RoverV8 3.9efi Idle question

h042271 · Winch Assistant Joined: 30 Aug 2004 Odometer: 95

OK LPG experts it's over to you...Discovery 3.9efi, the idle is all over the place. Basically the idle can range from stalling to 1800 rpm on both petrol and gas. Cannot define a pattern other than it happens more often when warm.
So far ....changed the plugs, leads and dizzy cap. These were being done anyway as the old ones were looking iffy.
After reading on this site pulled the valve on the back of the plenum chamber and cleaned. No effect. Looked over the hoses for leaks and can't find any obvious ones.
I had to remove the charcoal canister input from the petrol tank filler when i moved the tank so this is open to atmosphere but it would only have been pulling excess fumes from the filler so can't see that making a difference.

Any ideas welcome

webber1982 · Posted: Sun Jan 28, 2007 6:38 pm Post subject:

if it does it on petrol as well as gas then it is not a LPG fault sounds like the idle speed control valve otherwise known as the idle air control valve. also the air flow meter will cause this if it has one if not the map sensor.

h042271 · Winch Assistant Joined: 30 Aug 2004 Odometer: 95

Thanks. Will start there then i guess. I think the guy i got the car from has a spare airflow sensor so will give that a bash first

11% ORANGE ROVER · Posted: Mon Jan 29, 2007 9:19 am Post subject:

If it is a hotwire AFM, give it a really thourough clean. Use isopropyl alcohol asnd reallly flush it through. It made a massive difference to a mates 3.9 idle and only cost him a few quid.

eBay sells AFM cleaner, but not sure if that is better or worse than the alcohol we used.

h042271 · Winch Assistant Joined: 30 Aug 2004 Odometer: 95

I'll try that first.....once tried to get a set of injectors out of a Mercedes Vito head...they are a complete bar steward. Went on the net and all but one guy said "going to cost you Â£3000.00 for head removal and broken injectors. Went to Merc they said the same. Found a post that said "coat in Mr SPAM oven cleaner overnight to break down the carbon that holds the injectors in". Well Â£7.50 for oven cleaner and 4 new washers the job was good.......All power to the Forum....off to the shed

h042271 · Winch Assistant Joined: 30 Aug 2004 Odometer: 95

fixed it. pulled the transfer box speed sensor and cleaned...pulled the throttle position sensor and cleaned. Cleaned the hot wires as per post above . Checked the breathers all OK. Found a cracked O ring under the gauze filled thingy on the right hand rocker cover that connects to the breather. Will now idle on gas and petrol. Thanks for the advice

webber1982 · Posted: Sun Feb 04, 2007 6:15 pm Post subject:

glad Ur sorted bud.

11% ORANGE ROVER · Posted: Mon Feb 05, 2007 9:07 am Post subject:

Great news, I bet you're chuffed?

h042271 · Winch Assistant Joined: 30 Aug 2004 Odometer: 95

Well happy..... cheers