Hello - working on a 2006 Jaguar XJ8L with the 4.2L NA engine with a P0171/P0174 codes. I have smoke tested for vacuum leaks and corrected all but one. I am getting smoke coming from the body of the EGR valve with key in both on and off positions to try and rule out it needing power to close.

I reattached the intake and idled the engine. STFTs are affected when spraying brake clean at the EGR valve in a big way. At idle the trim info is:

LTFT at idle - B1 = 20 B2 = 18
STFT at idle - varies from -3 to +3

Increasing to 2500rpm shows a decrease to LTFT to B1 = 10 B2 = 8, which would indicate a vacuum leak present.

When spraying brake clean at the EGR body, STFT will lower to B1 = (-28) and B2 = (-25).

That leads me to believe the EGR valve needs to be replaced, but during my research on this forum and others I see posts referencing that smoke from the EGR body during a smoke test is normal. Any advice or experience with the same issue would be appreciated! Am I correct in thinking the EGR shouldnt be letting air/brake clean in during operation at idle? Thanks!

 

Believe i read they can be often be cleaned & will work again.

 

The EGR valve should use a DC motor that drives the pintle open/closed as needed. Once it's in the closed position it would stay there. These EGR valves also have a position sensor so that the ECM can detect a stuck valve. You can view the data PID in an OBDII tool.

I don't have a good answer for you on how much leakage is acceptable here. I assume it is like the throttle shaft bushing that wears with time and starts leaking, it may very well be too worn to seal correctly. External leakage on the EGR would certainly be an issue. Hoping someone else has more detailed feedback, I'm interested to know how this turns out.

 

Hi Chris,

Welcome to the Jaguar Forums! It's great to have you with us.

Are you sure you are looking at the EGR valve and not the Crankcase Vent Valve? The EGR valve is tucked behind the right-hand cylinder head (as viewed from the driver's seat) near the firewall and looks like Part 1 in this diagram:




The Crankcase Vent Valve (CVV) is often mistaken for an EGR valve. It is the black plastic disc-shaped device at the front end of the right bank camshaft cover, Part 2 in this diagram:



It is very common for the CVV to leak from the two rubber O-rings on its short pipe that fits down into the camshaft cover, and for the Crankcase Breather Pipe, Part 1 in the diagram, to leak from its O-rings inside the quick-connect Norma fittings. It is possible that the CCV has split along the ultrasonically-welded seam in its disc-shaped body.

Leaks at the EGR valve are less common but are possible. The gaskets for the valve are thin springsteel sheetmetal, and the sealing ridges in the gaskets compress and flatten over time. The EGR valve has a four-coil stepper motor inside that can open or close to any position commanded by the ECM.

Cheers,

Don

 

Did a smoke test on my '06 intake this evening. I found that my EGR is leaking massively as well. This is definitely from around the pintle where it goes into the cast iron section of the EGR. Will start looking for a replacement and see if this is any kind of known issue. FWIW, I do not have any lean codes, total fuel trims around 7% for both banks, but I have been chasing issues with the engine idling poorly... intuitively felt like it was a vacuum leak, and this would definitely be contributing to that. Found 2 other leaks with the plenum and PCV which are somewhat typical.

 

Initial STFT after cleaning was showing at -25% indicating a correction to the issue, but after warming up, and I'm assuming, drying out from the ultrasonic bath, it has started to indicate a leak there again. I'm back to the same symptoms before the cleaning with LTFTs in the 10-15% range now. So an overall improvement, but STFT are still affected when spraying brake cleaner in the area that mhamilton's post is indicating with the red arrow. Mine is not coming from either of the gasket mating surfaces, but the main body itself.

I am positive it is the EGR valve that I am referring to, as indicated by number 1 in Don B's first diagram. Although it is located on the passenger side of the throttle body at the front of the engine on this vehicle and not against the firewall.

 

Sorry Chris,

In my mind's eye, I was seeing the S/C configuration. Sounds like your EGR has the same issue as mhamilton's.

Cheers,

Don

 

So I found 3 leaks from my initial smoke test:
1. EGR valve
2. PVC inlet pipe, o-ring at the air intake tube--old o-rings had taken a set and were no longer sealing
3. Air intake tube to throttle body--the clamp was not in the correct position (there is a notch where the screw goes at 3 o'clock) and was not tightened sufficiently

My fuel trims "before" were around +7-9% both banks. Well below setting a lean code, but enough to cause drivability issues at idle. Jaguar's TSB for pinging states that any fuel trim beyond 6% points to a leak that should be fixed, so for whatever reason our engines are particularly sensitive to any minor leakage.

I fixed items 2 and 3 and now my fuel trims are around 0 to +3%. The main issue I had is gone.

chrisb07, as you noted in your first post, searching ("EGR valve leaking during smoke test") I also found that smoke leakage through the EGR is very typical. The seal between the EGR pintle shaft and the body is just metal-on-metal, so probably every engine you test will show leakage here. However there is no definitive measurement of how much leakage is acceptable. There may be a point where it's too much. If you have no other leaks, then yes, it may be time for a new EGR https://www.scannerdanner.com/forum/...ak-issues.html

Did your smoke test show any other intake leaks? I would not jump to replacing the EGR unless you've verified no other leaks. It may be tricky to see some of the intake leaks from the lower gaskets. The amount of fuel correction points to either a much larger air leak or under fueling.

EDIT: well nuts... I spoke too soon. This afternoon driving the car I could tell it was acting up again, lugging at idle under load, and ST trims are bouncing up to 9%. Perhaps a smoke test while hot will reveal something else I didn't catch. Or maybe it is the EGR. The fact that it changes makes me think that is possible, obviously as the pintle moves up/down it may land in a spot that leaks worse than another.