Thread: Rough Idle help for 1993 USA Range Rover Classic LWB 4.2!

Not much more I could add here, except for a question about idle.
If an automatic, and say, stopped at lights in gear, does the idle speed fluctuate up and down? or stay the same.
Missing to me is where revs stay same, Hunting, where it revs up and down.

Of course if it's not 'hunting' ( as I call it) then disregard.

You know what swissarmychainsaw? I reckon the EFI loom has been tapped into for an ignition powered source. Suggest check where the loom enters the cabin and check the source of power for any user added accessories or repairs.

Originally Posted by Ronski

...snip...

Of course if it's not 'hunting' ( as I call it) then disregard.

No idle hunting, it's consistent at around 650-700 rpm!

Well, I fixed the CEL light issue, and triggering code 45.
The connection of the O2 sensor - at the electrical plug - was not good, and so it was essentially half plugged in. I cleaned up the connector, put a bit of lube for the o-ring and got it to "click" shut.
That seems to have fixed the Check Engine light. Sometimes it IS the simple things.


Still has a stumbly idle, and cranks more that it should to start - cold or warm. So I'll keep after it.
I ordered a fuel pump and filter.
So far I have not thrown any unnecessary parts at the car, so an extra hundred bucks for a fuel pump is something I can live with.

Truth is, I want to start fixing other things, like the shocks and AC!

One thing I forgot to mention:
On the even bank I pulled #8 spark plug wire and tried to start the car.
It started relatively easily and ran fine. Reconnected.
Then I pulled the #6 wired. Started easily and ran find. Reconnected wire.
I did this for the number 4 wire same thing: started relatively easily and ran fine.

All four were the same: pulled the wire off, started the car easily and it ran fine.
How is that possible?

I did the same thing for the fuel injectors:
Disconnected #8 electronic connector to the injector: started and ran fine. reconnected.
#6 Same thing, started and ran fine. Reconnected.
#4 same: Disconnected but it started and ran fine. Reconnected.

Why does this run ok on 7 cylinders?? Maybe even better!

You won't notice any change in revs stopping and restarting engine with one plug disconnected because the Idle Control Valve will adjust the idle speed up as per the ECU, ie either 650rpm or 700rpm (USA)
You have to check with engine idling, before ICV adjusts revs back up.

I know most say don't do it, but I always do. Get yourself a pair of sparky insulated pliers, Real ones, Make sure to get the ones, yellow and orange color at tool shop, Bunnings have them.
Check that they are rated for 1,000 volts. Sometimes come in a pack with 2 similar rated screwdrivers.
I can pull the plug caps easily while engine idling. No worries about getting a boot. This method is better at checking than stopping and starting.

You didn't mention checking number 2 cylinder.?

I used this method to eventually find a faulty fuel injector, yes, a brand new one. I could actually hear a slight change or difference in sound when pulling one plug.
No way could I have heard this by stopping and restarting engine.

Led me to pull off manifold, undo fuel rail and, with injectors still connected to rail, lift as far up as possible.
Then I placed some paper towels below and Yes, cranked engine. Before anyone yells crazy, The coil/dizzy was disconnected and you must be 100% sure no spark, you can imagine. Hmm.
All injectors on each bank spray at the same time, (I didn't know that). I looked at the wet circle created and all were about 100mm, Except for one. it was no bigger that a 50 cent piece.
Swapped some around, and same injector. If attempting this method, check none are dribbling with ignition on before cranking.

This was with all brand new Bosch injectors. I then contacted Piper eng. in UK and got a new set of later Bosch 4 holes ones, a bit expensive but, Fixed.

Hope this helps.

Ford yellow top injectors also were available cheap from the USA about 10 years ago. Not sure now.

One thing noone has mentioned is that the exhaust valves in these can stick due to carbon fouling the stem. Could be an exhaust valve not opening fully.
I would still also be looking at the lifters and cam, as this is a very common problem if oil changes were not regular especially on low mileage V8s.
Regards PhilipA.