1997 Plymouth Voyager engine races at high idle when starte

1997 PLYMOUTH VOYAGER
128,000 MILES • 6 CYL • FWD • AUTOMATIC
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RDMX2
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I recently changed the transmission and my engine that ran great started to miss. I removed the upper intake phlenum to change the rear spark plugs and when i put it back togather the engine shoots right up to 4 grand at an idle. I have looked for anything that I might have missed on assembly but I can't find anything. I disconnected the TPS, no change I disconnected the IAC, nothing. There are no trouble codes, but I haven't let it run very long, just long enough to see where the idle is and shut it down. Please help, I have seven kids and getting them around is getting very hard.
Jun 14, 2009 at 1:18 PM
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LEGITIMATE007
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first lets try and do a throttle body cleaning and throttle plate cleaning, the plate may be stuck ajar, also do a vacuum leak check by misting some brake clean at the vacuum hoses and pcv connection,(could be disconnected too) if the idle changes then thats where your leak is, see it hasnt run long enough to get a check engine light so we really dont know if it is a vacuum leak thats why I say do those couple of things.
Jun 14, 2009 at 1:55 PM
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CARADIODOC
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The rear plugs are replaced from underneath and are quite easy to get to. When you removed the plenum, did you install a new gasket? Saw one once that developed a 1/2" long gap right in the front where the gasket cracked. It had never been taken apart, but that gap was big enough to cause the engine to idle at over 3000 rpm.

If the gasket is new, look for cracked or disconnected vacuum hoses, but they won't usually cause the rpm to go that high.

caradiodoc
Jun 19, 2009 at 10:40 PM
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