Engine mild surge (150 - 200 rpm) when engine cold

[Lord Sladacre]

Hi All,

 

I would appreciate the benefit - as always of your superior knowledge. I have noticed in the last week or so, that the engine will surge - almost like a wave (150 / 200 rpm) up and down until the engine is warm, then all is good. Any ideas what this may be would be very welcome please. I have heard some conjecture that it could be the clutch lining in the XF box going home, or a softward download required to the box.

Thoughts or identical issue / resolve would be great, many thanks for your time.

Regards

 

Dominic

[Lord Sladacre]

I'm beginning to think I imagined this. I think it was more to do with the road surface !! I have tried to monitor any difference or irregular "heartbeat" - pretty sure all is good. Age doesnt come alone......apparently. It had a full service in January and a new servo - which was prior affecting the changing of the gears due to the brake lights coming on. That was perfectly resolved, with a new servo.

[N6 JMX]

Hi Dominic, good that you think your imagination is playing a part in your issues, but keep an eye on it. It could be something as simple as a slight air leak on the inlet side, which seals up when the engine warms up. A smoke test might reveal a culprit, but remember to do it with a cold engine.

N6 JMX

[Lord Sladacre]

Hi Jim,

An excellent and likely diagnosis of the cause. I'm grateful to you. I am encouraged in that there are no messages on the on board computer which is not slow in coming foreward on just about every possible topic - except this one !! So if it is real, cannot be serious.

The car is running fantastically well, recently serviced plus gearbox with new sump pan etc., I usually achieve on a run of mixed roads 32 - 34 mpg, as shown on the onboard computer.

Thanks again Jim,

Kind regards

 

Dominic