I have an 03 S-Type 3.0L. I dont know if this is just coincendence or something happened but I called Belle Tire and they told me that thay could not align it because it had stabilazation control and they did not have a special tool to do the align. I called around and a garage said no problem to do the align, so I took it in and it was running great, Not one thing wrong. When I pick up the car, it is running rough at idle. I am getting a DSC error and a Traction control error and a gear box fault. I drive out and the car won't shift into third and is running all screwy. I take it back and they said nothing they did caused this. I drive the car home thinking I would take it in to the dealer. I park it overnight. the next day all the errors are gone except it is still running rough at idle. At idle the engine is running like it is missing on numberous cylinders. The lights go dim at idle and when I rev it the lights get brighter. It even does this in neutral. I got all the codes back again a few days latter so I parked it and put the battery on charge. The error codes went away again but is still continues to run rough and the lights dim and brighten when reved only in idle. It runs smooth as long as it is over 2000 RPM. I just cant believe all this would go bad all at once. Any help would be appreciated.

 

A hard re-set of the ECU may be in order. The shop may have accidently messed up something. I can't see how they could have done something serious? Mess with the O2 sensor wires? First check for codes, then hard re-set the ECU.

 

How old is the battery? Sounds a lot like low voltage issues. Modern cars do some really wierd stuff when the battery goes south. Trans code is common with low voltage. Numerous codes are common with weak battery as well as misfiring.

 

Yeah, could well be the battery. Maybe the shop just left the lights on (door open or whatever) and flattened it.

Otherwise you're probably looking for a disturbed vacuum line or wire or connector.

 

+3 battery check.....

 

Thanks, I kinda suspected the battery. I will replace it today and let you know if this solves the problem.

 

Well I had the battery checked and it was fine. I started to look around the engine compartment and discovered a small slit in a vacume hose connecting the crankcase vent line to the carb. I am attaching a pic of the hose. It was very inconspictious because it was a very small slit on the under side of the hose. I wrapped it with electrical tape very tightly and coated it with glue for a temp fix. The Kitty now runs smooth at idle...Imagine that!!!. Now I have to go to the dealer to get a replacement hose because I have had no luck locating one online. Thanks for the help and I hope this might help someone with the same problem.

 

Oh dear. And how was it checked? Do they understand modern car electronics & computers? Did they use a storage scope or the like while you cranked it from cold? No.

Expect more trouble if it's the battery

 

I would try Motorcars LTD before going to the dealer. With a few exceptions, dealers are ripping drivers off with the prices they charge. They charged me $22.00 for O-rings that I got at Motorcars for $1.94 plus tax.

 

I don't quite understand. You say you fixed a vacuum leak and it now idles. What happened to all the other issues?? I can't see a vacuum leak causing the dim/bright light deal.

 

Ditto to bodyman and Jagv8....doesn't make sense that a vaccume leak would cause electrical issues?

 

The vacume leak caused the engine to run rough at idle. The engine was running so rough that I imagine that the alternator was not spinning fast enough that it would cause the lights to dim and get bright. It was running so rough that it was like it was going to stall at any moment. The codes showed that there was misfire on about 4 cylinders almost stalling, 800 rpm then up to 1200 rpm back to 700 rpm and so on. After the vacume leak was stopped the car ran smooth, the alternator was able to operate at a stable RPM, and the lights quit dimming. The other codes that came up, IE: gear box fault, DSC fault and Traction control error, I don't know what was up with that. But I did charge the battery and I haven't seen the codes since.

 

Those other codes were likely due to the jerks of the engine (upsets gear box) and the voltage variations. To be expected.