Hello all, long time since my last visit. My 2005 VDP has recently began to flash "Restricted Performance" and turned on the CEL. Mechanic "fixed" it about a month ago - said there was a vacuum leak somewhere around the throttle bottle I think. Light came back on within a day or so.

**I have not had the codes read yet as it just happened today, but I will**

Edit: the codes stored were P0171 System too lean Bank 1 & P0174 System too lean Bank 2

In reading the forums, it could be anything from air intake, to ignition coils, to cam sensor, crank sensor, etc. So let me ask you a question:

Since the car is nearly 10 years old with 100k miles on it, what do you think about my replacing all coils, cam & crank sensor? Would likely cost close to $1000, but in reality, it's probably worth it if it keeps me error-free for the next 2-3 years. I know we are all busy, but I really dread going through the "hello, we know it's been a week, but your car is fixed," get there & have the light come in again a mile down the road. This has happened twice now (this time & the suspension issues, which I replaced with Arnott coils). I don't have the time to play "throw a new part on it and hope it's fixed" game. Love the car, & has been fairly trouble-free, so I don't mind throwing a few bucks at it from time to time.

Thank you for your comments.

Hmmmm....I also have had this recently, but.....

From past experience ( for me anyway ) its usually always when trying to give it too much stick from cold, when its not up to temp, which I hasten to add isn't something I do often.

In the Spring and the warmer Summer months I have had no issues.

Now in the winter time and temps really dropping, I notice it has became a more frequent issue, always easily resolved by turning off then re starting the car.

I'd read the fuel trims to see if it's an air leak, which with those codes it probably is. Changing coils won't help if so.

elm327 may work on these cars as they do on S-Type and start at about $10.

Finally, maybe I can help someone else on the forum!

1. Check and make sure that the air filter cover is on securely.
2. Make sure the hose from the air filter box to (what I think is) the throttle body is secured on both ends.

2004 XJ8 - not supercharged

I've had a very tough time figuring this one out. The first time this indicator came on, I eventually noticed that the air filter was upside down, and later realized that the lid was supposed to have clips keeping it tight on the air filter box. I fixed that with a zip tie, and the car ran better than it's ever ran...for about a month.

The indicator came on again, so I checked the air filter lid, and it was just the way I left it. Later I finally noticed that the hose leading to the throttle body (or whatever the first component is after the air filter) was just sitting up against the throttle body, but not attached. Put that back on and tightened it down, drove for about 30 minutes until the indicator went off, and my car drove like a dream, for a couple of days...ha! Checked and the hose had come off again. I don't think I snugged up the bottom side of the hose before, so I corrected and it's running great again.

Good Luck!

oh, and I have 180,000 miles on the car.

P0171 and P0174 showing up at the same time out of the blue is almost a guarantee of an air leak (actually unmeasured air-ingress). Air is entering the intake manifold w/o going through the air flow meter. I have 2 early 2000 ford trucks in the family and both had this problem and both had rotted out vacuum hoses. After having been replaced, the problem went away. Hopefully you did not spend that $1K on unnecessary parts. Get the leak sorted out first.

This post was very helpful thanks guys