I have found a used VSS unit and installed. WE will see how it goes. In the meantime , many thanks. Regards Tony G

 

After replacing the VSS and running the truck a few days, it is back to the original fault. There is nothing out of ordinary in starting or normal driving. An hour into a run today, travelling ~ 65 kph the spasmodic stalling happened again. On increasing the throttle it cleared itself. It is difficult to describe the condition, I originally mentioned fibrillation, but if you can image draining out a sink filled with water, then intermittently stopping the flow with a plug, there is a shuddered jerk. THe LED I have attached to the low volt coil is not affected. T appreciate any further advise. Regards Tony G

 

Wonder if you have exhaust valves carbon sticking? Apparently the older style valve stem profiles don’t self clean around the guide well enough and can stick at traveling speed. Sure sounds similar.

 

Hello again. I'm still experiencing the rhythmic fibrillation issue with my Discovery I. I acknowledge the strange wording explanation, but it examples the fault condition. On running at normally running temperature, at speeds 40 to 80kph the engine will start to spasm. If you can imagine the effect of a flutter value flicking in and out of an air throat. I replaced the MAF (second hand) and getting a reading of 1.8volts on the terminals. Also, the idle steeper valve (new) has been replaced. rubber pipes have been replaced and the penlum chamber refitted with sealant. As mentioned prior the ignition coil and amplifier have been renewed.
A previous reply mentioned a sticky exhaust valve. Other advise on this mentioned this fault would not give the jerky cut off effect of "stall-go,stall-go,stall-go,etc".
A question, would a diagnostic meter record historical faults? Is it worth having a shop run a test sequence on the Discovery I systems?
Could it be the fuel ejection?
Appreciate your comments, Many thanks, Tony G. NZ

 

have you examined the distributor cap and rotor ? dirty. burnt, corroded terminals inside can really mess up the firing and lead to intermittent problems

 

Many thanks for your reply. The distributor cap and rotor is very clean, with no cracks. Replaced HT leads n plugs, also the wiring from coil, via amplifier is solid. The wiring to inside distributor has been metered for movement faults, all appears OK. The distributor springs are firm and rebound OK. Vacuum tube replaced and fitted firmly. Excellent HT blue spark. The engine normally purrs, but with a slight tappet noise. Again thanks, RgdsTony.

 

It's hard to figure out the behavior from your description. And since it's intermittent, you've really got a tough one on your hands.
Just taking a couple stabs at it (based on the other thread), here's where I'd look closely.

vacuum leaks. I think you mentioned you replaced a pipe up above. It looks like there are several. Did you replace them all? Are you sure they're in great shape, and everything else they're connected to is too? Can you suck the vac line on the distributer and hold pressure with your tongue on the end of the tube? Is the advance function on the distributor in good shape? See especially post 5 on this thread: https://landroverforums.com/forum/di...-layout-44078/

Fuel pump. You've been throwing a lot of parts at this and I'm not saying you should do this too, but do you know that yours is solid? I think I've run across threads relating to this before, but haven't needed to pay much attention.

Fuel pump relay. According to this thread: https://landroverforums.com/forum/di...cement-101465/ similar symptoms are pointing to the relay but it's not concluded. Might be worth following up with @disco96sd and seeing if that solved his issue. If it's a relay that's used in 2 different places you may want to swap them to see if it changes behavior.

Sometimes small problems become bigger problems and get easier to troubleshoot. If it's manageable with your workarounds, maybe you can live with it until it gets worse and is more easily reproducible? Not ideal obviously....

 

Hello CantComplain. Thanks for your suggestion. I have considered your advise on the relays. Not the fuel pump relay as I'm reading a constant 38psi at the fuel rail. I mentioned previously on the refurbishing the fuel injectors and your comments bought me back to the electrics of these. Basically there is a change in the characteristics of the fault in that it is more regular in the cut out/cut in. The fault appears after driving the truck for sometime before kicking in. It crossed my mind that there could be a higher temperature involvement which led me to looking at the fan control relay schematic. I attach a jpeg of the schematic which shows the fan regulator (unit 11) is on the same circuit as the Engine Control Load injector relay (Unit 5). I have arrowed the line. The question then is, could the fan relay (temperature related) be interfering which the injector circuit? I inserted a 12v LED inline on the Brown/Orange wire (marked X) that connects into the current line to the injectors with the anticipation that a glowing LED may fluctuate on the condition of the fault. However, bugger me on starting the engine the LED fails to illuminate. (the LED checked OK before installing). How can this be? Does it mean current only flows when the ECU switches on the fan relay. Should I have installed the LED off Pin 87 (Brown/Orange) of the Engine Control Load Relay. I'm at a loss to make sense of the circuit.
I appreciate your comments and cordially invite others for advise.
On the question of a stick valve, I have added 125mls of Marine 2 Stroke oil to a tank of petrol to see if that will lubricate up into the valve shafts.
Many thanks. Regards Tony G.
ps. Note the schematic identifies two unit 5, I think this is a print error as one appears to be a fuse box.

 

Still having the same issue after all this time, eh?
I'll take a stab at it.
What is the difference in the rpm range from normal to the flutter, road speed, auto or manual transmission?

 

Hello hrhoward. The most resent occurrence happened on the motorway travelling at 105k, at around ~2100rpm. The motor was running at normal temperature on the gauge, outside air temperature ~20 degree C. The D! is an automatic. Thanks for your reply, I could just replace the relays, but I have replaced so many sensors and still haven't solved the problem. Regards Tony