rough idle on 260E
 

My 260 is constantly giving me problems. I still have not resolved the previous problem of almost dieing. Once I start the car, it drives fine but once it hits 80c, it starts to putter. It wont break 20mph and even if I am coasting, the economy meter is at full fuel consumption. Then after a few min, it clears right up. But, now, the idle is very rough, enough to rattle the dash. Anyone have any sugestions? The car seems like its getting too much or not enough fuel. Also, when its puttering and I get it going enough to shift, its very rough.

I am getting exactly the same with my car and I am searching for months and changed a lot of part that did not solve the problem.

Will be interested by any solution.

My guess would be a vacuum leak.

yes, vaccum leak for sure.

My 190 idles rough as well, replaced motor mounts and every vacum connector in the engine bay as well as the heater valves connector. My idle smoothed up but still has a little shake to her. I am thinking now it is one of the two connectors going to the tranny, the one on the modulator and on the intake. Those are the only two I did not do along with the ones inside the car. The ones inside I checked and seemed fine, I did not check the ones in the center yet because there is a lot of crap to remove first. So I would check all you vacum connections, most of mine were dry rotted and starting to get little holes in them.

also, when i fisrt start the car, even if the engine is warm. It idles very low, less then or at 500 then dies. After this, i restart and it runs fine. I have not checked my vacume tubes because, I dont know how. I might buy new plugs today, what kind are best for this model?

Get regular Bosch copper plugs especially since your car is not running perfect yet. For now do not get platinum plugs even if "they" advise you to get them.
While you're at it check some easy things like the vaccuum connections that go into the firewall above the brake booster, follow the lines see if you see anything disconnected or torn, check the fuse on top of the OVP relay (red relay behind the plastic shroud behind the battery) it will probably be ok but it can't hurt to check.

well darn, all they had were the bosch sing electrode platinum, so I bought those. ill check the OVP relay and vac lines tmrw morning. Also, the overflow line on my coolant tank is totally slit and rotted, could this effect it? The guy that owned the car before me used 87 and I have been using 93 and the problems didnt start until I got it. I doubt that caused all of this but could it of? What color should my brake fluid be, i put in DOT4 and it was clear.

are you saying running on 93 octane brought out the problem? if so, switch back to 87, it's cheaper gas anyway!

ill try it, i wasnt sure if it caused the problem. also, on the top of my air cleaner, there is a hole that is open. It leads to an inlet in the air cleaner. Should there be a hose or some thing here, or is it normal. Does it let dirty air in?

that "hole" is where you adjust the fuel-air mixture. leave it alone until you fully understand how it works. do a search, tons of reading material.

vacuum connections
 

Could someone throw more light on these vacuum connections. I was under the impression that the only engine vacuum connections were either side of the Idle Control valve, are there more?

The tubes mentioned above that go into the firewall above the brake booster. what are they for?

I get the impression there a vacuum connection to the automatic transmission. Is this correct and presumably a manual version would not have this.

It would help in a search for vacuum leaks if we knew where and how far to look.

Thanks in advance

Re: vacuum connections
 

My 260 E had the exact same problem. Idle would fluctuate, etc. Additionally, I would have jerky acclerations at low gears.

The problem was solved:

protector relay replaced
new injectors (6)
new injector seals (6)

The infamous idle problem....I had one and I hope I fixed it. I took off the air filter and was prepared to clean out the ICV. With the air filter off, it was obvious that one of the vaccuum lines was disconnected. After I reconnected it, the rough idle resolved.

It took me about 6months to figure this out. I could have fixed it earlier if I just took off the filter to simply look and double check all the connections.

My point is start with the obvious and cheapest....fuses, motor mounts, visual inspection, cleaning out the ICV, etc.

Yeah mine cleared up a little. But I need to figure out how to properly set the IAC. Mine got turned stupidly by me at one time and I have been trying for the last few months to figure out and fix it. I think I got it today. I have replaced all vacum connectors under the hood and the one for the Heater Valve. Several were dry rotted and had pin holes in them. Replaced all the rubber hoases connected to the IAC as well since they were cheap. Now I have new plugs on the way and air/fuel mix perfect but there is still a slight idle issue. It is smooth RPM wise but I can still feel it a little. We had anothe 1986 190E 2.3 8 V go through the auction last week and I saw and heard it run and it was smooth as glass. So I know eventually I will get it. Also replaced all motor and the tranny mount as well. All helped a little but nothing that has made it perfect yet. Anyone have any ideas. I have also replaced the cap, rotor, wires, drive belt, tensioner, and all the sensors in the sensor block by the thermostat. Still has this little issue that I can't seem to get rid of......