2004 Disco turns off in reverse

Hey guys and gals,

I have a 2004 Disco HSE that sometimes decides to turn off when I select reverse. This happens kind of hit and miss and sometimes it won't turn off completely, but rather rumble (RPMs drop) and then it catches itself and its fine. I can go weeks without it doing it. Weather doesn't make a difference, temp doesn't make a difference, leaving my foot on the brake or taking it off doesn't make a difference...

I've thought at times it feels like a fuel issue, but why would it only happen when I select reverse? Air filter, spark plugs and wires are pretty new, I clean my throttle body on the regular. This has been happening for close to a year now without any other issues to track down.

Anyone else run into this?

I have a '99 DII with the 4.0L Thor engine, and I have not experienced anything like this. The 4.6L was a transplant for '03-'04, so the engine management is completely different.
That being said, there are a few ideas I have, based upon my own experience with other vehicles that I have owned. First, fuel injectors. If the fuel injectors are not working at optimal effiency, when you put the Disco in reverse and the revs drop, it may not be allowing enough fuel in the cylinders. Second, the fuel itself. If brands of fuel are switched on a frequent basis, everything changes. The degree of detergent, composition of fuel, whether or not the fuel is oxygenated, all have an effect on its ability to burn clean in the engine. Third, the air sensor. If that little gizmo is misreading the airflow and cuts it off, so much for ignition.
Again, these are just ideas of mine. It could be any number of individual things, or a combination of things. I would, however, start by using the same premium fuel at the same gas station on a consistent basis, with Gumout All In One added for three consecutive tanks.
I personally use and recommend Shell V-Power, as I have consistently felt more power generated and superior fuel economy (+1-3 mpg) versus BP Ultimate and Mobil Super+.
Also, and this is going to sound funny, after you start the Disco in the morning, and before you put it in reverse, smell the exhaust. If you smell dense gasoline, it is a mixture that is very rich and may not be getting enough oxygen in the mix. If not, there may not be enough fuel getting into the engine, which would mean the mixture is too lean. That should help narrow down the cause if it stalls after that.
I hope this helps, but I would still advise taking the Disco to a LR specialist ASAP.

Thor - thanks for the input. I do run 93 all the time and most of the time get gas from the same few stations. I too use V-Power every 5,000 to 6,000 miles. Maybe I should try what you're saying in three consecutive tanks for a sure clean out. I'd say around a year and a half ago I replaced the MAFS, so I think it should be okay - but might be good to recheck. How can I check it to make sure, and do you think using a MAFS cleaner would be allright to try?

Run V-Power consistently, not just every 5-6k. The primary reason is that this gasoline has the best detergent capability of any gasoline out there (Shell fuel has powered every Ferrari since the first one rolled off the assembly line), and the V-Power available to us is 99% the same fuel as Ferrari racing fuel.:cool:
The secondary reason is that to get all the benefits you have to use it all the time. The nitrogen based detergent in V-Power may be the best available, but it is not super concentrated like a Gumout All In One. It is only with successive use and constant cleaning of the fuel system that all the gunk will get vaporized.
For example, I used V-Power for months, from the same gas station. But, for the last two tankfuls I switched to BP Amoco Ultimate and there was a significant loss of power and fuel economy. Since BP owns Castrol and I use only use GTX High Mileage (20W-50 in spring/summer, 10W-40 fall/winter), I figured to stay with the same brand. Oops. Back to Shell. It is a cumulative effect, is what it comes down to.
I am not familiar with what MAFS is, but I'll try to find out the answers if you let me know.

Thor - thanks for getting back to me. When I say I use V-Power every 5 - 6,000 miles, I mean the small gas treatment bottle. Seems like by your last posting you are saying fill up with Shell V-Power gas all the time?

MAFS is Mass Air Flow Sensor. I've heard good and bad things about using a MAFS cleaner to essentially spray clean the sensitive electirical parts and sensor. They make cleaners specifically for this. Of course, it's always a crap shoot.

I used to own a 1999 Disco II (one of the first accross the pond) and drove that thing to 189,000 miles. When I had it, of course BMW owned LR and techs said never to use gas treatments. When Ford bought LR, they began upselling gas treatments at the dealerships! So, who knows?

Yes, fill up with Shell V-Power gasoline consistently and ditch the V-Power additive in favor of Gumout All In One with every oil change (3k). Not only is it more concentrated, but is is good for up to 35 gallons. The V-Power additive is only good for 21 gallons, which is not enough since the Disco II has a 24.5 gallon tank. It also helps that Gumout is owned by SOPUS- Shell Oil Products United States.
Thanks for explaining the MAFS. As it is much different on the 4.6L than my 4.0L, I could not advise on how to maintain such an item, but I can say that I have never heard of spraying anything on it. The advice I always followed was replace it when it goes bad. I cannot imagine spraying an electronic device can be good. Shocking maybe, but not good.
The '99 DII I have just clicked 105K, and thankfully everything works just fine. I am convinced that the V-Power fuel and Gumout have a lot to do with that, but go to Wal-Mart for the additive as it is only $8.96 per bottle, and worth every penny.
Still, I recommend visiting a LR specialist ASAP. If it stalls while you are driving, well, that would be a very bad thing indeed.
Also, the LR techs advising against the DII you had were probably right, as the composition of fuels are different overseas. My understanding, and my memory from decades ago, is that the European fuels are much higher octane and thus more efficient. Here, the best we can get is 93 out East, 91 in the West. Our fuels, as good as they are, need all the help they can get.