CAT 580 HIGH IDLE

[rkw]

99 Cat 580 is idling at 3000 rpm. Last time I started it a couple weeks ago it idled perfect. I started it last night and waited for the idle to come down as she warmed up. Never did, it stayed at 3000 rpm even with the engine at normal operating temp.

 

[raceinsnow]

I would check for a mouse nest in the air box first,or something that is holding the slides open in the carbs/throtle bodies.

 

[whitedust]

Check for obstructions like raceinssnow said but 580 chips of that era did some weird things if not below 32F. Start when cold.

 

[matman]

If it has a choke- when it is at high idle try flipping the choke lever a couple of times-if the RPM's drop back then check for binding in those cables or just replace them.

 

[rkw]

Its EFI

 

[roam]

check for cracks in the boots between the throttle bodies and engine..could be sucking air..my cousin burnt up his zr 580 a couple of times because of that

 

[whitedust]

I think it is just crazy chips at high temp but you could be pulling air too.

 

[acbigtwin]

more than likely cracked carb boots. Blew up 2 580's because of it. The AC 580's are famous for that.

 

[rkw]

Thanks Roam and Acbigtwin, you guys were right on.
I did the carb clean test and the RPM changed.
Looked real close at the rubber throttle body boots and both were cracked. R n R boots, problem fixed. Thanks again, I owe you a beer eh

 

[dopp]

Craked carb/injector boots.
with engine running spray carb cleaner around boots.idle will change if there are cracks
this is a common problem