Looking for advice on a mercedes problem

[thabenzclub]

I have a 95 Mercedes s-500 sedan with 95,000 miles. This car was running perfect but ever since I had a serious audio system put in the problems started. The trunk has 500lbs of extra weight from the system I had installed. Basically when the car first starts it runs strong, then after 15 min it has little power, doesnt go past 60mph, transmission shifts hard, and the temperature guage runs higher than it used to. Its been doing this for 3 months and has not got worse, but I drive it everyday and its difficult since its so slow now. Ive had bad luck with these cars when it comes to mechanics they all say something different and I lose alot of money. Its feels like im dragging a car, does anyone have any ideas?

[shorod]

Sounds like your car may be getting hotter than the PCM would like it to. Some cars have Cylinder Head Temperature sensors that will put the car in a reduced power mode when the sensors read higher than desired cylinder head temperatures. Essentially a few of the cylinders will be used like heat pumps to drop temperature, but this will result in decreased power since the engine will be a few cylinders down. I could see how the PCM may alter the shift firmness as well since a soft shift requires some slipping of the clutches which will yield more heat.

Did you do anything else around the same time as the stereo install such as flush the cooling system? Maybe there's an air pocket in the cooling system.

How old is the battery?

You should consider moving this thread to the appropriate Mercedes forum as well since they will be more familiar with the specifics of your car.

-Rod

[thabenzclub]

Thanks for your advice. Well because of the system I have 2 new $500 main batteries and the alternator is beefed up. I have'nt had any services done. There is this cable that I noticed that had some linkage broken, its on the top rear side of the engine. It looks like it controls the acceleration when you push the gas, if I push the cable with my finger it will make the asr light come on and it will idle crazy until I restart the car. Im thinking maybe that linkage got worse and is not responding right when Im pushing the gas. Thats the only thing I could think of so far.

[shorod]

With that new information re: the ASR light, you might find this page handy.

-Rod

[thabenzclub]

I just read that if the voltage drops below 11.5 volts it can cause various problems. I play my music alot and the voltage does have times when it drops low with the bass hitting hard.

Im thinking either the extra weight in the trunk is the problem,

or the voltage always being strained and dropping too low,

or that cable that has a plastic piece broke,

or the height at the rear and front being so different,

or the car has adjusted to the different driving habit from having constant weight to drag.

Ever since I took the 200lb sub box out all the problems stopped and now it drives normal. the only thing it still does is shift hard, but that might be because its used to pulling all that weight for so long so it shifts at a little higher rpm than before. Without the box it has more power, doesnt run as hot, and has been getting alot better gas mileage. The reason I dont thinks its because of the weight is because when people are riding inside theyre putting alot more weigh than my system, so why doesnt it do all this with people? Which would leave me to believe that maybe its just the constant voltage drop thats making things not work right. Any ideas on how I can pin point the exact problem? and if it is the audio system how can I avoid these problems from happening when I put the box back?

[shorod]

Do you have a stiffening capacitor installed on the amp power line for the subwoofer amplifier? If not, that will help.

Also, you could install the sub again, but drive for a couple of days either with the bass turned down or the volume turned down. If you don't experience a problem, but the problem comes back when you turn the stereo back up, you have a pretty good clue the current draw and subsequent voltage drop is the problem.

Going to a higher current alternator along with the stiffening capacitor would be good steps to take.

-Rod