Bought a 2003 S500 last spring, and had a issue with the pre-safe system and did not want to go to dealer in fear of huge bill. Went to a indie, who was unable to find problem. I asked indie to drive the car over the weekend for an assessment of the newly purchased S500. The indie gave the S500 to his younger mechanic, and when I went to pick the S500 they had the look of trouble in their eyes. They asked if I had any running issues- I said no, they said you have some now. They did not try to troubleshoot the issue, just wanted to give me the S500 back. I suspected the mechanic beat the hell out of the S500 and something have.

The issue was the S500 would die at stop light, be hard to start, rough idle. All intermittent, except the hard to start. I purchased an aftermarket scanner and it gave a MAF issue, and running lean under partial on both banks. I replaced the MAF, thought the problem was solved, and sure enough 30 miles later CEL would come on again and I was having poor running issues, including hard shifting of trans.

I ended up replacing the Crankshaft and Camshaft position sensors, accelerator pedal, MAP, both diverters, vacuum hoses,and a few other sensors. After 30-40 miles, CEL would still come on, and it was still hard to start.

Read, read, and read more and could not figure out the problem. I though maybe intake manifold gasket leak, or maybe EGR valve. On a BMW board I saw same condition being caused by a fuel filter....

I replaced the fuel filter and it has been one month and a few thousand miles and zero issues. S500 starts up instantly.

Lesson learned- change that fuel filter first when having starting/ running issues on the W220. It is cheap, easy to do, and can prevent a lot of other potential troubleshooting steps. May sound silly- but I missed the issue and paid a steep price in time and money.

One very good benefit- this took my 8 weeks to fix and I learned a ton about the S500 and am no longer in fear of working on the vehicle, actually feel super comfortable with it.

 

Lesson to be learned - Never, ever give your car to someone to drive for a weekend unless you really and I mean really know about their reputation. Also, make sure to tell them that THEY are the only person you want driving the car. You are very lucky the younger guy didn't crash it into a brick wall. Try explaining that to your insurance company.

 

John,

You are spot on I should not of let someone else drive it.

Bigger lesson is the fuel filters on the S430/S500 can cause issues that reflect failure of many expensive parts and or labor to change including MAF, MAP, diver-tors, EGR, intake manifold, etc. I think if I had brought to dealer maybe they would of pin=pointed the fuel filter, or maybe they would of replaced all the stuff I did and charged me a train load of cash, when all it was a fuel filter (under $40) at fault.

 

Mike when things get real crazy have the dealer diagnose the problem and tell them you will fix it yourself. Sometimes it is worth the hundred or so dollars they charge to identify the problem. Based on the items you listed your bill would have been in the thousands at a dealer. The labor alone would have been about $2000.