 Idle Speed and Air Temp/Humidity |
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| StarBear |
 Jun 29 2022, 12:46 PM
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#1
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Advanced Member  Group: Members Posts: 2,071 Joined: 2-September 09 From: NJ Member No.: 10,753 Region Association: North East States 
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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 |
Jun 29 2022, 11:20 PM
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#2
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Senior Member Group: Members Posts: 1,618 Joined: 20-October 21 From: WR, GA Member No.: 26,011 Region Association: None
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Steve, sorry for the delay, I’ve been traveling for work and forced to do things like socializing after hours lol…
Anyway, next time it’s all hot and steamy, you should grab hold of the throttle body and try to force the butterfly closed. If the idle drops back to where it’s supposed to be then I think you may have a worn TB that’s not seating and reveals itself when the metal heats and expands just enough to not seat properly. |
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| StarBear |
Jun 30 2022, 05:59 AM
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#3
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Advanced Member Group: Members Posts: 2,071 Joined: 2-September 09 From: NJ Member No.: 10,753 Region Association: North East States
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QUOTE(Van B @ Jun 30 2022, 01:20 AM)  Steve, sorry for the delay, I’ve been traveling for work and forced to do things like socializing after hours lol… Anyway, next time it’s all hot and steamy, you should grab hold of the throttle body and try to force the butterfly closed. If the idle drops back to where it’s supposed to be then I think you may have a worn TB that’s not seating and reveals itself when the metal heats and expands just enough to not seat properly. I’m actually having the reverse problem - when hot and humid the idle drops. Sort of as if the less dense air and added moisture yields less O2. I checked the LJet guide and 74s don’t have the air temp sensor in the AFM. |
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Posts in this topic
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
wonkipop
Steve, sorry for the delay, I’ve been traveling... Jun 29 2022, 11:47 PM
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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