After replacing the bulb and ballast on my 2006 XJ8 VDP i took it to the car wash, got the brushless option. High pressure sprays, very high velocity air dry. Now the right side low beam flickers on/off, there is a headlight switch error message. It was a real pain replacing those parts, rusted fasteners didn't help.

On another subject, yesterday I got the car inspected, before the headlight fail, upon starting the car now will run roughly and stall unless I give it some throttle for a little time, then it will resume normal running. As a part of the inspection the OBD is checked, have they altered the idle map or some such thing by checking the OBD?

Thank-you, the responses I've gotten from this forum have been very helpful.

 

There will be numerous opinions on the rough idle (all of them very likely, as it is the symptom of many possible causes), however, I will make some conjecture and give you an opinion. I usually avoid using the Pressure Washer/DIY car wash anywhere near the front grill. I've noticed the 4.2 litre seems somewhat sensitive to getting high pressure water sprayed at the nose. Following a DIY car wash, I had the exact same symptom, when hot on a restart, after short drives, it would stumble at idle for the first minute unless I revved it up, then it would disappear.

My cure was; clean the MAF sensor, a very easy task, you will find numerous threads on MAF clean. In summary, its really easy, two screws and it's out, then spray with CRC MAF cleaner from Azone or Advance. Then one bottle of Chevron Techron. It (stumble) has never ever reappeared. since then, I avoid spraying upper and lower grill when I use the DIY Car wash or pressure washer.

Thanks to Rickkk for correction!

 

I think that you're referring to the MAF (Mass Air Flow) sensor which is mounted on the air filter ductwork. Yes, for a rough idle, cleaning the MAF sensor would be the very first thing that I would do.

 

Thank-you for your quick reply. The rough start actually preceded the carwash, it was right after the inspection. But the problem resolved itself, the engine runs fine today. The real problem is with the HID headlight, that persists. Looks like I'll be taking the front of the car apart again, yay.... Needless to say I won't be going to the carwash again, hand washes only from here on out. The good thing is that new ballasts aren't all that expensive, the OEM unit I got even came with a new bulb. Chrysler 300s used the same units. I just ordered a new ballast, under $50 shipped, including a new bulb.

 

Hi Threeducs33,
Also behind the headlights are some earth points. These are also affected by water spray. Gently try and loosen them and check for any corrosion. The studs are alumin(i)um so are fragile. Coat them with silicone grease and retighten (gently!) There are two earth points on one side and one on the other. Corrosion here can affect many systems, but the headlights are usually the first to be affected.

Pete M

 

Thanks, I just had them off though. I ordered a new ballast, comes with a new bulb, $48 shipped, the job shouldn't be so difficult as I now know what I have to do. I'll report back with results.