fast idle help please

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flyingbanana

Member
Posts
92
Location
Southampton england
I've been told that this switch on the plenum chamber is causing my problem on start up it revs high for
About 4 seconds then drops down any help at all RR 3.9 1990. please
Andy
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It is supposed to do that to a certain extent though (idle adjustment every 2 seconds). It prevents stalling in drive or when you switch on air con etc. If you aren't experiencing excessive fast idle problems pulling up at junctions or engaging park with a warm engine it may be normal.
 
flyingbanana said:
It goes to about 2000rpm bit to high I think
Click to expand...

Yes to high, a leak in a vacuum pipes into the plenum will do that, its shows the ecu is trying to compensate.
When I fitted a Janspeed free flowing exhaust my idle speed went up to 2000rpm for a minute, but thenwent back down to normal thanks to the ECU readjusting so maybe a leaking exhaust maybe a reason for the high Rpm.
An iffy idle control valve could give u difficult starting but if only takes 5 mins to remove clean and replace if you suspect it.
 
Certainly sounds like an air leak.

Have you checked all rubber hoses? Mine had a perished hose leading to the cruise control vacuum unit. It did similar things, but we serviced the whole thing so it went away, but I know if it draws extra air it will rev higher.
 
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