Causes for idle bounce? Anyone? Anyone?

[silverbullett]

my idle slowly bounces from 800 to 1050 rpm all the time. what gives. some say its normal dsm stuff. any feedback hlps. thanks.


98 gst

evo3big16g
greddy fmic
blitz sbc id
stock fuel system
3" cat back
kn intake
new tps
new iasc

 

[kenamond]

I'd guess idle surge. Never had to deal with it myself, but I'm sure a search would give you all you need to know.

 

[silverbullett]

Thanks dude.

 

[El Cuervo]

Does it happend after its fully warmed up?? While at a stop light??
Its usually due to vacume leak, not connected or false connection of the mass air flow sensor at your air filter. Biss screw gasket ring is shot or not sealing correctly. ISC motor behind throttle body.

 

[silverbullett]

yeah only when its fully warmed up. it happens at stoplights. it goes away if i drive like a bat out of hell but, if im just cruising, it comes back, drops to 450 rpm then slowly back up to 800.
im gonna check the isc motor. thanks.

 

[schoffs4]

Check tb plate gaskets

 

[silverbullett]

good idea thanks.

 

[kahl23]

I had the same problem and it turned out that the ISC was bad. Unplug the battery and when you plug the battery back in, you should hear the ECU cycle the ISC to calibrate it. If you don't hear it do this, well then you know it's bad. I had it happen a second time, but it turned out that the ISC harness connector had worked its way out. Two possible causes for you to check.

 

[blcknspo0ln]

http://www.vfaq.com/mods/wayback/BradBauer/engine/surge.html