I need help. I posted this on the AWD site but maybe this is a better place for it.

Thank you to anyone who can help
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Check Engine light =4 th time in 6 months
posted by someone claiming to be GMurray on Thu Jun 13 23:02 2002

I have a 1999 V.70R AWD Station Wagon

I have taken it into dealership 4 times in last 6 months- each time it was said to be something different

in January- both Oxygen sensors were replaced after I complained about Running rough-Idle rough-black smoke coming from exhaust and buildup around tailpipe-

[oH 1st time a month earlier replaced Canister purge valve and added in line Filter]

1 weeks ago Engine light came on and Mass Air Flow Hose was deemed to be the cause.
Picked car up and drove 35 miles with 2 stop s-engine Light came on.

left car with dealer for a week and was told today that they had put Fresh air hose on.[they credited me for Mass air flow]

Drove 20 miles and filled up at gas station-

Engine Light came on- drives like its 'missing'

Black smoke coming from Exhaust.

Does anyone have any suggestions.?

I am told that this Diagnostic is not 'exact science'

Help