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Matt, Mechanical Engineer
Category: UK Car
Satisfied Customers: 21854
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Thanks. I have just bought a mazda 3 diesel 1.6. on the way

Customer Question

Hi. thanks. I have just bought a mazda 3 diesel 1.6. on the way home it cut out 3 times when slowing down. Apart from that it runs like a dream. the journey was about 53 miles/ On the motorway not a problem, but on the way to the M25 in dartford it cut out twice, and once more getting off the m3 in Bagshot. If you drop the clutch and turn the ignition of and back on, it starts immediately no problem. Any ideas ?
Submitted: 2 years ago.
Category: UK Car
Expert:  Matt replied 2 years ago.


I'm assuming that you haven't got any check engine light on so I'd begin by looking for a lack of fue lpressure from the electrical pump at the tank.

If the connections to this are corroded or damaged then the pump could stop at any time or could not be running at full speed. Check that its relay switches in and out and the relay contacts are clean and bright – replace the relay if in any doubt and do the same for the fuse,
Ideally measure the pressure at the inlet to the main engine fuel pump and if this is low check the pump as described and also consider changing the fuel filter as if this partially blocked this too will reduce pressure.

If both of these are 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 brakecleaner, if it looks particularly clogged then replace it.

Expert:  Matt replied 2 years ago.
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