In my hunt for a possible vacuum leak I am focusing now on the gas tank cap. I did notice that although it seems to turn and close, I don’t hear or feel any kind of clicking sound. Should there be a kind of locking sound as it’s pressurized? The engine light is on but only showing the lean codes. FYI, the car runs very well with a steady idle and no hesitation.

 

I can only report that on my car there is no locking click, and the car is free of trouble codes.

what exactly are the fault codes showing. The intake accordion is a usual suspect.

Z

 

[QUOTE=zray;[url=tel:2317284]2317284]I can only report that on my car there is no locking click, and the car is free of trouble codes.

what exactly are the fault codes showing. The intake accordion is a usual suspect.


The codes are lean codes on both banks with long term trims around 19 both sides. I can’t find any air leaks so I’m beginning to suspect either a bad fuel cap or some fuel delivery problems such as a fuel pump going south

 

The gas cap does not click on our cars.

If the seal on the gas cap is bad you should see some codes for evap checks failing and there will be a message in the dash for "check gas cap". If you have never seen this then most likely the cap is not the problem.

You don't mention which specific model and year you have, which can help with diagnosis.

But since you see the same trims on both banks, odds are you should be looking somewhere between the throttle body and the MAF. Have you tried spraying MAF cleaner here and there while the car was idling? This will usually cause the car to stumble and the trims to go crazy when you hit the leaky spot.

 

A faulty cap will yield an EVAP leak, not a LEAN fault.

 

Thanks for the input. Too bad it's probably not the fuel tank cap; that would have been an easy fix. I'll try some spraying around the area that was suggested.

 

As I mentioned earlier I have been hunting around for a possible vacuum leak and upon feeling around underneath the concertina part of the air intake duct on my 2004 XKR I found some kind of plastic extension which is brittle and obviously damaged by heat. It’s impossible to see from above, but I can feel it crumbling! I guess it’s part of the air intake duct. Does anyone have photos of the intake pipe showing the underside area below the concertina section? What’s the purpose of this kind of small tubular extension part?
Thanks in advance