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broomhandle |
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#1
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Member ![]() ![]() Group: Members Posts: 290 Joined: 26-June 09 From: Half Moon Bay, CA Member No.: 10,512 Region Association: Northern California ![]() |
Engine idle raise drop, cold… DJet help.
My 1.7 when started, the idle will go up and down, even for about an hour of driving. After an hour (here or there) the idle stays up and drops for awhile. And then it is fine… but can drop back down sometimes. On hotter days, it seems like it is faster to a normal running idle. I had 4 ideas: 1.)Cold temp sensors, I know there are 2 but I am unsure about it. Or how to test. 2.)Fuel/vacuum. This was my 1st thought, so I have new lines around the motor and the top of the tank. And the injectors have been re-built. but still could be djet. 3.)I have a really old muffler that needs replacing. warms up, can breate... 4.)Air in. (I know ill start some fights here, but it has the oil mess, I swear it can not get enough air) Any ideas? It’s a daily driver, and it is annoying as heck. |
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Rand |
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#2
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Cross Member ![]() ![]() ![]() ![]() ![]() Group: Members Posts: 7,409 Joined: 8-February 05 From: OR Member No.: 3,573 Region Association: None ![]() |
Hunting idle means lean, which probably means vacuum leak below the butterfly. Don't waste your time with the MPS because if there's a vacuum leak there it will run rich, not lean.
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broomhandle |
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#3
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Member ![]() ![]() Group: Members Posts: 290 Joined: 26-June 09 From: Half Moon Bay, CA Member No.: 10,512 Region Association: Northern California ![]() |
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Rand |
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#4
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Cross Member ![]() ![]() ![]() ![]() ![]() Group: Members Posts: 7,409 Joined: 8-February 05 From: OR Member No.: 3,573 Region Association: None ![]() |
Hunting idle means lean, which probably means vacuum leak below the butterfly. Don't waste your time with the MPS because if there's a vacuum leak there it will run rich, not lean. where is this butterfly you speak of. The throttle plate in the throttle body. The round "butterfly valve" that pivots as you open the throttle. Since the throttle is closed at idle, vacuum leaks at idle are being drawn between there and the intake valves. So anything that taps into the intake airstream in that area is a potential source for vacuum leak. In addition to hoses, that means... Throttle plate pins Seal between throttle body and plenum Crack in plenum Seals at plenum to intake runners Phenolic block between intake runners and heads Injector seals ...you get the idea |
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