Last summer our 3.9 Discovery broke down several times. It started again after about 5 mins and never did find the problem. Yesterday it did it again several times. The engine was cold as I had only done about 2 miles. Each time I eased off the throttle the revs would just die. If I kept the revs up when stopped it was ok. Anyone got any ideas before I start changing things for the sake of it? Thanks Richard
Um...sounds a bit like the old "dodgy spider" syndrome (crap soldering in the the PCB). When it does die, will it not restart for a period - if so, you can jury rig the coil to the battery to bypass the immobiliser - if it starts - that's the problem. ISTR that Rogers of Bedford have a nice fix for this - that doesn;t involve buying the new stupid LR fob replacement at £300..!
Neil, I did wonder about the 'dodgy spider thingy' but then I thought why would it keep going if I managed to keep the revs up? BTW it does the same on LPG and petrol so I'm assuming its more of an electrical problem rather than fuel. Richard
Mine was intermittant - the local LR garage blamed all sorts of electrical things....but it was the spider - it;s the heart of thebeast ;-) Only has to rattle a bit. Even the AA diagnosed a faulty inlet manifold gasket?!?!?!?!
I'd take a look at the air flow meter, between the air intake and the engine. This isn't because I know one end of a V8 from the other, but rather that I had a similar problem on my 4.6 and that's what it was. If you can find a friend to swap with, you'll soon find out.
Of course, now somebody's going to point out that the 3.9 doesn't *have* an air flow meter and I'll look a complete berk.
If it does it on LPG as well then you can more or less rule out the complete EFi system including the air flow meter and ECU.
Normally the only common components are the throttle position sensor ( throttle pot) and (possibly) the idle air control stepper motor. The TPS could cause your problem if it was giving out erroneous readings in the lower area - possibly causing the engine to over or under fuel and make it difficult to start but I'd expect the ECU to work around that.
The ignition system would be my main suspect as it is independant of both fuel systems and is capable of causing the problems you describe. A good starting point would be plugs and leads. Plugs take a hammering on LPG and it's a good idea to replace them every 12000 miles (I know some people replace them every 6000). HT leads need to be in good condition, especially for LPG. After that you are looking at possible distributor cap/rotor arm problems, a faulty ignition amplifier or a worn distributor. It's unlikely to be the coil if it runs OK at higher revs.
It is possible that the infamous spider could be the cause but IME this tends to stop the engine dead at any speed rather than be rpm specific. Easiest way to rule that out is to supply the ignition with it's own feed.
Neil, Pretty please I could do with borrowing these, I have a Disco V8 efi that is dead in Normandy, and I'm going out this weekend to try to get it going. I'm in Bedford.
Not nececelery. Mine had an intermittent fault, so it would check out fine most of the time. Only sussed it when it *happened* to play up just as I pulled out of the workshop at James French. 5 minutes earlier it'd been working flawlessly.
Which is why I thought swapping with a mate'd be a good idea - if his started playing up and Richard's didn't, it would be a bit of a clue.
Its definately an intermittant fault. It happened last summer and had been fine until yesterday. Drove into town and it would stop everytime for about
6 miles. After getting back in after shopping it was fine all the way home. If it did it all the time I would get it checked but I dont fancy paying £xxx amount for them to say they cant find anything wrong.
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