The Dreaded Idle Mystery, Idle Me This |
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The Dreaded Idle Mystery, Idle Me This |
Apexster |
Jan 2 2020, 03:05 PM
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#1
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Newbie Group: Members Posts: 8 Joined: 1-June 18 From: Concord, CA Member No.: 22,180 Region Association: Northern California |
Looking for a little insight on the dreaded idle mysteries of a 1974 2.0 914. I've searched the archives for a couple months and tried just about everything.
Valves freshly adjusted. Compression is above 135psi and within 2% on all cylinders. Original D-jet intact with new hoses and all components tested and working. Fuel pressure tested (30-31psi from original 3 hose fuel pump). New plug wires, newly rebuilt distributor, recent fuel filter. I'm about to replace the 20 year old CHT sensor as well. The car revs smoothly and pulls very strong. Engine runs great anywhere above 1200 rpm. Problem is 3 or so minutes after a cold start it drops off the high idle and transitions to a rough idle, like it's running on three cylinders. When I spray carb cleaner in the air cleaner the idle smooths out immediately. Has anyone else come across this issue and perhaps suggest a plan of action to resolve it? (IMG:style_emoticons/default/confused24.gif) Thanks and Happy New Year to All. |
JeffBowlsby |
Jan 5 2020, 12:53 PM
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#2
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914 Wiring Harnesses Group: Members Posts: 8,532 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None |
The MPS is the primary fuel injection sensor to determine injector pulse width (affecting A:F mixture) based on intake vacuum. It could be no influence if it is fully functional and correctly calibrated, or it could be a contributory if not the sole cause of your issues if not.
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