rough idle
 

i cleared all codes that i had. still getting code 19 but it running rough as if its missing then it would cut off an will not crank let it sit for a while an will crank with rough idle could the fuel filter be clogging up because i hear this hisssing sound by the filter n pump. the last time i tune it up was 3 or 4 years ago wires, plugs its a 94 e420:confused:

code 19 - Potentiometer throttle valve drive, Loose contact.

You should start checking the throttle actuator wiring, its wiring also disintegrates like engine harness. see http://www.peachparts.com/Wikka/M104WireHarness towards the end.

rough idle
 

thanks phantomlord but your motor is differt from mine from the picture that iam looking at plus i change my wire harness about 4 years ago or would that be my bottom wire harness

Silly question - do you have plenty of gas in the tank? Just because the gauge you do, doesn't necessarily mean you do.

I found that out the hard way this morning. My car died just as I pulled into my parking spot. I let it sit, and it started right back up, then coughed a bit and died. I let it sit some more, started it up, then listened to the pump; after about 10 seconds, you could hear a sucking, hissing sound for about 5 seconds, then it shut down.

Of course, it could also be due to a little flotsam in the tank blocking the strainer since the fuel level is probably at the right height to do so...

rough idle
 

yes got a 1/4 tank of gas in it dhjenkins i forgot to post that i can smell raw gas coming out of tail pipe. my hisses continually.

Sorry I missed it check http://www.k6jrf.com/MB_S500.html (Diagnostic Trouble Code #19)

I don't think a bad TPS would cause the vehicle to not crank at all.

Have you pulled the plugs to make sure you aren't getting coolant in the cylinders causing a temporary hydrolock or pulled the dipstick to make sure the oil isn't cloudy?

Of course, as far as the "no crank" situation goes, you could just have a starter or battery that's going out. A battery that's shorted inside can cause all sorts of weird problems. Does it get hot to the touch? Have you checked voltage running & not running? If it's a multi-post (side & top) battery, make sure you test the posts you're actually connected to.

I had a 4 post battery a few years ago that read a perfect 12V on the top posts, but the side post voltage, KOEO (key off, engine off), was jumping around from 6-12 volts all willy-nilly. Caused intermittent starts, rough running, random codes, etc...

rough idle
 

thanks dhjenkins
but the car will turn over once it quits got plenty of fire in the battery . ive read some post about the air temp sensor looked at mine looks gunked up with smut wire in it looks real dirty.

The 2 biggest improvements in idle for my 300E was the O2 Sensor and Water Temp sensor. Replaced all other items including OVP, Plugs, Wires, Voltage Regulator, Vacuum Lines, Distributor Cap, Rotor, and Coil with no change. Still need to try Idle Control Valve and then injectors and all the tough stuff. Once in a while, the idle still struggles for "I don't know what reason". Just my FYI Stuff :)

Did this problem start all of a sudden or did it get progressively worse?

Does it ever make it up to operating temperature? If so, does idle improve? have you done the nighttime water test on the plugs? What do the contact points on the inside of your distributor cap look like? The carbon formed on mine added anywhere from 7K-20K ohms resistance - a little dremel action took care of that.

What does your economy (vacuum) gauge point while idling? Have you checked your timing?

Pull one of your plugs and look at it. Is it black and sooty or white & ashy?

rough idle
 

runs good till it gets up to 80 degress then it starts to miss then it would cut off look at the distributor the contact on the inside were black got some sand paper that was fine n clean them off runs good but still has a little miss to it . do i need to get 2 new rotors n caps cars has 234,000 miles on it changed them about 4 yrs ago i remembered when i took it too the mc dealer that it showed they were always putting new ones on the car

Have you checked your engine temp sensor?

rough idle
 

thanks dhjinkins
no i havent chect the temp sensor how do i do it n where is it located