fast idle help please

[flyingbanana]

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

 

[Saint.V8]

That is the idle control valve.....they can stick.

Not sur ehow best to clean, so do some research on how to clean the rover V8 idle air control valve.....

 

[cooltide]

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.

 

[discool]

Just as it should, starting from cold rpm goes up to around 1200 for a couple of seconds or so, the drops to 1000 then again down to arround 750 all that takes place in 5 or 6 seconds.

 

[pete1987RRC]

Take it out, good spray with carb cleaner, wipe with clean rag, put back in.
Service item.

 

[flyingbanana]

Just as it should, starting from cold rpm goes up to around 1200 for a couple of seconds or so, the drops to 1000 then again down to arround 750 all that takes place in 5 or 6 seconds.

It goes to about 2000rpm bit to high I think

 

[discool]

It goes to about 2000rpm bit to high I think

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.

 

[flyingbanana]

Don't know if this has any bearing in my issue Any help please on this warning light that apered last night what's its for I've no book RR classic 1990 v8

 

[Doo]

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.

 

[cooltide]

Don't know if this has any bearing in my issue Any help please on this warning light that apered last night what's its for I've no book RR classic 1990 v8View attachment 104865

ECU fault. Disconnect battery for 1min to reset or have it diagnosed.