NOTE LOOKED UP THE VIN - IT' S a 2002. Working on a 2002 E320 4matic, W211.282. 100K miles, deceent maintenance. Complaint was high and rought idle. Started off with codes for oxygen sensors, lean mixture, EGR malfunction. Replaced oxygen sensors and MAF as maintenance items. Now left with P071 (lean left bank). Idles in Park at about 1500, but here is the weirdness - if you depress the brake pedal, the idle speed drops to 750.

The EGR valves hold vacuum, and at idle the switch is not allowing vacuum to the valves. There were some minor tears in the hoses for the crankcase ventilation system, but nothing major. Spraying brake cleaner around the intake manifold and injectors produced only minor effects on the idle.

Anybody seen this before? I am thinking a bad brake booster, but the brakes are fine and it's been my experience is that a bad booster will increase the idle speed when the brakes are applied.

Thanks,

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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe