Dear all,

I have written about the P0400 code I was getting and although a new EGR Valve was installed last December, the CEL came up during my first drive and my local Jaguar Dealer/Workshop said they need to replace the EGR Valve (again!).
I told them - specifically - about other possible causes for this, but they were adamant that the EGR Valve was the culprit.
So they changed it (without cost for me - so I was fine with it)..again.

And today, AGAIN.. the horrible, horrible orange Engine symbol popped up once more (anyone else really dreads this light as much as me?) and when I checked with my OSD2 app: P0400 "EGR "A" Flow"

So I was tracking my Fuel Trims today and although I tried to read up on all the information available on this great forum I still canīt figure out if my records show something extraordinary, faulty, worrisome, or if the readings are fine?
I attach two of those readings (in one excel file; two tabs) and appreciate ANY comments/feedback on them.

What I did notice is something else. Whenever this code is popping up, I can hear a rather irritating and high-pitched whine whenever the RPM drops below 1K.
It does not happen, when I rev the engine above 1K, but you can hear it in idle and sometimes even shortly after I have switched the engine off.
I recorded this sound with my phone and have attached the sound clip as well.

Please remember Iīm more of a "Top Gear Engineer - ambitious, but rubbish", but to me, that suggests an air leak. Something sucks in air and produces this whistle.
But hey! Thatīs why Iīm posting this: any pointers or even "how to fix this" recommendations are hugely appreciated.

Most pressingly: I plan to go on a two day trip with this car starting tomorrow - any dangers involved? :/

Thank you all,
Berglmir

 

I'm not an Excel or Windows guy but unless the trims are as posted so many many times you've a problem. If the noise might be air sucked in you've a HUGE problem as normal leaks can't be heard.

Any shop that can't cope with something so incredibly basic for OBD given it's 20 years old ought to be sued and shut down.

 

I'm still learning about this, but the LTFT figures for both banks between 18 & 19.5 for most of the time are high and suggest there's a problem:- is the motor at idle when they are at this level?

 

No. This was tracked on a 35 miles trip - to and fro.
Average Speed most of the times, going up to about 100 m/h once.

Thanks for your feedback.

 

If the fuel trims are that high at idle and drop down to ten or less I would look for a large air leak. The accordion section of the intake tube is a good place to start. But if they stay high at 2500 rpm it could be the mass air flow sensor.

 

If it is hissing on shutdown with the throttle plate closed, look downstream of that point.

 

Try following the often-posted ways.

 

If you have an EGR code, double check the accordion steel pipe between the exhaust manifold and the EGR valve (this is how the valve gets exhaust gas). It is known to develop leaks/cracks. It is in the general area behind/below the throttle body. These cracks also contribute to air leaks and high fuel trims.

Remember, Fuel Trims are a function of rpm and engine load. So, visually, it is more of a "surface" or elevation map, with rpm and Load as coordinates. This is certainly not a single number that gets averaged out over the duration of a trip. The only "averaging" is that, for a given rpm and Load, the Long Term trim gets updated by the average Short Term trim at that same rpm and Load every few minutes (2 minutes, if memory serves).

As already pointed out, start with idle Long Term trims, and bring them down to below 5 by plugging every air leak. As you plug leaks, these trims should come down, starting with negative short term trims.

 

Thanks for your input Fmertz - I think this is spot on.
The whining sound comes exactly from where you have indicated: behind/below the throttle body.
My - proper - workshop took a look at it today and tested it with a spray - there was a definite drop in rpm, when sprayed in that region.

We also test-drove the car today (quite hard) and the P0400 never showed itīs ugly head.
I also tried to reproduce the MIL by following the described test procedure i.e.
"Engine at normal operating temperature;normal varied driving for 3 minutes; 37 –75 mph (60 – 120 km/h); 1300 – 2500rpm; then decelerate at fuel cut-off (foot off accelerator pedal)
Surface elevation < 8,000 ft (2,438 m)" - no "success".

Iīll check and update you all, when
a) the whine has stopped and
b) the Fuel Trim levels have normalized and
c) if my P0400 friend has visited me again after a) & b)

Thanks again,
Berglmir

 

Just got back from a family vacation and can get back to those niggles.
Before I do yet another question:
When you stop the car (red light; idle) what does your "current mpg" screen say?
Mine goes up to 9 mpg (99.9 l/100km)

I drove mostly in town and averaged 10 mpg - I donīt mind bad economy, if itīs MEANT to be that way.

Thanks for your feedback guys (and ladies).

 

At rest the "instant MPG" should be zero and the "average MPG" is whatever you are averaging. If you are just driving around town 10mpg sounds low, but it depends on how you are driving the car.