revs drop and recover or die and car wont start for 30 mins

Ford Mondeo tddi 2003 - driving home at 70 ish for an hour then revs kept dropping, after a mile or so down to 5 mph, then as I gave up and got onhard
shoulder it picked up and went ok. Next day ok at 70 for 10 mins, hit traffic and revs dropped and recovered, then back to 70 and dropped again and finally died. Car would not start, fiddles with fuel pump relay and fuse, this took some 20 mins and then ok and got it 5 miles home. Sat with revs at 2,500 in garden and revs dropped on own to 1500 then recovered this repeats randomly sometime dropping to 500 rpm but throttle in same position. I did think I heard a quiet "clonk" a couple of times just before revs dropped.
any ideas as hrd to troubleshoot unless tottaly dead. Petrol was from shell on M23 and used 3/4 of tank with no issues.
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Is this car fuel injected or carbureted?
The first thing that popped in my head after hearing the symptoms is 'fuel starvation'. If the evaporative emissions system or the fuel tank venting system is messed up your car can develop a partial vacuum in the fuel tank from hard driving, and the fuel cuts off. Stop for a while, and air bleeds back into the tank slowly and it runs right again.
If it does it again, pull over and leave it running (if it will idle) and take the fuel cap loose. Be sure to look, listen and feel for either a partial vacuum (air whooshes in) or overpressure (air or fuel vapors out). And see if the engine suddenly starts running right.
An EFI car built to US Spec OBD-II would throw on the "Check Engine" light and set a trouble code if the evaporative emissions system is way out of whack. Not sure if Euro is the same, it most likely is.
Another possibility is the fuel pump or the fuel pressure regulator failing. Diagnosing that would take installing a fuel pressure gauge somewhere you can watch it while driving. I've seen people rig a mechanic's fuel pressure test gauge with a long hose, snake it under the cowl and tape the gauge to the top of the hood so you can see it while driving.
Rule for Ideas: If it sounds stupid but it works, it isn't stupid.
Safety Rule: Electric sender-style fuel pressure gauges in the passenger compartment only. You do not want a fuel hose coming into the cabin for a mechanical gauge, if or when the hose or gauge movement springs a leak you've got a huge problem...
--<< Bruce >>--
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wrote:

Its a TDDi??? and you put PETROL in it????
I'm suprised you got home at all.
Bruce.....I have never seen a carburetted diesel engine. 99.9% are fuel injection
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wrote:

Gee, 2500 RPM on a Diesel would be wound up pretty tight - even in car diesel engines they redline low, in the 5K region. Truck diesel engines are about to come apart at 3,500.

And ^THAT's^ what clinched it for me, I thought for sure that the guy is talking gasoline. Or Petrol for the Left-Pondians.

No shit, Sherlock! ;-)
EFI gasoline engines are moderate pressure port injection, diesels are pump-timed high pressure direct injection. Put gasoline in a diesel engine and the lack of fuel lubricity will kill the injection pump real fast, not to mention the detonation of the fuel is likely to put a hole through the crown of a few pistons even before the pump fails. No matter the failure mode, one constant is that it isn't going to be pretty...
When I think European spec cars, I'm expecting a lot higher percentage of diesel engines because it's taxed a lot less than petrol, you can afford to be a bit more leisurely in the acceleration department, and there aren't the pollution restrictions against particulates and pollution - well, until recently, anyway. So my usual question would be "Diesel, Carb, or EFI?" The sub-set question for diesels would be "Swirl Chamber or Direct Injection?"
But the OP was tossing the word petrol and other gasoline-centric terms around rather freely. And some "third world" areas stuck with carbureted engines a lot longer than the US and UK did, so asking "Carb or EFI?" is a reasonable question.
Now you have me curious... Grossly mistaken, or trolling?
--<< Bruce >>--
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Thanks Bruce,
No doubt you are not familiar with the Mondeo tddi, I should have listed the tddi out as "turbo duratek diesel injection". You dont get much evaporation with diesel ;-) like you do with petrol. It appears to be when engine is warmed up and when running over 2000 rpm. Will try removing fuel cap when symptom occurs and see if it is a venting issue, that is one that did not come to mind so thanks for that. My feeling is that fuel pump is to blame, at 182,000 miles it would be no supprise. But cant rule out a flakey sensor somewhere, but that would not cause car to slowly die and then not start start but go into "limp home mode" and flash upwarning lamp. One curious note is that the external temperature display recently just before issue started, sometimes shows as very low arctic like temperatures when we are having nice weather here. Not sure if a coincidence but I personally do not believe in coincidences, well no more than one or two in a lifetime in any case, so ECU could be issue but agin would expect warning lamp. What I was hoping was that someone with same or similar model had this issue and wasted loads of time trouleshooting and could same me some time. I need to force thye problem to occure so car wont start, then open fuel pipe at injectors, fuel distributor, and pump output to determine if fuel starvation is issue which I feel is the problem. If that ok then muxt be sensor or ECU in which case will have to pay the mighty FORD to plug it in to their mighty computer diasgnostics. But from my experience they only manage to tell you when something is so obvioulsy broken you know it and with intermittent issues like this they milk you for all they can because the staff are either too dumb so cant find problem or too smart so they can milk you. I am sure there are some good honest Ford garages out there but I aint found one yet.
Bruce L. Bergman wrote:

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Johneasty,
I think my partners car have the same problem as yours. Our car is a 1995 Probe, and we've done computer diagnostics and road tests in Ford Garage here in Leicester. As expected, computer could not detect anything and since they have experienced the sudden drop in rev while they are doing the road test, they suggested that it might be the distributor but that is without any assurance. Please if you are able to solve your problem, share what you have done so we can do the same. We also have heard that pressure like noise several times, and i am having a hint before that it is the fuel pump messing about. Thanks.
Ryan
johneasty wrote:

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