Doctor Diesel


Dear Doc,

Hope you are keeping well.

When the Ford Fiesta was having its fifth service at my local Ford dealer a couple of months ago, they told me that there was an update to be done to the car’s brain and that this would be carried out free of charge.

The car is running fine and returning 60mpg+, but since the upgrade, there is a slight hesitation from the engine driving in fourth or fifth gear between 1,500 to 2,000rpm. It only happens occasionally, and no warning lights are showing.

Do you think that this would have anything to do with the upgrade or possibly something else starting to go wrong? I haven’t asked the garage about it yet as I would value your opinion first.

Thanks for your help.


Hello Kenny,

Thanks for your email. You haven’t mentioned which engine powers your Ford Fiesta, but given the reference to 60mpg, I’m assuming it’s the 1.6-litre TDCi unit, but possibly the newer 1.5 TDCi powerplant. I’ve always believed that it’s possible to achieve truly impressive economy out of a Fiesta diesel – your email just proves it. What a shame the media hype has led to the downfall of small diesel cars. It’s a huge step backwards if you ask me.

It’s interesting that you’ve noted a hesitation after the software update. I know of owners with Fiesta diesels who felt like their cars were transformed following an update, with any hint of a flat spot removed from the equation. The first thing I would suggest is to take it back to the dealer. If it has come back to you feeling worse than when it went in, it’s their duty to sort it for you. Don’t let them fob you off – it needs to be looked at. It sounds like it’s struggling under load in a high gear. There are a number of possibilities, including EGR valve, an air leak or a damaged fuel pipe. Get the dealer to plug it in for a diagnostic check, but don’t let them charge you for the privilege. Also, make sure you ask for a detailed list of what was checked and changed as part of the service.

Good luck and keep me posted.


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