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Matt, Mechanical Engineer
Category: Ford
Satisfied Customers: 22727
Experience:  BEng hons Mech engineering, in auto industry 22 years
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We have a cmax which losses power every so often when in

Customer Question

Hi we have a cmax which losses power every so often when in the outside lane of th motorway! the rev counter just slowly drifts down. nothing on diagnostics in the garage and no ideas. can u help
Submitted: 2 years ago.
Category: Ford
Expert:  Matt replied 2 years ago.
hican you tell me what engine size and fuel type this is please?also when was it last serviced?
Customer: replied 2 years ago.
hi 2l turbo diesel, regular ford servicing by main dealer, the last one c 4mths ago, we also had the additive for the DPF topped up recently. The problem started about 3 years ago a few months after we got it but very short (under 10 secs) and very occasional, always on long motorway runs. Last long trip it twice lost revs on consecutive days and for as long as it took me to get to the hard shoulder. Once there, engine still running, it behaves fine and u can just drive off again.
Expert:  Matt replied 2 years ago.
Hello 1st consider changing the fuel filter as if this partially blocked this will reduce pressure at the main pump If OK then also check the connections to the EGR valve, if either the vacuum pipe of electrical connection are damaged / corroded then the EGR can be on all time which certainly will hurt performance.Its also possible that its a fault with the EGR valve so its worth removing the valve and cleaning it out with brake cleaner, if it looks particularly clogged then replace it. If this is OK then check the small vacuum lines to the turbo and its connected control solenoid on the bulkhead, any cracks or leaks can give turbo issues and its best to have the boost pressure measured to check that the turbo is healthy If its a variable vane turbo( they'll be an actuator on the turbo body - but not a wastegate) then check its vacum pipework as above and check the connections to the diaphram / solenoid valve Also worth checking that the glow-plug relay is switching off as they can stick on and leave the glow plugs also on - on some cars this can force it into limp home Also worth considering a bottle of injector cleaner into the tank as a clogged injector nozzle will reduce power and give poor combustion - the next stage on from this is to remove all the injectors and have them ultrasonically cleaned and flow checked
Customer: replied 2 years ago.
hi, would these problems not show up on the diagnostics the garage run?
Expert:  Matt replied 2 years ago.
Hello to be honest you might get a hint from an diagnostic but there's no direct fault code for any of the faults I've listed ( with the exception of the EGR) a blocked fuel filter may show up as low fuel pressure for example but if the pump is starved of fuel it can just stop with no chance to register low pressure 1st as there's no fuel to make it run
Customer: replied 2 years ago.
not the fuel filter, had all the obvious checked, and presumably not the EGR as there is no error code, so start fault finding with yr para 3??
Expert:  Matt replied 2 years ago.
hello that would be sensible, I'd also check the state of the ECU power fuses and relay for any sign of overheating and cracks
Customer: replied 2 years ago.
OK we'll have a go
Expert:  Matt replied 2 years ago.
good luck and get back to me on this post