I've been chasing the small vapor leak on my '06 S-Type R for the past three years. When I go on a long trip the light doesn't come on till I get back and get back to the stop and go traffic.

I've been tring to find information on if it's possible to trick or bypass the sensor to keep the MIL from coming back on. No luck yet. I'm stationed in Florida, and they don't do vehicle inspections.

As far as your rough idle goes, these supercharged 4.2s are very finiky. I noticed when I was getting gas on base (Air Force) or at the cheap Tom Thumb gas stations, I developed a rough idle when the motor was cold. As soon I swapped to BP, Chevron, and Exxon, my rough idle went completely away. Start off by throwing in a bottle of Lucas Upper Engine cleaner when you get down to half a tank. That way it's more concentrated.

 

TBH they're not at all finicky. A tiny few people have had P0442 and generally once someone who has a clue does proper diagnosis they fix it.

Rough idle points to a fault and I would NOT add that "engine cleaner" stuff. If you're tempted that direction use BG44, as Brutal et al (the techs) recommend.

I'd diagnose as a fault first. Watch fuel trims very closely or find a tech with a clue.

 

Did you ever get a smoke test done to find the leak?

 

Yes, and they couldn't find one. Took it to the Euro shop. They said they had the ability to open all the valves. I've got buddies that take their BMWs and Jags there and they do good work. It's so stinking expensive.

JagV8, I'm tell the guy what worked for me. I've had my jag for over 5 years and have put on 80,000+ miles. Every time I change my oil I also add Lucas in the tank. The only time I've ever taken it to a Jag dealership is when I stopped by to get a fuel cap. As soon as I stopped buying at cheap gas stores the rough idle went away. When I went back to using Tom Thumb and base gas the rough idle came back. Went back to BP and the rough idle went away again. When a supercharger is involved, perfect detonation becomes even more important.

Liquid Chris, obviously you can take it to a tech, but exhaust all the possible easy fixes before shelling out that diagnostic money.

I've been an aircraft mechanic for the last 23 years, so I know my way around a tool box and a multimeter. In the Air Force, it's all about staying on top of the scheduled maintenance as well as preventative maintenance. After you've had your car a while you know it's sounds and feel. Turn off the radio every once in a while and listen to your car.

I must say, I am embarrassed that it's taking me this long to figure out the P0442 issue but my state doesn't require annual emissions inspections, so I'm not pressed. The Air Force is giving us a four day weekend this weekend so maybe I'll go at it again this weekend. I'll post up if I figure it out.

 

Well.....ever since the one time it tripped the P0442 code after replacing the DTML pump it has not returned. I just filled today with Chevron, we"ll see if that helps the rough idle when it's cold. Hell, who knows, maybe the pump WAS the problem and that 700 mile trip seated the seals???? Maybe it will come back next month. The car runs frickin fantastic. It is a minor annoyance that is easily offset by the exhilaration I receive from driving this bad *** car. If any one on this forum bought one of these cars expecting the reliability a economy of a Toyota you are gullible (and that's putting it nicely).

DTML...How bout DMTL...frickin lexdysia

 

You getting your wocking murds fuddled?

The emissions stuff does seem to be a pain, and not just on Jags. The ridiculous thing is, I think more gas gets spilled at the pump than is likely to evaporate out of a tiny leak in your car.

 

Amen

 

Sshhh, don't tell CARB or EPA else they'll have laws and fines for those spilling fuel