Fast idle trouble shooting


Staff member
2011 Honda FN2
My car suddenly developed a 1800 idle at the last event and i worked thru the following stages to track down the culprit.
1 checked all hoses for leaks/cracks etc for the possible source of a vacuum leak.
2 removed the inlet air control cleaned and replaced it .
3 installed new IAC.
4 Unplugged the electrical wires from the ISC.
5 Unplugged the TPS

None of the above lowered the idle \B :mad:

Drove the car to a workshop that had a smoke machine as did not want to remove the inlet manifold (a real PITA ) if the gasket was not the fault and smoke came out from around the top and bottom of the throttle butterfly shaft.

Removed the TB and sent it away to be recoed and reinstalled it and still have the high idle :mad::mad:
Disconnected the ISC hoses and plugged them started the car and suddenly I have a 900 rpm idle :D

So it appears that there is an electrical gremlin that is preventing the ISC fron operating correctly.
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My new hi tech mod cold start mod is a paddle pop stick placed between the throttle stop to hold the throttle open enough until it warms up and settles down to the app 900rpm warm idle |B :)

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