Afternoon all

I've been chasing a vacuum leak for a while now on my 4.2 XKR, symptoms are LTFT running at 7% / 5% on banks 1 / 2 respectively, coupled with a bit of a lumpy idle on cold start. Car runs well for the most part but feels a bit restricted, almost surging, when getting into the high gears under heavy throttle. Once I've brought the LTFTs down I'll be getting the catalytic converters checked because I've had code P0430 pop up 3 times in the last year... but I digress.

Using a smoke machine from Amazon I managed to find a leak on the brake booster quick release from the throttle body, which I have now rectified. Now I am running the smoke test and seeing wisps of smoke from under the throttle body. It's very restrictive to get a good view down there but I believe it's coming from the thing circled in the below image, where it bolts to the throttle body elbow :



My questions are :

1. What is it?
2. Is it possible for vacuum to be leaking from it?
3. Is it possible to remove, clean the surfaces and replace with the throttle body in-situ or would it be all together easier to remove the throttle body first? Clearly it would be easier with the TB out of the way, but is the TB removal easier than struggling to get to this other thing?

I'm about 95% sure the smoke was coming from the gasket between this and the throttle body elbow but of course, smoke has a habit of moving around.

Oh and please forgive the boob thing on top of the intake, it's a plastic tub from one of the wife's multitude of beauty products coupled to a silicone tube to get the smoke into the intake for the testing. Seems to work well...

Thank you,
Simon

 

That's the egr valve. No vacuum connections there. It seals against the rear of the plenum, but I'd consider that an unlikely leak location.

Besides the vacuum hose you already corrected, there is a small rigid vacuum pipe that snaps in to the right side of the plenum under the throttle body. It seals with an o-ring. That was a leak source for me previously.

 

Thank you. Looking at some guides on removing the throttle body and it doesn't seem to be beyond my scope so I will do that when it gets light, at least that will give me some more access and hopefully make it easier to figure out where the smoke comes from.

Again it's only what I thought I saw with mirrors and torches, but the smoke appeared to be coming from this part of the EGR valve; I don't see any gaskets available apart from the metal crush ones for the exhaust tube, but it definitely looks like rubber around mine :



Could vacuum be drawn in there?

I'll have a look for that pipe you mentioned when the TB is off; just to clarify, is it on the same side as the EGR/photo in the opening post or the same side as the brake booster line?

 

At the upper left of the image you can see the flange where the throttle body has been removed.
just beneath the flame edge you can see the plastic vacuum line where it is plugged into the plenum.

 

Thank you. That looks like the quick release from the brake booster which I already replaced, but I'll get a better look once the TB is removed.

 

After a bit more clicking around I noticed some talk of EGR solenoids on the XJ8 4.2 which do vent some smoke during a smoke test and it's quite normal. Can anyone confirm if it's the same on the XKR X150?

 

Well I bit the bullet and removed the throttle body. Wasn't difficult at all. With it out of the way I was able to see much more clearly and it certainly looks like the smoke is coming from the EGR, I took a video while I was in there :


Before spending the asking price for a new EGR when mine is still operating, I undid the two bolts holding the solenoid and removed the top half of the unit, cleaned the surfaces and sealed it back up with RTV sealant. Nothing lost apart from some time if it doesn't work, but hopefully a better running car to gain. I've left the RTV to properly cure and I'll do another smoke test in the coming days while I wait for my new TB gasket to arrive.

 

Did a quick smoke test today during my lunch break (working from home is just the best), but to my dismay there is still smoke coming from the EGR solenoid. This time not from where the solenoid bolts on to the water cooler, but instead it seemed to come from the plastic plug/socket where it is attached to the side of the solenoid wall. I am assuming that level of disassembly is ill-advised or perhaps impossible, however I again disassembled the EGR and this time ran a bead of superglue all around the plastic plug and the plastic "gasket" which sits between the solenoid and the water cooler in the hope of plugging whatever leak there may be. Truth be told, I also saw smoke coming from the pins within the EGR connector before I noticed the silicone seal inside the loom-side plug and connected it up.

If the next smoke test still shows smoke exiting from the EGR then I may be facing buying a new one. But before I do, would someone who has done smoke tests on these cars please just put my mind at rest and confirm whether or not smoke should be vented from the EGR? I've never seen this mentioned on any previous XKR vacuum leak threads before, but the mention of EGR vents on other forums has made me want to seek some peace of mind from someone on here who has looked for vacuum leaks : has your EGR vented smoke during the smoke test?