Rough start when hot

[DOROTHY]

Hi, I have a 2006 non supercharged X150 convertible with 46000 miles. Had her about two years now and apart from normal service bits she has been no trouble. Last big trip was to Sorrento in Italy which was fabulous. The problem I have appeared in the very hot weather we have just had. After the car was hot, if left for 15 to 20 minutes, on start up, she would be rough for about 3 to 4 seconds, or would stall. After that she was fine. I changed the plugs, just in case, but no difference. This does not happen every time. My friend, who has an identical car, had the same problem. His specialist changed two small vacuum pipes in the engine, I would like to do the same, but I can't find where they are. His report says that the codes shown on his car were PO171-00 and PO174-00. Can you please tell me where the pipes are. I would normally take the XK to my specialist, but frankly, after my last service, I have lost confidence in them. Thanks. Rob.

[mike020150]

Practically any vacuum pipe can split, leak or become disconnected causing the fault codes you've recorded for your car. Try checking around the throttle body for likely culprits. Mike.

[J44EAG]

A defective or semi defective cylinder head temp sensor can also cause difficult starting.

Some Forum Co-ordinators witnessed the sensor failure on my V8 S-type some years ago at Weston Park. Located near the water pump and thermostat, it is a screw in sensor which is quickly changed. Ensure you get a genuine OE unit not after-market.

This sensor is particularly prone to failure after 80k miles of use. A full hot dash gauge reading often occurs when the sensor finally fails. It links directly to the power train ECU and can mess up fuelling as well as hot and cold starting.

Mike K

[andypryce]

Rob,

I have a cylinder Head temp sensor that I bought for my now departed X150, if you want it send me a private message with your address and I will post.

[DOROTHY]

Hello,
Thank you everyone for your advice. I checked the XK today, and the only code showing is P0000. Thanks Mike, I will check all the hoses I can find around the throttle body. Andy, I sent you a private email, which I hope you received. I am not too good on the computer. Perhaps you could let me know via this site if you did not get it.
Thanks again
Rob

[andypryce]

Hi Rob, yes got your message, sensor posted today, hope it helps, of no use to me as car now gone and replaced with convertible XK8. Never quite got round to fitting it.....

[DOROTHY]

Thanks Andy,
Very grateful to you.
Rob

[steve_m]

I'm new to the V8; is that the coolant temperature sensor or some other type?
Also, does anyone have a part number handy?
Thanks.

[mike020150]

hi Steve,

If you pm me with your car's VIN, I will be able to give you the correct part number. Mike.

[steve_m]

Thanks Mike.
I'm away at sea at the moment so I'll do it next week.