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'99 500 EFI Powder Special has fast idle

arhcat

New member
Lifetime Membership
Apr 6, 2009
20
2
3
northeast MT
Hello, got a question about my '99 500 EFI P.S. After driving at various speeds for any length of time, my 500 wants to idle at 3000 -3300 RPM. After almost a minute it idles down to 1800 - 1900 RPM. It didn't do this before and showed up some last year, worse this year. Air box is clean, new plugs, clutches cleaned, belt deflection good, clutches are aligned, checked over thouroughly. This sled gets a lot of miles, so bad fuel or gunked up from sitting should't be a factor. :face-icon-small-con What would cause this? Any ideas?
 
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diggerdown

Well-known member
Apr 25, 2004
3,452
677
113
Deer Park Wi.
Usually fast idle is associated with an air leak, but since it idles fine when it is cold or after it has idled a short time I would look at the air temp and water temp sensor. The air temp sensor may be picking up the warmth of the under hood air and leaning the mixture down or the water temp sensor may be telling the engine is cold and needs to warm up. I have some rather lengthy charts on what the ohms should test at for each componet but I have never had the follow though to figure out how to put them on here. You would need to go to a dealer to get the parts anyway, so I would just take them off and have the dealer check them.
 
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