Sixhorse

Hey All,

I have been having some issues with my S420. I have taken it to 4 mechanics and have came back with nothing. 1 said they couldn't diagnose it. 2 said it was a tranny, they were the same company though and I have my doubts. The other just said it could be a number of different things and didn't give a place to start.

The car has 130,000 miles on it. The problem occurs after it sits for a few days. A weekend of not driving, a holiday, ect.. After it sits for a few days, when I go to start it, it starts very rough. When idling in place, the rpms bounce from 1500, down to 200. Keeps doing that. Then when I hit the gas, it has a strong hesitation to go. When I hit the gas harder, it just sputters for a second and then takes off. Once I get going 15-20 mph and higher, the car runs fine. The problem goes away after 3-4 miles of driving and doesn't come back till after it sits a few days again. With that being the case, I can't get the problem to show up at the mechanic because I have to drive the car there. FRUSTRATING!

Had a similar problem a year and a half back. However, the car died and the mechanic diagnosed as a crankshaft position sensor and replaced it. Car ran great after that until now(Had this problem for 4 months). Also, I had the fuel pressure regulator replaced as there was a small leak. Thought that might have been causing the issue, but problem persists.

Other issues(Not necessarily related to the issue)-
-I can't control how high the heat is(always low).
-Light for the speedometer and rpms is out(gas gauge still lit up).
-When the radio is on, the speakers make a popping sound.

I haven't worried about fixing any of this stuff until I fix my main one.

Any suggestions, hints, ideas would be amazing!

Thank you

N2finances

I tune the car up work fine also change both coils too.

Gummee

In my case, I'm getting some leaking into #4. I'm not 100% sure if its antifreeze or oil. A new head gasket is a 'round to it.'

M

oldsinner111

poster sounds like you have wiring bad,and wires in throttle body bad.Have either been re wired?

86560sel

I had a lot of hard hot starting/rough hot starting and even once when it would not start. That went on for a year and I even parked the car and let it set for months. Recently, took it to some shops. One MB mechanic had me run a tank of seafoam and it cleared it out a lot - running fine now. Also another tech I took it to a week late said that the rotor buttons were a little corroded, cleaned them up and car runs like new again... at least for now. lol.

ibeforreal

I know this is an old post and I have a W220 S-Class Mercedes. However, I have a friend with a 1995 S320 and he is having the same symptoms described in your thread. On my W220 the CPS is rather easy to replace (takes about 15 minutes tops). Mine is located on the driver's side of the car near the firewall.

Is it located in the same place on the W140? Are there any instructions on here as far as replacing it? If it is the same then I know how it is done.