Inconsistant E320

[propaneman]

I own a 1995 E320 w124 car. I have spent the greater part of this last month diagnosing the vehicle (incl. checking fault codes under the hood and trying my best to rid myself of them). From what the car used to be, it’s come a long way. I am now at a point where I’m stuck (not that I haven’t felt that way before). I have replaced:
- Spark plugs
- Plug wires and/or coil packs
HAVE NOT REPLACED OVP relay
- Checked engine wiring harness (verify by opening the harness at the coil pack connectors)
- HAVE NOT REPLACED ETA (electronic throttle actuator).
- Proper Mercedes Battery
- O2 Lambda Sensor
- All the Injectors
- Fuel Pressure regulator
- Fuel pump
- Oil & Filter
- Fuel Filter
- Air Filter
- Checked the wiring harness for possible defects there. The harness looked good.

So the way the car is acting now is inconsistent. Anything under 1000 Rpm’s and the car sputters shakes and the engine revs up and down. It revs more in Park and neutral than drive however. Anything over 1000 Rpm’s and the car drives like a dream. No issues whatsoever over 1,000 rpms. The weird thing is on some mornings, the car drives perfect at all rpm’s. Other mornings, it has serious issues under 1000. It seems to me to be related to temperature. At cold and really hot temperatures, the car has issues (under 1000). At warm I don’t seem to have the issues as bad.

My thoughts are that I have a vacuum leak. Where do you start checking that? Should I just replace all the vacuum lines?

[Arthur Dalton]

What codes do you have now ?