Unstable at idle speed

What are the causes may be unstable with RPM?
875 ± 50
I read many forums about this problem, but I have not found the correct and precise answer. Lots of questions and recording the YOUTUBE, but never the right answer.
Does someone who is a member of this problem has an answer.
Thanks.

My Freelander sometimes does this as well (same engine) and I think its possibly the IACV - Idle air control valve or stepper motor possibly not closing properly - just a guess though, I have never investigated further

One of the common causes is the Idle Air Control Valve. (IACV)

It gets gummed up with carbon deposits and doesn't open/close smoothly.

I cleaned ours. There is a How to in the How to section. :broon:

MY OLD BLUE HAD AN INTERMITTENT TICK OVER PROBLEM

it would be fine then some times it would wander all over the place then cut out
new ivac valve new throttle position sensor fitted and coolant sensors , then new cam position sensor but still had the same problem

ended up having a new ecu :omg: and that sorted it for the new owner :yesnod:

I used David and Clives' guides to clean mine last week and it has been noticably better at idle this week.

IACV - Removal, cleaning and replacing the valve.
IACV - Replacement guide.

What I also did from 'reading the net' was to reset the ECU (engine control unit).

Resetting the IACV.
Reason for resetting - The throttle has a sensor on it (TPS - throttle position sensor) that sends a 'voltage' corresponding to its position to the MEMS unit (Modular Engine Management system). This tells the computer the current position of the throttle ( ie; How much throttle you are applying) This enables the MEMS unit to calculate the correct operating parameters ( Fuel / Air mix etc).

It is important the MEMS unit knows the absolute min and maximum input voltage it will see on the full extent of throttle to enable it to correctly know the current position it's in. We do this by resetting it.

How to reset the IACV.
If you find that the idle speed is 'hunting' or high, try resetting the throttle position sensor (TPS). Here's how you do this:-

Warm up the engine to its normal operating temperature (the engine requires extra air and fuel when cold). This is actually what the IACV - idle air control valve manages.

Switch the ignition to position 2 so that all the lights dash lights come on but don't start the engine up.
Press the accelerator down slowly to the floor 5 times in 30 seconds.
Wait for 15 seconds.
Turn off the ignition.
The TPS has been re-set and the engine can now be re-started.


You could give this a try before you clean or replace the IACV /Stepper motor. But you should also do it after you have done either of those two jobs as it apparrently allows the ecu (engine control unit) to re-learn.

Feel free to put me right, if I'm incorrect on this procedure. I don't think that it will break your car if you try this. But if it does, the usual disclaimers apply. :lol:

what leigh has put is correct :yesnod:

however some times on these old cars oher things come along and bite

some times its worth having a spair that works so you can eliminate that part ect

In the first year ago, I cleaned the throttle body and IACV. Gave rezutate. But the problem appeared after a year again. Again, I cleaned everything, but without the desired result. A week ago I put new IACV, but the problem is the same. Of course I did and reset TPS, but it did not help.
What are the following comments and suggestions. It's not as "horrible", but it annoys me terribly. :bang: :rant:

If the throttle body is black plastic, it can warp over time and give random idling issues. Changing to an aluminium one could work (it worked for me!)

From the service records of my early F, the plastic body was changed because it was sticking (car would not idle!) and they appear to have fitted an alloy one, but dont know what size (assume 49mm standard) this was done at 55, 400 miles at a cost of £240.00 ( late 2004) wot a lot of money :slapme:

bryan young wrote: ..... they appear to have fitted an alloy one, but don't know what size (assume 49mm standard) this was done at 55, 400 miles at a cost of £240.00 ( late 2004) wot a lot of money :slapme:

The throttle body will be 48mm standard or 52mm, see this thread here on the T-Bar for more advice on throttle bodies, how to identify which one you have and modifying them.

£240 :omg: it's is only a 15 min job for £240 I would expect a platinum coated one :lol:

PQD44 wrote:

bryan young wrote: ..... they appear to have fitted an alloy one, but don't know what size (assume 49mm standard) this was done at 55, 400 miles at a cost of £240.00 ( late 2004) wot a lot of money :slapme:

The throttle body will be 48mm standard or 52mm, see this thread here on the T-Bar for more advice on throttle bodies, how to identify which one you have and modifying them.

£240 :omg: it's is only a 15 min job for £240 I would expect a platinum coated one :lol:

Have to agree! It really is a simple job, even for a novice. I picked up a 52 mm one on eBay (new) for about £85 and fitted it myself.

Throttle body on my car is 52 mm aluminum DELLORTO.