Problem with intermittent stalling at low or high speeds – 1998 Disco
 

I recently purchased a 1998 3.9 L Disco I and I’m having an intermittent technical problem that I can’t figure out. I also live in a very remote country so I have no access to computer diagnostics and getting replacement parts is slow and expensive. So I’d like to get the best diagnostic possible before I try and import new sensors or whatever else may be wrong. Symptoms:

- The engine will stall about 20% of the time I’m stopped at a red light. After which it restarts and drives without issue.
- Between 70 and 80 kph a loud humming noise begins – mostly just noise, very few vibrations. If I slow down below 70 it goes away, but if I maintain or increase speed, the noise gets louder and then the engine starts to lose power and eventually dies. In these cases the engine will not immediately restart but does restart after 30-60 seconds and then can be driven again.
- At other times during normal driving between 60 and 70 kph, the service light will occasionally flash for a second but it does so rarely and never stays on. The light usually flashes at the same time as the engine sputters or jerks as though no fuel is being delivered to the engine. As long as I am not above 70 this is usually a one time sputter and then the engine recovers with little loss of speed.

Any thoughts will be appreciated. From what I’ve been reading on the forum it could be crank shaft or oxygen sensors, but I’d like to get the best possible diagnosis since I’ll have to import any parts that may need to be repaired.

You need to not guess, find or buy a scanner so you can actually find the problem.
As for the stalling, clean your t/body and IAC.
When was it last tuned along with new wires?

yep, I missed that. The IACV cleaning could well help idle, and any old small vac hoses shold be carefully checked for cracks and leaks.

Thanks for the suggestions. Unfortunately it is difficult to find a scanner in this country so I'll try cleaning the throttle body and IAC and see if that helps. If I can manage to find a scanner or import one, I'll update with the code. As for tuning - it was last done about 6 months ago but that was before the car was used in a 5,000km international rally...

Your truck does NOT have a crank position sensor!!!!!!
You have the 3.9, which has a dizzy, you probably do not have O2 sensors either, but check anyway, just crawl under the truck and look for them on the exhaust.
Let us know if you do or do not have them.
No idling would lean towards a dirty throttle body and idle air control valve and port, clean them all.
A easy test of that is to hold your foot on the gas pedal, keep the RPM around 1000, does it run fine? If yes then it is a idle air control issue.
Also make sure the air filter is clean and the MAF sensor is secure and plugged in.
The high speed cut out/stutter would either be a weak fuel pump, failing fuel pressure regulator or a failing throttle position sensor or failing ignition amp module.
A scanner will do you zero good as our truck is not OBDII compliant.
Look under the passenger seat, there should be a black box with a LED display on it, that is your code reader, with the ignition on (but not running) that box should show a 2 digit number, that will be the fault code number, Google that fault code(s).
These trucks are designed and programmed to run on the poorest quality of fuel but if the water content is to high it will cause run problems.
If you can add a bottle of fuel injector cleaner, if you cant get that or any type of fuel line antifreeze or the like then add 1 small bottle of rubbing alcohol to a full tank of petrol and then do not add more fuel until the low fuel light comes on.
Water sticks to alcohol, this will allow it to be burned in the engine with the fuel slowly instead of sucking up "drinks" of water and no fuel, like when turning a corner or stopping.
Here in the US we have ethanol (alcohol) in our fuel from the petrol station so we dont have that problem.
Your truck is ROW (Rest Of the World), ours are NAS (North American Spec), two totally different trucks that are not so different.
What country are you in?

I'm becoming deeply suspicious that I have water in my fuel causing an intermittent problem depending on whether it settles or if the fuel pickup gets fuel or some water. I seem to have trouble most when the tank is settled and once it gets sloshed around a bit the car runs better.

I tried siphoning the tank but was unsuccessful in getting a tube in the tank. I suspect it has some kind of baffle to prevent siphoning. Anyone know?

I drained it down (took out about 15 gallons) to low fuel level using the schrader valve on the fuel rail. I have a screw-on adapter for schrader valves (from a can of Fix-a-flat) and ran that out a vinyl tube to some Jaz jugs on the ground. Then I refilled with new fuel. The problem is I'm afraid the water is down at the bottom of the tank where I didn't drain. How can I get it out? I wish it had a petcock or something easy.

I put in a bottle of isopropyl alcohol gas anti-freeze/water remover (Napa equivalent of HEET brand). But I'm concerned that there's more water than that will help with. I suppose maybe it will take a few tanks with the alcohol in there. I know the ethanol's already in the gasoline but that can come pre-saturated so it's not always the solution by itself.

If you remove the fuel pump you can drain the tank completely.
Roll up the carpet in the cargo area, open the access hatch, remove fuel pump, siphon tank.
You cant get it all, but you can get most.
Then add the gas line antifreeze and 5gal of fresh gas.
Then drive it until it runs out of gas, of course carry gas with you.
I would repeat that 2-3 times and then fill the tank and add a bottle of injector cleaner and just drive it normal after that.

YOU GUYS ARE GENIUS .. #thatisall..

Thanks Spike, this is very helpful. I'll take a look for the code box tonight and post an update (you're right about not being OBDII compliant). I'm located in Tajikistan - it's not the most landlocked place on the globe, but it's close.

I'll take a look at the t/body and IACV this weekend and also check on O sensors. My build is UK version so there is no LED fault box that I can find and if it's also not OBDII compliant then I don't know if there is a way to get fault codes outside of buying a very expensive LR diagnostic tool. There are definitely no garages with this in Tajikistan...