The revcounter is driven off the coil so it sounds like there's a bad connection in the low tension side of the electrical system. Hard to find until it breaks for good though. All you can do is go over all the connections and clean and check them. It could be anywhere from the ignition switch onwards. If it happens regularly you could wire the coil direct to the battery and see if the problem stops.
I had a Ford Falcon when I lived in Australia that did this. The engine was a 3.9i "Multipoint" - i.e. a straight six with fuel injection on each cylinder (as opposed to CFi)
You could drive for anything from 20 minutes up to about 3 hours before the engine would pack in. Rev counter would plummet to zero, although the revs dropped down slowly, relative to road speed, as you sidled towards the kerb!!
The culprit was the ignition module - basically a small piece of electronics next to the distributor, which (I think) was responsible for generating the timing / frequency of the spark.
The Falcon was a 1998 machine - could it be that the big XR4 Sierra engine used the same technology? Worth a thought, anyway.
FWIW, the replacement Ignition Module cost me $80 Aussie dollars. That's about 30 in GBP.
Hope this helps (probably not!!)
Al
Hi, I've a 1991 (H) Sierra XR4x4 (2.9) & ever since ive had it the engine, for no apparent reason, just cuts out all of a sudden, it 'usually' starts again straight away. I posted a similar message to this about 3 months ago & was advised to change the fuel filter which I've done but the problem still persists. I usually get a warning of a backfire or 2 prior to cutting out & the rev counter just dies even though the revs havent????
Because the problem only happens every now & then the garages I've taken it to have failed to find the problem - but still charge!! Does anyone have an idea what might be causing this as I'm at my wits-end trying to sort this out.
'Frustrated' Dave
A lot of Fords around that time had problems with the pick-up coils and the module in the distributor. Might be worth trying if you could get one from a breakers.
John
In news:u%FVc.290$ snipped-for-privacy@newsfe2-gui.ntli.net, Dave decided to enlighten our sheltered souls with a rant as follows
Heh, I can cure this for you.. I've got a 2.9 XR4x4 with a tired engine in it, but it starts every time. Yours for £300.. Taxed and tested an all. Bits are worth more than that...
We used to have one of those years ago [H482 TKW], was a great car, used to eat ECU's until ford did some sort of mod.....
Tom
Hi Guys, Thanks for all your advice, I'm now going to be concentrating on the distributer, coil & connections to try & solve this - thanks again for your help.
Not so 'Frustrated' Dave
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