Possible First Problem with LC500

[malcolmw]

My LC500 has suddenly started to do about 3mpg less than usual and is making the V8 growl at all revs instead of the exhaust valves opening at over about 4K. I think the valves are stuck open and the resulting lower back pressure is what is causing the mpg loss.

I am going to contact my dealer tomorrow for them to have a quick look. It's hardly a serious issue but something has changed at about 4700 miles up.

Has anyone else experienced this?

[Herbie]

Don't forget that mpg always drops in colder weather.

[malcolmw]

More true with hybrids than conventional ICEs, I think but this was like a switch being turned rather than a slow process as the weather cooled. Back in March my mpg was still pretty good in the cold.

[malcolmw]

Well, Lexus Hedge End did have a quick look but requested to have the car for a few days to diagnose the problem properly. It was due to go in on Tuesday but I will be contacting them tomorrow to cancel the appointment as the problem seems to have gone away. I thought the car was back to normal on Thursday but I wasn't certain that it just wasn't me getting used to the changed sound.

I took my partner out for a trip to Lymington today and she is also convinced that the low rev growl is gone and silence has returned when cruising. I also noticed that the exhaust "crackle" is back if you give it a boot in Sport mode and the sound now picks up at about 4000 rpm like it did before.

Now, I have realised that the changes to the car have coincided with a refuelling both times. Is this coincidence or causation? I filled up just before I noticed the noisier exhaust and refuelled again last Wednesday. Since this refill, my MPG has gone back to 25+. Could a fuel problem really have caused this or have the valves just become unstuck? 

 

[rayaans]

26 minutes ago, malcolmw said:

Well, Lexus Hedge End did have a quick look but requested to have the car for a few days to diagnose the problem properly. It was due to go in on Tuesday but I will be contacting them tomorrow to cancel the appointment as the problem seems to have gone away. I thought the car was back to normal on Thursday but I wasn't certain that it just wasn't me getting used to the changed sound.

I took my partner out for a trip to Lymington today and she is also convinced that the low rev growl is gone and silence has returned when cruising. I also noticed that the exhaust "crackle" is back if you give it a boot in Sport mode and the sound now picks up at about 4000 rpm like it did before.

Now, I have realised that the changes to the car have coincided with a refuelling both times. Is this coincidence or causation? I filled up just before I noticed the noisier exhaust and refuelled again last Wednesday. Since this refill, my MPG has gone back to 25+. Could a fuel problem really have caused this or have the valves just become unstuck? 

 

Where did you fill up? I know that Tesco had some contaminated fuel recently.

Fuel problem could have caused the issue yes. 

[malcolmw]

Not Tesco. The same local BP  garage with Ultimate Unleaded 97 each time (supposedly!) I will ask Lexus what they think.