Been getting the embarrassing puff of blue exhaust on my 2000 XKR. Would routinely ONLY happen after hitting around 50 mph; slowing down for any reason -- then a single puff of smoke upon throttling back up. Did the usual things like cleaning out the throttle body; cans of engine restore; thicker oil; even an oil catch can at the part load breather and then a second one at the full load breather (neither of which ever contained much oil). Not a gasket leak either as the smoke only happened as indicated. After all the attempts at a fix to no avail, I assumed it was either the dreaded nikasil bore wear; carbonized/worn rings; or worn valve seals and decided to live with it. Well long story longer, I ended up disconnecting the rubber vacuum hose from the supercharger bypass valve and taping the supercharger nipple for some other random testing and forgot to remove the tape and reconnect the hose. Boom, no more exhaust smoke -- at all. Car runs great -- still plenty of power.

Now i understand I won't have the benefit of the XKR and it supercharger boost, but since I'm long past the days of throttle thrills I'd rather have the break from the exhaust embarrasment! I've turned plenty of wrenches in my time and understand the basics of how the supercharger works, but I just don't see why this "fix" would work -- other than somehow the supercharger boost pressure pushing oil past marginally worn valve seals or piston rings... I just don't know -- anyone more knowledgeable care to offer some thoughts on the subject? In either event, I thought I'd offer this kludge to other embarrassed smoke-bombed XKR owners out there!

 

I second how embarrasing it is. Have a similar problem on my 2000 XK8; only happens when its been sitting awhile after a long drive. When I start it up, a big cloud of blue smoke emerges which then dissapates within about 10 seconds. After that, no visual smoke until I start it up after a drive. Doesn't happen after short drives. As you can imagine, it does use more than a bit of oil. Had a chipped exhaust valve and had a very complete valve job done including new guides and valve seals. Also cleaned out the metal mesh in each of the valve covers. No change. Having spent as much as I can reasonably afford (it is a Jaguar after all), I'm just living with it.

 

Valve guide seals....you want some oil seal expander additive in the oil or spend big bucks.

 

Thanks for the suggestion. I had a major valve job done about a year ago in which the both the valve guides and seals were replaced so I'm a little skeptical regarding an oil additive's ability to cure the problem. Seems to be caused by oil somehow leaking down into the cylinders when the engine is shut off after driving for about 1/2-hour. Shorter trips, hardly any smoke at all.

 

My 1999 XK8 has had the puff of blue smoke for the last 80KMI. It seems to only occur after a non spirited drive then a long cool-down period. I always assumed it was the valve seals. Oddly enough it is getting better over time and mileage. Weird.

TJ

 

I would definitely double check on that. A basic OBD reader can get to the manifold pressure reading and tell you for sure.

To my understanding, the bypass valve comes into play when you are accelerating under boost, and then you suddenly close the throttle and want to vent that unwanted residual pressure from the supercharger. If you disconnect that line to the valve, the bypass no longer occurs in that situation, but you should still produce boost (unless boost pressure keeps the valve closed?). In other words, it looks like your engine under boost conditions is not responsible for your blue smoke. That has to be good news.

I'd start with a good old oil catch can setup to see if there is oil somehow being carried through that valve line. You can also apply vacuum to the valve and see if it holds, or even if it pulls any oil.

Best of luck, keep us posted.

 

Thanks for the suggestions. Yes checked/placed vacuum on bypass valve -- holds perfectly. And I agree based on my limited understanding of how the SC works this doesn't make sense why it should have any effect at all (on oil burning/consumption)...

But it really does appear to be the case as I've test driven the car along the same path with the same/similar speed variations with and without that SC nipple capped and it reproduces the same result every time (uncapped burns oil/puff of smoke -at throttle up from deceleration upon hitting around 50 mph and no smoke with that nipple capped off). Its weird.

But hey, I don't have to understand it as I'm just happy to avoid the unintentional smoke bombs! I cam literally see the guys behind me cursing -- it'd be comical if this wasn't Houston where road ragers are triggered on much less

 

Were you able to check if that vacuum line somehow tees off to something else, like the fuel pressure regulator? Is that smoke excess fuel instead of oil?

 

Hmmm, I stand corrected... fmertz as you indicated -- that vacuum hose does indeed connect to what appears to be the fuel pressure regulator (will try to post a pic). It's a small silver can at the passenger side of the back of the engine -- with another small diameter plastic hose attached at the bottom. I did apply a strong vacuum to it nonetheless and it held perfectly so the internal diaphragm should be fine--but if it's fails in some other way/under certain vacuum throttle conditions as I described - I could see it possibly sucking in fuel and blasting that puff of smoke?

Idk it sure smells like burned oil when it happens -- regardless maybe I'll just replace that regulator and see it addresses the issue

 

On the face of it, the fuel pressure regulator should definitely be connected to manifold pressure. The entire fuel injection logic depends on it as it is based on time (how long an injector is turned on as a proxy for mass only works for a fixed pressure differential). Can you somehow get manifold pressure to that regulator only, leaving the bypass valve on the side for now? FWIW, a fuel pressure regulator issue is much more likely to be your root cause, vs. bypass valve.

Separately, you should try and get some "numbers" with a cheap OBDII ELM327 device. Manifold pressure, and fuel trims will tell you a lot.

 

Well MAP readings were from 6 inHg (24 kPa) at no throttle to 25 (80 kPa) on acceleration and about 14 (55 kPa) at steady throttle/cruise. STFT bw -.08 and .08 and LTFT at -4.7. Anything jump out at you on the MAP values? Is the MAP what you were referring to when you suggested checking manifold pressure or was that something else?

 

Your MAP numbers look plausible (+11 psi under boost) so it seems to confirm boost is still being produced.

For fuel trims, they are a function of load and rpm. You might want to turn on a recording function and see how they evolve under acceleration (and keep your eyes on the road).

On the face of it, with the fuel pressure regulator disconnected, you should run "rich" at idle (which the ECU will counter with negative trims), and lean under boost (positive trims).

 

Hi

I know this is an old thread, but was the root cause of smoke issue resolved with SC bypass hose connected.

Thanks

 

Unfortunately, no. Was never able to find the culprit. Tried everything short of valve job or ring replacement. Including various oil additives to help with seals and such. Car still runs good but only use it on short trips now as a second.

 

If no one else has mentioned it, full synthetic oil doesn't smoke as bad as regular oil under most circumstances.

Jack

 

condolances,,assuming the usual valve ,, head issues,,tho strangely A Family Kia early 2000s at an oil change was almost four quarts low w no sign of smoke or leaks,,the Corp told them there were "problems: with oil consumption,," in that series of engines,,being shocked by that w no sign of oil smoke etc it seems to be true,,a bit of reluctant info from them except with huge problems they were offered a new engine etc in case of meltdown,,that series of engines no longer being made