W140 '99s50 stutter
 

(195K miles) Always stutters at idle when is warming up. High pitch noise followed by stutter... high pitch.... stutter etc. Once auto is warm no more stutter; idle is smooth. Any ideas?

Thanks!!

Try to pull the codes.

code is PO410. When the high pitched sound come on there is one click from under drivers side dash(like a switch sound) then stutter begins and fade away after 10 or 15 seconds. It repeats this until engine is warm-between 8 and 9 on gauge; then it runs smooth. This causes the CEL to come on. When I travel which is often, I can reset the light and jump on the interstate and drive hundreds of mile without the light coming on. But once the auto has cooled and I come to a stop light it begins again.

MBD

Any Ideas?

P0410 is a secondary air injection fault. Might be a broken vacuum hose. The air injection valves are operated by vacuum from the intake which is switched by solenoids. When the car is cold, vacuum is fed to the valves to open them up and allow the air injection to operate. When warm, the valves are left closed (except for testing by the computer). I would say that your stutter is caused by a major vacuum leak from a broken vacuum line to one or both of your secondary air injection valves. Check all the vacuum hoses and connections on your engine.

Brett

Can this cause a reduction in gas mileage?
There are two plastic thin long straw like pieces that come off the drivers side and feed back toward the carb. Are these the secondary vacuum lines you speak of? They seem to be brittle.

Check the black rubber ends. . . those tend to dry out b/c of the heat and then develop hair line cracks.

With the high engine heat, the 'plastic' lines get "hard" but normally don't break . . . . don't try to bend them b/c they will crack. If you have, then it probably should be replaced.

The rubber ends are pliable and still soft. Does someone have a picture which shows where I need to check for the secondary air leaks?

At this point, I recommend alldatadiy.com. It will have all the diagrams and part location information that you need. It's relatively cheap.

Brett