Low idling woes

Hi all!

Last week I got my first ever Range Rover. It's a 1995 4.6 HSE in dark grey metallic (looks black most of the time!), is automatic and has done 82,000 miles.

When I looked the car over, it had a slightly low idle, which made it sound a little rough, but didn't seem to indicate anything too drastic.

I've done about 300 miles now and what seems to happen is that every now and then, the car will drop the revs so low when stationary, the car decides to stall - typically when coming to a stop at junctions!

After it has done it once, the car will pretty much do it every time you stop from there on, until I finish getting to where I'm going and let the engine cool. Once cold, it's *usually* ok again (but not always)

So, in short, when the engine is cold, it does idle very low (and I mean 400rpm or less) most of the time, occasionally stalling. When the engine has warmed, it seems to want to idle even lower, increasing it's tendancy to stall (but again, not always)

I don't have any manuals or schematics yet, nor do I yet have an owners manual (all of these things are on order!)

So, with that in mind, can you kind people please point me at where to start looking and what to adjust etc? I'm just afraid the missus will take the car out and end up getting stressed if it starts playing up for her!!!

Thanks!

Gaz

It needs a session on Testbook to see whats going on.

So it's not a common, generic issue then? Nothing I can test for on my own? What should the resistance of the MAF be, for example? I'll be checking oils, sparks etc over the weekend, I just thought there might be an established list of things to check for such symptoms.

dragon3.6HSE said:

So it's not a common, generic issue then? Nothing I can test for on my own? What should the resistance of the MAF be, for example? I'll be checking oils, sparks etc over the weekend, I just thought there might be an established list of things to check for such symptoms.

Click to expand...

Testbook isn't the be all and end all and there's a fair bit you can do without it, EFI on the 4.6 is an easy system to diagnose without T4

First off, do a service, new plugs, air filter, fuel filter etc, check HT leads for arcing out (usually you'll see sparks jumping to the rocker covers).

check all your vacuum/breather hoses for splits/damage.

Check idle air control system (throttle body area) for leaks and make sure its all free and not gummed up with crap.

check for air leaks from the inlet plenum (where the 2 halves join), better still, remove the top half and clean it out. On refitting, seal it with a small amount of instant gasket.

check the pipe from MAF to throttle body for any splits/damage.

The fault you describe does sound like an air leak, when cold the EFI richens the mixture, the same sort of thing as a choke on a carb engine, so an air leak wont really affect it till its warmed up, when warm, the fuel/air mixture is leaned, excess air caused by an air leak will make it stall and idle too slow.

A blockage in the idle air control will also have the same effect.

Cheers for the replys. My workshop manuals and owners manual arrived at the weekend, so ready to crack on and see whats what with this beast