On a 2004 XJ8. Smoke test in search of a vacuum leak.

I know its normal for the EGR to leak on some vehicles. Is it normal for this Jaguar EGR to leak inside the plastic top?

 

I smoke tested my other XJ8 and confirmed its normal for the EGR and throttle spring/shaft to leak.

 

Have you analyzed your fuel trim data at idle? That will tell you if you need to pursue the smoke test...

If you've verified fuel trims are off at idle, check the rubber 'D" shaped seals along the seam of the intake plenum. That's one common place on the 4.2, as well as intake seals.

Any fault codes?

P0171, P0172 don't necessary indicate a lean condition, if that's what you're getting. Try driving it around the block while monitoring your fuel trims. If you get wacky readings at throttle positions 2, 3 or higher, you may need a MAF. Again, very common on those...

 

It is normal. The vent holes are there to allow the EGR valve to vent vacuum pressure, allowing it to modulate its position. With no power applied to the valve, it defaults to the open position. If you tried running the smoke test again, but with the key in the on position, the vent should be closed on a properly functioning valve.

 

I doubt that's right - may have been for some cars but not these I think. The PCM wants to be fully in charge of what goes where and no leaks at all. Leaks are what foul the fuel trims and then P0171/P0174 codes flag if no specific EGR code.

Any Jaguar master tech chime in...