Rover 4.2 Efi idling issue

[neilw]

Hi

A while back I posted about issues with my 170k 4.2 Range Rover LSE.

The last few months have been spent rebuilding the top end, new cam etc.

Engine sounds great but I've had some issues related to fast idling and hunting

I've spent the last couple of weeks chasing down vacuum leaks and have the timing sorted, think I'm on top of the hunting problem.

There is still an issue getting it to idle, currently it idles at 1100RPM. I've also found if I depress the throttle (either pedal or at throttle body) the revs increase as expected, the throttle cable returns to the original position but the revs remain high and start to climb.

I have an ECUMate which is not showing any faults.

ECUmate readings at idle are:

LamA - 131
LamB - 162
TPOT - 19% @ 0.97V - thinking this is little high for idling ??
Idle - OFF

AFM 2.34
Tune: Blue with Cats

It's the Idle being off that's the confusing bit. There's no error reported with the Road Speed Transducer. With the TPOT always running high am I right in assuming it will never go into idle mode?

I have attempted to adjust the idle control (following the instructions in the ECUmate manual), but this does not make a difference.

So, in conclusion ECUmate not showing any faults, ECU won't go into idle mode (possibly because of a high TPOT reading).

Before I put another £100 into a new throttle Potentiometer I'm wondering if there's anything else I should be looking at. Would a TPOT problem cause the issue of the revs staying high once the throttle is depressed?

[ChrisJC]

I think that the idle speed is lifted under certain conditions, like the a/c being on. So maybe worth checking the various inputs to the ECU of that nature.

For the throttle pot - you could try unplugging it and see what the engine makes of that!

Chris.