Hello,

I have read most of the posts on this site pertaining to “Rough Idling” and have applied them where appropriate to my specific problem.
I am now getting to the end of the line with this issue, and my wife is getting upset with me.
Here is where I’m at……………..

I have a 300ce/1989 Calif. model , with 200k miles. This has been a great car with the usual on going maintenance. The oil and the filter have been changed every 3k miles and basically this car has been well looked after. Just recently the car started to run rough at idle to the point that my wife was scared to drive it. Before it was as smooth as silk.

When we first bought the car [100k miles] it would randomly stall usually on de-acceleration.
This was fixed by me with a combination of, fuel pump relay, OVP relay, Idle control valve, De-acceleration/idle micro-switch and the 4pole temp sensor, the last one on the head.

So here’s where I’m at with this newer problem to-date…………….

1] Replaced the EHA valve it was leaking slightly though the valve body. However leaked from the “O” seals at first.

2] Replaced the spark plugs, it was time. These are the Bosch ones that are recommended for the car, with the .035 gap.

3] Replaced the injectors with seals and holders, again it was time, these were the original ones with 200k miles. Seemed to run smoother when I got going.

4] Replaced the O2/Lamda sensor with a universal type, again this was time, 200k miles.

5] Adjusted the air/fuel mixture using the Lamda sensor as my input guide.

6] Checked the fuel pumps[2 in series] for operation appeared to be ok. When you put your hand on them you can feel the operation and here the wine.

7] Checked and cleaned the Idle control valve appeared to be Ok. This is relatively new item.

8] Checked the Air Flow Sensor appeared to be OK and was within specs. This also is a newer item.

9] Checked the air throttle control flap switch for idle and full throttle again worked OK

10] Cleaned the intake body around the air throttle flap.

11] Replaced both the new spark plug and ignition leads with an older good set, no change. Also checked the spark, appeared to be OK.

12] Checked for leaks using propane gas then again with soapy water, disconnecting feeds and plugging them. The feed that goes to the air conditioning appears to be open. So did the Charcoal emission circuit . I tried using my Mitivac on these but could never get any pressure? Also disconnected the Brake Booster feed and plugged. However this didn’t change anything on my inlet manifold when plugged.

13] Checked the vacuum pressure on the Fuel Pressure Regulator with my Mitivac seemed to be OK. I don’t think this the correct test for this unit. At least it held the vacuum.

14] Replaced fuel filter around 5k miles ago

15] Checked the car at night[pitch black] to see if I had any arching.

16] Checked the inlet manifold with a Vacuum gauge, no apparent problems her thought the rpm range. A manifold leak would show a low steady reading.

17] Disconnected the start valve electrically to see if it was leaking. However it could be stuck open very slighty. But the Lamda readings didn’t show this.

What needs to be checked is as follows………..
1] Cylinder Compression. This hasn’t been done yet because the car is so strong in acceleration and has lots of power.
2] Fuel pressure and double check the FPR as indicated in 13 above
3] TDC sensor
4] Hall effect sensor
5] Altitude correction sensor
6] Double check 4 pole temp sender.
7] Cylinder Leak down test
8] revisit the ignition.

Well that’s about it for now, I’m still working this problem and will go back and revisit some items.

I have one question regarding the valve adjustment. I know on the diesels, I have three that the valves tighten up over time. Does anybody know if this is the case with hydraulic ones. Occasionally I get a loose one for a few seconds on start up and then it fills up and goes away.

Any ideas would be appreciated

Brian
300CE, 240D, 300D Euro, and a 300SD