My 94 S320 was running great! A couple of weeks ago, I went to the service station to get fuel, and approximately 3 miles down the road it started rough idling at the light. I replaced the Spark Plugs & Fuel Pump Relay. I had the car checked out by my buddy whom services MBZ's (but he doesn't have all the test gauges/etc). He checked the fuses & Fuel Pump Pressure (it checked out at around 50 lbs) & temporarily disconnected the Mass Air & Oxygen Sensor - and they all checked out. My car is still revving up-and-down when idling & black smoke is still being emitted. Also, my car now gets about 7 miles per gallon - when it should be getting around 20.
What do you think the problem might be? Coils? Spark Plug Wires? Injectors? ECM?
Let's hear your input..................... Thanks!
My 94 S320 was running great! A couple of weeks ago, I went to the service station to get fuel, and approximately 3 miles down the road it started rough idling at the light. I replaced the Spark Plugs & Fuel Pump Relay. I had the car checked out by my buddy whom services MBZ's (but he doesn't have all the test gauges/etc). He checked the fuses & Fuel Pump Pressure (it checked out at around 50 lbs) & temporarily disconnected the Mass Air & Oxygen Sensor - and they all checked out. My car is still revving up-and-down when idling & black smoke is still being emitted. Also, my car now gets about 7 miles per gallon - when it should be getting around 20.
What do you think the problem might be? Coils? Spark Plug Wires? Injectors? ECM?
Let's hear your input..................... Thanks!
Like most, my mechanic says that it will need replacing when we do the head gasket. Hopefully, this problem is not harness related. What do you guy's think?
Like most, my mechanic says that it will need replacing when we do the head gasket. Hopefully, this problem is not harness related. What do you guy's think?
Well,i was told that none of the shops that knows about wiring harness problem ,do the tune up,or even touch W140 with a ten foot pole ,if wiring harness wasn't replaced.
Just take a look at the sensors,cut your MAF insulation ,prepare to be shocked.
Well,i was told that none of the shops that knows about wiring harness problem ,do the tune up,or even touch W140 with a ten foot pole ,if wiring harness wasn't replaced.
Just take a look at the sensors,cut your MAF insulation ,prepare to be shocked.
So true, So true. I'm going to have the harness & head gasket replaced in a couple of weeks. Does anyone know the MBZ part# for the engine harness & the most cost-effective place to purchase one ??
You might check out the fuel pressure regulator. If the diaghram goes bad it can force raw gas into the intake manifold bypassing the injectors and fuel management. I had a similar issue and the $35 regulator was the problem. Do a search on pressure regulator.
Remember,that starter harness also has to be replaced,plus i would suggest you to rewire ETA.
scrapingscrap and JonathanWallin made posts on their rewiring,
You might check out the fuel pressure regulator. If the diaghram goes bad it can force raw gas into the intake manifold bypassing the injectors and fuel management. I had a similar issue and the $35 regulator was the problem. Do a search on pressure regulator.
Chuck, the Fuel Pressure Regulator was just replaced with a new Bosch unit.
The car still rev's up-and-down when idling.
Here's the Winner(or in my case, loser). The engine wiring harness needs replacing. Mercedes-Benz should be CLASS-ACTION SUED for the B.S.
Engine Harnesses from 1991 to 1996 (all models) that were installed!
94 S320 Rough Idle / Black Smoke 
Linear Mode
