Q: for the L-Jet experts, Idle on the AFM |
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Q: for the L-Jet experts, Idle on the AFM |
914werke |
Jun 15 2022, 06:36 PM
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#1
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"I got blisters on me fingers" Group: Members Posts: 10,066 Joined: 22-March 03 From: USofA Member No.: 453 Region Association: Pacific Northwest |
So I did some searching but couldnt find an answer.
Is there a base setting for the Idle trim circuit on the AFM? Do you start tuning with it set all the way lean & only richen as necessary, or should it be set in the middle of is range at start? Starting from 0 Static time Crack the TB idle screw Warm the eng. till close of the AAR Adj idle at TB Adjust timing Fine tune idle with trim screw. (IMG:style_emoticons/default/confused24.gif) (IMG:style_emoticons/default/rolleyes.gif) |
Van B |
Jun 15 2022, 09:07 PM
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#2
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Senior Member Group: Members Posts: 1,586 Joined: 20-October 21 From: Maryland Member No.: 26,011 Region Association: None |
AFM idle circuit is just an air bypass screw. Manual says you’re looking for 2-3% CO when fully warm at idle. You are correct that the AFM trim and TB idle screw play off each other. But you shouldn’t mess with the AFM screw without a CO meter or a wide band Lambda sensor.
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Van B |
Jun 15 2022, 09:09 PM
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#3
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Senior Member Group: Members Posts: 1,586 Joined: 20-October 21 From: Maryland Member No.: 26,011 Region Association: None |
@wonkipop posted this link a while back and I thought it was a good read:
http://www.itinerant-air-cooled.com/viewtopic.php?t=7761 |
L-Jet914 |
Jun 15 2022, 09:15 PM
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#4
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Member Group: Members Posts: 237 Joined: 24-October 12 From: Davis, CA Member No.: 15,080 Region Association: Northern California |
When adjusting CO you can also see the spec which is stated as less than or equal to on the emissions control label. You will need a CO meter or gas analyzer to set CO at idle.
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914werke |
Jun 16 2022, 01:57 PM
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#5
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"I got blisters on me fingers" Group: Members Posts: 10,066 Joined: 22-March 03 From: USofA Member No.: 453 Region Association: Pacific Northwest |
@wonkipop posted this link a while back and I thought it was a good read: http://www.itinerant-air-cooled.com/viewtopic.php?t=7761 (IMG:style_emoticons/default/agree.gif) QUOTE * Preset Mixture Screw (see Diagram 2C ) Turn regular or 5mm Allen screw CW until it seats (NOTE HOW MANY TURNS). This shuts off the air bypass around the flap. Turn it out CCW 4 1/2 turns. This is the midpoint which gives the best flexibility in the future when you need to do little trim adjustments. This preset may make the engine run poorly. Sorry. Someone has most likely turned it down (thus richening the mixture) in a gleefully irresponsible way to avoid finding vacuum leaks in the past. The answer to my Q: |
Geezer914 |
Jun 17 2022, 09:20 AM
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#6
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Geezer914 Group: Members Posts: 1,418 Joined: 18-March 09 From: Salem, NJ Member No.: 10,179 Region Association: North East States |
2056 Ljet with 50mm Vanagon throttle body. Just read the article on Ljet adjustment. I turned the large wheel CCW 4 teeth to get a reading of 13.2-13.4 Plugs look like this:
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914werke |
Jun 17 2022, 05:21 PM
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#7
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"I got blisters on me fingers" Group: Members Posts: 10,066 Joined: 22-March 03 From: USofA Member No.: 453 Region Association: Pacific Northwest |
Good reference info!
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wonkipop |
Jun 18 2022, 04:11 PM
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#8
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Advanced Member Group: Members Posts: 4,302 Joined: 6-May 20 From: north antarctica Member No.: 24,231 Region Association: NineFourteenerVille |
AFM idle circuit is just an air bypass screw. Manual says you’re looking for 2-3% CO when fully warm at idle. You are correct that the AFM trim and TB idle screw play off each other. But you shouldn’t mess with the AFM screw without a CO meter or a wide band Lambda sensor. missed this thread. @Van B has already linked the info mother lode. other little detail. you are supposed to pull out the hose from the charcoal can at the air cleaner (assuming there is a canister still there). ......for whatever reason CO on a 75 L Jet is much lower than a 74. 0.2 to 1.2% instead of 2-3% on a 74. from factory manual. measurement is before the cat in the cal models and 75 rest of USA did not have a cat. there was a test connection port on the first muffler for those cars. as to why and how a 75 required the much lower CO i dunno. logic tells me that would be so after the cat - thats what a cat does? - but the reading is before the cat. there was a different ECU. (IMG:style_emoticons/default/confused24.gif) since i have a 74 i have never thought further about it. |
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