Rough idle on 86 190e 2.3-16v
 

My 16v statrted having a bad rough idle issue. It starts fine and idles a little rough but ok about 1000rpm in park, but as soon as you put in in drive it bogs way down, coughs, and idle goes way down and it tries to stall and die. I have recently replaced spark plugs, rotor, and distrib cap, but it did not help. I also drove in for a while with injector cleaner in the gas to try to clean it out, didnt help. Idles fairly well, not great in park, but as soon as you put it in gear it goes bad, low rpms, and it tries to stall. Pushing on gas pedal will keep it running, and once the car is moving, and not at a stop and idle, it drives fine. But as soon as you slow to a stop again, the idle gets rough and you have to apply accelerator to keep the car running til you can drive off again.
Please help.
Car is a 1986 190e 2.3-16v automatic with 100,000 miles on it. No other issues, starts and runs fine down the road, idle is bad.
Chris

Check the iacv and ovp. Make sure there are no leaks on hoses to the iacv, sometimes they get brittle and crack

Thanks
 

The ovp is the over voltage relay right?
Is the iacv the idle control valve?
Thanks.

Remove the iacv (idle air control valve ) and spray BRAKLEEN or carb spray into it holding one port closed. Then shake it vigorously. Then Do it again thru the other port. Shake it till its dry. Reinstall. Should start and idle rough for a few seconds then clear up. The slide valve gets dirty and binds, restricting air flow. I've also seen a rough idle cured by replacing the alternator voltage regulator! low voltage was the cause. With 100,000 miles the regulator replacement is not a waste of money or time. 2 screws hold it to the back of the alternator. Remove screws and it falls out. GENTLY install the new one, tighten screws. The hoses to the IACV can get brittle and not grip it well. I've used clamps on some to help secure the hoses.

1)OVP ?,an easy check ,fuse sit inside this piece ,located at the battery area.
2)Alternator making enough juice at idle ? pull the wire from the back of the alternator ,a regulator sets into this area ,has to metal rods that wear ,you can replace this for $25 while its still on the car ,pulled my alternator output from 12.5 ,no good ,to a healthy 13.8 at idle.This is very important to have the car performing well at idle.
3)tO FINALLY GET MY CAR RUNNING RIGHT I had to completely clean out and seal my rusty gas tank on my 190e cossie ,I then worked my way through the fuel system with a fine tooth comb.New fuel pump ,fuel filter ,cleaned the fuel distributer with sonic cleaner ,if you do this its important to ready a few threads off 190 rev for details .The easiest way to check for FILTERING ISSUES IS TO DEMO ,CUT OPEN YOUR OLD FILTER, you want to soak it in water the drain before cutting it open .Youll be looking for rust particles ,in my case it was like looking at a dirt road inside a can.It can also be just a weak fuel pump , if you just do these 2 things its something you wont have to worry about latter on. In your case you have 2 pumps.Very important to play it safe when working at a tank ,you can squeese the main feed line with a pair of lg vise grips to close off the gas and when you crack open the filter or pump lines you will see some spray so rags w/ gloves and always disconnect the battery!

still no luck
 

Ok so with this idle problem I did a little work on the car and tried a few things.
I have replaced the spark plugs, distributor cap and rotor, voltage regulator on the alternator, and the Over voltage relay. It still idles really poorly when the car is placed in gear ( drive or reverse doesnt matter) it idles well ( about 1000 rpm) in park but as soon as you place it in gear ( automatic transmission) it coughs and the idle lowers to about 500-600 and shakes and coughs.
I also cleaned out the idle control valve, it was dirty but after is was cleaned it didnt fix the rough idle. The engine starts well and runs ok at idle in park.
I am wondering if maybe I am dealing with a vacuum leak in a hose but cant seem to find one. Any ideas?

Check the air filter. Also, what is the condition of the spark plug wires? Pull each wire off the plug and look inside the boot to make sure that the silicone support is not worn causing the boot to become loose on the plug.

Theirs also a small fuel screen at the inlet to the fuel distributer ,small and easy to clog.About the size and shape of a fuse,carb cleaner soak for 30 minutes,then spray it out if dirty.