Idle speed adjustment

Rangie V8 · Post by **Rangie V8** » Wed Feb 15, 2012 3:16 pm

Hi all.
Have had a complete engine re-build.
And now it's been started 7/8 times, I still need to get the Idle speed Right!
RANGE ROVER 3.5 Efi from 1986.
First starts were running at around 1200rpm.
Then after a few miles she went down to about 1000.
Can't be 100% sure RPM counter is spot on though!
Should I be looking for about 6/700 Rpm?
And which is the best way to get this other than just turning the adjustment screw? Is there anything else I need to adjust? As I'm scratching my brain a bit!
Thanks!
Colin

DaveEFI · Post by **DaveEFI** » Wed Feb 15, 2012 3:48 pm

Assuming flapper injection. it has an extra air valve which speeds up the idle when cold, and gradually reduces it as it warms up. It is not ECU controlled - it uses coolant temperature and a heating coil acting on a bi-metal strip.

So make sure the engine is fully up to temperature before setting the idle speed. You should also make sure the throttle butterfly is closing properly - it should be set just cracking open with about 2 thou gap between edge of the disc and the body.

Also make sure the idle CO is correct at 1.5-2%

Rangie V8 · Post by **Rangie V8** » Wed Feb 15, 2012 4:16 pm

Nice one Dave, thanks for that, will give it a try!
And then get back on it!

ChrisJC · Post by **ChrisJC** » Thu Feb 16, 2012 7:53 am

The idle speed is NOT set by the throttle butterfly, it's set by the bypass screw, which is the large recessed screw next to it. The butterfly should be completely closed at idle. Hence the importance of having the butterfly set up properly.

I suggest you remove the idle screw and check it's all clean in there.

An air leak will give an erratic idle too.

Chris.

DaveEFI · Post by **DaveEFI** » Thu Feb 16, 2012 9:03 am

ChrisJC wrote:The idle speed is NOT set by the throttle butterfly, it's set by the bypass screw, which is the large recessed screw next to it. The butterfly should be completely closed at idle. Hence the importance of having the butterfly set up properly.

I suggest you remove the idle screw and check it's all clean in there.

An air leak will give an erratic idle too.

Chris.

If you look at the later TI from Land Rover, the butterfly is set as I said just cracking open. Not fully closed. And have seen a few of these in practice

I've come across ones where they have obviously been altered in an attempt to set the idle, so it should be checked first.

ChrisJC · Post by **ChrisJC** » Thu Feb 16, 2012 10:08 am

I think the idea is that the butterfly should be as close to fully closed as possible without jamming closed.

Chris.

DaveEFI · Post by **DaveEFI** » Thu Feb 16, 2012 10:23 am

ChrisJC wrote:I think the idea is that the butterfly should be as close to fully closed as possible without jamming closed.

Chris.

Either that or to prevent wear.