1990 190E recent purchase ?
 

After totalling the 1989 190E I decided to buy a 1990 109kmiles. $ 1500.
Nice car the only issue so far is at idle and with the A/C on it idles erratic. Any ideas?
Otherwise it runs great.:)

It could be a multitude of things...

What is your idle speed before and after a/c engagement?

Thanks, I will check it out and post it.
New spark plugs, cap and rotor. same problem!:confused:

The hoses on the top of the engine often get brittle and become sources of vacuum leaks.

I will check the hoses, thanks.

I checked and replace the vac leak sources, rubber connectors. The car runs good when at speed but coasting to a stop light the rpms go down to below 500 to almost 0 rpm and then it tries to recover, it almost dies then it idles rough until you play with the gas pedal to get it to go, stumbles and after recovey it will run good until the next stop light.

Does this car have an idle controller?

I also sprayed carb cleaner around the intake manifold and vac hoses and did not get a rise on rpms. :confused:

Does the AC work properly? It may be a sign of a bad AC clutch, causing the idle to spike when the clutch releases, or drop when the clutch engages (and temporarily seizing the belt). Since it only happens when AC is in use, I would inspect the AC compressor and any electrical or mechanical items linked to it.

Thanks for the replies.

Actually the idling problem is occurring with or without the ac engaged.
It seems to go very low on the idle to the point where it almost dies when you get to a stop.

Check the idle air control valve. It's hooked up to the large air lines. If needed clean it out, sometimes it gets gunged up.

I would recommend AGAINST adjusting ANYTHING at this point.

Great post, thanks. I removed the idle air control valve and it didn't look gummed up or dirty but I sprayed it with a degreaser and now it runs great. Idle is steady at all stops, with or without the a/c engaged.
thanks.