 1972 1.7L Idle adjust sequence, When & how adjust bypass screw? How get to it? |
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| jjs3rd914 |
 Nov 15 2007, 07:33 AM
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#1
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Member  Group: Members Posts: 124 Joined: 8-August 04 From: Sarasota, FL Member No.: 2,476  |
Just rebuilt 1972 1.7L. What is the sequence for adjusting the idle, specifically when adjust the bypass screw? Is it adjusted before or after the setting of the "pot" on the ECU? All the manuals I have are vauge as to when this is acually done. We will be initally setting the ECU pot with "by the ear and driving method".
Also, the manuals say to remove the air cleaner (oil bath) to adjust the bypass screw. Should all the hoses stay connected? It would appear by removing, the boot has to be disconnected to remove/relocate the air cleaner, thus rendering the air cleaner usesless anyway? Can one get to the screw with everthing in place? If so how? Thanks, jjs3rd914 |
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| TravisNeff |
Nov 15 2007, 10:17 AM
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#2
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914 Guru Group: Members Posts: 5,082 Joined: 20-March 03 From: Mesa, AZ Member No.: 447 Region Association: Southwest Region 
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if you reach in the engine compartment from the passenger side youc an snake your hand around the air cleaner parts and adjust your bleed screw. that pot on the ECU is only good for idle mixture. I would set it in the middle (you can see an indicator on the ecu knob) as that is the factory default setting, then adjust your bleed screw. I am assuming your valves are adjusted and timing is in spec already.
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| 2-OH! |
Nov 15 2007, 02:12 PM
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#3
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Senior Member Group: Members Posts: 552 Joined: 17-October 03 From: Santa Clarita, Kalifornication Member No.: 1,253 |
If I read you right, this is the first start...
You should have adjusted the valves on the bench so they should be pretty close...Valves should be the first step, period... Center the adjustment pot on the ECU (for now)...It's only fucntion in life is to rich/lean the mixture... Then the timing, with both vacuum hoses off the distributor...Stock motor ? Red line in the notch @ 3500 RPM...Not stock, you'll have to play it by ear or get 300 opinions from this board...To set the timing correctly, the motor must be hot, say 180/200 + (oil temp), at least... So on first start, leave distributor roughly in the middle of its range and loose so you can play with it to get started and then smooth out the RPM...Snug down... Re-attach vacuum hoses to the Distributor...Then use the bleed screw to balance it in to say 900/1000 RPM... Any vacuum hoses not attached and secure will cause high RPM, so leave them attached...Fresh air hoses can be disconnected to move the air cleaner...Wouldn't drive it without filter air, but for shop run... 2-OH! |
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| jjs3rd914 |
Nov 15 2007, 10:24 PM
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#4
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Member Group: Members Posts: 124 Joined: 8-August 04 From: Sarasota, FL Member No.: 2,476 |
Thanks for the replies. Yes the valves are adjusted, dwell correct, timing is correct set at 3500, AAR working, PCV vqlve working, and I was able to get my left hand in around the back side of the air cleaner - barely. Will set the idle RPM tomorrow. Motor seem to start and idle as expected. Just was wondering how to set the ECU without the CO meter and what effect it has on the idle.
Thanks for the tips, jjs3rd914 |
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| TravisNeff |
Nov 19 2007, 12:49 PM
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#5
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914 Guru Group: Members Posts: 5,082 Joined: 20-March 03 From: Mesa, AZ Member No.: 447 Region Association: Southwest Region
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turning the ECU knob clockwise for rich, CCW for lean. In the middle of the range is where the factory initially set the mixture.
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