Thread: Intermittent rough idle 89 3.5 efi RR.

Pete, before buying another air flow meter remove the wiring plug and clean both lots of plugs and receptors with electrical contact cleaner, if the the male pins are split, use a small flat bladed screwdriver and gently open them up a mickey, connect and diconnect a few times and see if that solves the problem, sometimes a loose fitting or dirty plug can cause this problem.
Also (if fitted) check the Idle Air Control valve on the back of the plenum chamber is bolted up tight, remove it and clean oil and carbon deposits off plunger valve and it's seat, do the same to the electrical plug as you did to the air flow meter.
Come back with the results here and let us know if it helped or not, Regards Frank.

Thanks for the reply Tank, I have already cleaned the contacts on the air flow meter plug twice and also the contacts on the ecu.
When you mention the Idle Air Control valve, are you referring to the Extra Air Valve?
On my 3.5 that is located at the front left of the plenum chamber.
I can't find any mention of an Idle air control valve in my workshop manual.
There is also a solenoid operated air valve, which sits under the air inlet to the plenum chamber.
I've never had to deal with these bits before, so a learning curve for me!
Cheers, Pete.

The flapper 3.5's use a large bypass type idle air control solenoid mount under the fuel rail and heater pipes on the rh (from drivers seat) side of the intake manifold at the front of the engine. it has a 1/2" id vacum hose going to each side of it and an electrical connector for the solenoid. Your could spray some throttle body cleaner in there but in my experience they bypass valves dont give much drama.

Did you use a genuine rotor cap? Several of the more experirenced and knowledgable members on here have suggest that the non genuine buttons will cause poor idle and hard starting.

I have tried every concievable thing on my wolf 4.6 to fix the incosistant starting and dodgy (at times) idle and this is the only thing i havent touched, and i still haven't fixed the problem.

Thanks Lucas, sounds like you have been having a bugger of a time trying to get this sorted as well...that's why I am reluctant to pay a mechanic big $ to go through the same process.
Yes I have just put in a new genuine Land Rover rotor arm, new Lucas distributor cap, new quality leads, new plugs and coil.
I was hoping this might solve things, but no joy yet.
The valve I think you are referring to in my workshop manual is called the extra air valve, at the front of the plenum. Is that correct?
I have not worked on these before, so it's ok to spray throttle body cleaner in there?
I also noticed an electrical connector at the bottom rear of that, I might try and give those connections a clean as well.
Cheers, Pete.

yeah thats the extra air valve. That provides a metered amount of air to maintain idle speed. Might pay to remove the hoses and make sure they arent split, perished or choked up with carbon. I would also clean the port on the throttle body that supplies the air to the valve and well as the port on the plenum where the air is introduced. Probably pay the clean the throttle body with cleaner as well. Have you checked for vacum leaks? This can cause erratic idle as well

Where are you PeterH? looks mighty snowy in that picture?

Certainly not snowy here, it's been in the 40's the last couple of days.
I'm in Melbourne, but that photo is from one of our ventures up in the snowfields..I think that one was taken at Mt Hotham from memory.
The Rangie loves it up there, never misses a beat!

Thanks for the tips, I'll check all that and let you know how I go.
Cheers, Pete.

Just had a quick squiz in the manual it, i says you should have 12+ve at the plug for the idle bypass valve with the key on. It also states that you should have 33ohms across the terminals of the valve with the wiring disconnected.

Originally Posted by PeterH

Certainly not snowy here, it's been in the 40's the last couple of days.
I'm in Melbourne, but that photo is from one of our ventures up in the snowfields..I think that one was taken at Mt Hotham from memory.
The Rangie loves it up there, never misses a beat!

Thanks for the tips, I'll check all that and let you know how I go.
Cheers, Pete.

Pete, what Lucus says is correct, my experience is with my 93 Disco, earlier ones like yours are as Lucus says, I would also check all of the PCV hoses and fittings for carbon build up, I have seen fittings completely blocked with carbon buildup, clean out the flame trap/filter on the front of the drivers side rocker cover, Regards Frank.