022, 03:13 PM
ClayPerrine   Resistance figures outlined in the manual are all...   Jul 4 2022, 03:46 PM
StarBear   Resistance figures outlined in the manual are al...   Jul 4 2022, 05:03 PM
wonkipop   you might have fixed it @StarBear . :beer2: a...   Jul 4 2022, 08:14 PM
Van B   I wouldn’t take those pics of the ‘74 as certa...   Jul 4 2022, 11:21 PM
wonkipop   I wouldn’t take those pics of the ‘74 as cert...   Jul 4 2022, 11:28 PM
wonkipop   @StarBear . just noticed something about your T/B...   Jul 5 2022, 01:19 AM
StarBear   [b]@[url=http://www.914world.com/bbs2/index.php?s...   Jul 5 2022, 05:52 AM
StarBear   Update 2: + did the pin tests in cool garage with ...   Jul 5 2022, 07:24 AM
StarBear   Second test run for 20 min done. Pins 6-9 at 324 ...   Jul 5 2022, 09:55 AM
nihil44   Apologies to the group for posting photos of what ...   Jul 5 2022, 06:00 PM
Van B   Yeah that is definitely the ‘74 AFM right there...   Jul 5 2022, 07:39 PM
wonkipop   Yeah that is definitely the ‘74 AFM right there...   Jul 6 2022, 06:11 PM


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