1200-1400rpm tickover...............?

[JMF894]

Hi, my 450 has always idled on the high side and recently it has risen to around 1200rpm once warm. This was after I recplaced the coolant temp sensor. Today I disconnected the 9th injector and now tickover once warm is as much as 1400rpm.

Ideas guys?

Jimbo

[TVRleigh_BBWR]

Running very rich can make it idle worse, so now it's running better without the 9th this is causing it to idle faster, the idle speed may have been raised as a cheap fix for the car not running correctly, so may just need adjusting down again, I prefer a slightly higher idle to protect the camshaft though.

[350Wedge]

Have you cleaned the stepper motor recently (screwed into back of plenum normally)? Had similar on my 400 and cleaning it up solved the problem. Takes 2 mins to do!!

[Number 7]

350Wedge said:

Have you cleaned the stepper motor recently (screwed into back of plenum normally)? Had similar on my 400 and cleaning it up solved the problem. Takes 2 mins to do!!

It's a flapper I believe.

[JMF894]

350Wedge said:

Have you cleaned the stepper motor recently (screwed into back of plenum normally)? Had similar on my 400 and cleaning it up solved the problem. Takes 2 mins to do!!

No I haven't chap. Will sort it and see what happens cheers

[Number 7]

JMF894 said:

No I haven't chap. Will sort it and see what happens cheers

If it is a flapper (thought you peviously posted it was) then you won't have a stepper motor, just an overrun valve. No point in removing it to clean it, as it won't affect idle.

[JMF894]

Ahh i see. Yes it is a flapper. Thanks.

[adam quantrill]

Check for air leaks into the plenum which allow more gases in bypassing the throttle. E.g. the EAV, vacuum pipes, etc.

[adam quantrill]

Echo the timing, mine is supposed to be 17BTDC and it was only 9 when I checked it. When I advanced it, the idle speed rose from about 850 to 1000. So if yours is too far advanced, you might see the same effect.

[Wedg1e]

Well the cold start (9th injector) should really be taken out of the equation as it has sod-all to do with running the engine. It's controlled by the thermo/time switch and if its's firing when it shouldn't it's either stuck open or the t/t switch is shorted. Even so, it'd be tending to add lots more fuel for no more air so I'd expect it to be spluttering like Gillian Taylforth and smelling rich.

It's obviously just occurred so is unlikely to be the idle speed or mixture screws - they don't just jump out of adjustment.
Throttle plate not closing properly would certainly be an option: the engine won't know why it's open so will just fuel and fire acccordingly. Frayed throttle cable perhaps?
Air leak: again a possibility but unless you've been working on the injection system, would seem an unlikely spot-change.
Sticking AFM flap a possibility but without corresponding throttle opening would again tend to run rich.