V8 Discovery - Suddenly Running Lumpy & Changing Autobox

[Ian Seale]

Hi,
Last time I used this site, the help and assistance was blinding, so fingers crossed.
1) Lumpy running. Last week, after prolonged standing in stop-start traffic at the Blackwell Tunnel, my V8 Disco (3.9 EFi) started to cough and splutter on tick-over. With this being an Auto too, you can imagine how tricky it was keeping the revs high in neutral and slipping it into drive as complete wakners dived into the spot in front of me because I'd left half a millisecond gap, and find I can only shift forward 6 feet - then heavy on the brakes. Not to be recommended.
Back to the problem, I managed to get home and it ran fine with the revs up and travellng at sensible speeds, but kept running lumpy (sounding like it was over choked) as soon as it got near tick-over. Also trying to accelerate when it was lumpy required a very delicate touch on the throttle.
Air filter and timing are fine, as are the HT leads, rotor and cap - all new within the year/6,000 miles.
I did change the spark plugs, as precaution, and the ones that came out were a little on the sooty side, but all dry, and not oily.
I've just stuck some injector cleaner in the tank as precaution too, but it's too early for that to have any effect.
Haynes aren't much use, but I read somewhere else that there could be an airflow sensor problem.
Can the airflow sensor get dirty?
Can it be cleaned?
How?
2) This is a little easier, how to drain and replce the oil in the automatic gearbox. Unbelievably, Haynes reckon its a Land Rover dealer job - draining oil? Come on chaps. Thing is without any form of description as to where the drain plug is I'm stumped.
All help very gratefully received.
Cheers,
Ian

 

[^neo^]

Only way to clean the air flow meter is with a tin of brake cleaner. Does sound like it could be your problem. Other thing to check for while you're there is any air leaks on the manifold / breather pipes.

Not sure about gearbox oil change on an auto, but manual ones have a bolt on the bottom to drain, and an allen head bolt for refilling

 

[Ian Seale]

Neo,

Cheers for that.
Not come across 'Brake Cleaner' is it similar to Meths i.e cleans and evaporates without any residue - got pints of that in the drinks cupboard.

There's plenty of bolts on the bottom of the auto box that could be drain plugs, hopefully someone else might know.

Thanks very much for your help.

Ian

 

[^neo^]

It's just an aerosol. Can buy it from halfrauds for a couple of quid.

If haynes says its a dealer only jobby then perhaps it hasnt got a drain plug........ more likely to need sucking out from the top. Doubt even haynes would tell you to take it to the stealers for a box oil change

 

[Belle427]

i would say that if there isnt a drain plug or sump type plate on the box to remove then it gets flushed out somehow using cooler lines or similar

 

[davieboy]

what year of disco?? does it have a dipstick for the autobox? being a 3.9 i would asume its a 300 series (i.e late mk1 disco.) if so it has a drain plug on the g/box sump pan. if it has a dipstick fill it to the cold fill level on the stick. if not there will be a filler/level plug on the front of the g/box sump. fill till fluid runs out of hole.

p.s. NEVER use brake cleaner on an air flow meter. use a proper carb cleaner spray. they are totally different things. the brake cleaner does damage to the electonic components.

 

[Ian Seale]

Davieboy,

Thanks for the tip, about Brake Cleaner.
I actually picked up you post after I'd had a though along the lines of "wouldn't carb cleaner be better" and bought a can of the Wynns stuff today

Yes, it does have a dip stick, so I'll have a good look for the drain plug.
Haynes says to check level warm at idle, but I've got the box oil capacity, so if I can drain it, I can stick in a 'safe' amount and gradually top up.
I still can't work out why Haynes refer it as 'Dealer Job' though - very strange.

cha427,

Thanks for that tip, if I can't find a drain plug (and I don't want to go unbolting anything unless it's obviously a drain plug), sucking the stuff out through the top and syphoning it out may be a good idea. Better pucker up.

Cheers,

Ian

 

[jayzee]

Take off complete sump with oil in it, dispose of old oil then clean out sump & strainer.

 

[Ian Seale]

Jazee,

Thanks for that tip. Sounds messy.
I guess the sump pan will be obvious from underneath.
I just didn't want to go undoing bolts and go-wheels came falling out.

Cheers,

Ian

 

[davieboy]

iirc, gearbox sump held on with six bolts holding metal brackets into a lip. unbolt the dipstick tube (catch the fluid!) and undo the six bolts. sump pan should come off. there is a filter inside that should be replaced. on some discos i think you may have to drop the g/box crossmember.

you will need a new gasket for the sump pan (rubber) a filter and a filter o-ring. available from your friendly landrover dealer.

as i say thats if i remember correctly. may be thinking of the range rover, but i don't think so

dave

 

[Ian Seale]

Davieboy (& others),

Like I said at begiining of this post "Last time I used this site, the help and assistance was blinding".
STILL IS!

Thanks Gents!

Ian