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98 E320 idle pulse/hunt when cold

419 Views 2 Replies 3 Participants Last post by  Kajtek1
The sedan's idle pulses between about 1200 and 1400 rpm immediately after a cold start. About one cycle a second. Idle is steady at the full stop at the end of the block and for the rest of the trip. What are likely causes of the pulsing?

In contrast the wagon's idle is a little rough when cold but I'll attend to that later.

98 E320s sedan and wagon
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Those cars are computer-controlled, so something is making the computer work hard.
Scanning with advanced scanner might pinpoint the issue, but in luck of such - start with basics.
-new air filter
-new fuel filter
-new spark plugs if they are close to become due.
-check cats for proper operation.
-observe any leaks (cracks, disconnected hose) in vacuum side of the engine.
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