Why won't my Rangy pick up ?

Sounds like the timing is out, again. Now, if the dizzy body is clamped tight and the timing moves, it has to be due to mechanical wear unfortunately. I've only ever seen it the once, but if the timing chain is so badly stretched that it jumps a tooth, that will knock out both the camshaft and dizzy timing, making it run like an absolute pig, if at all. Garages blame ecu's (the fuel injection system's "brain") when they can't understand what is wrong, they blame the controlling item rather than isolate the cause. In your case, the ecu has NO control over the ignition or distributor timing on a 1991 3.9, it merely takes an input from the ignition coil so that it (the ecu) knows what speed the engine is running at, so as to work out the correct ammount of fuel to inject. I'd suggest they start by rechecking the ignition timing, thyen check for excessive slack in the timing chain by turning the engine clockwise by hand ensuring that the dizzy is turning with it, then backwards, noting how far it turns before the slack is taken up and the dizzy turns backwards with it. Any more than 5 degrees free movement at the crank and there is serious internal wear. BTW, it's always a good idea when posting on this NG with a problem to tell us where you are.... you never know what help may then be offered? Good luck. Badger.

At a wild guess from the antipodes I'd say Brentford, Middlesex.

Does it always misfire underload? Mine intermittantly misfired under load, mainly on initial pull away. Changed the usual leads, plug, coil, even the airflow meter from a friendly donor Range Rover. The actual culprit turned out to be the fuel pressure regulator located at the back of the engine behind the EFI chamber. It is a 15 mins job to swap if you have friendly Range Rover owner who is willing to lend it for testing. Otherwise i think they are £40-50 new.

Just my experience.

Martin

Thanks for all the info you gave me, needless to say, the garage now thinks the cam is buggered ! They are having to retard and increase the timing by up to 40 (yes fourty) degrees to get the damn thing running...which it does, but now really quickly ! I got the car back (unfixed) yesterday, so me & the other half are going to reset the whole thing get it to TDC then work on the basis that the timing chain is worn. Is there anything else I should be looking for ?

It's worth taking no. 1 spark plug out and using a small screwdriver or piece of stiff wire, find the true TDC position, I had a 3.9 in the workshop back in the summer that had running issues, apparently needing about 30 degrees static advance on the ignition just to run without backfirng, the std timing marks can be a considerable ammount out, but that was the excepttion rather than the rule. Might be worth checking though.... Badger.