"Check Engine" Light Puzzle - 1992 100

[Debu Purohit <purohit@mail.duke.edu>]

Any thoughts on the following puzzle would be much appreciated.

Four months ago, my 1992 100 (72,000 miles) was losing a lot of oil and
the mechanic
replaced the head gasket.  While they were at it, they also replaced the

O2 sensor and the timing belt.  They said the oil had gotten into
everything.

The oil leaks were stopped.  Now, however, the check engine light would
come
on in the evening under very specific conditions.  I would drive about 8
miles to work in the morning
and no light would come on.  On my way home in the evening, the check
engine light would come on after 1.5-1.8 miles.  After I stopped the car

and restarted the engine, the light was gone and it did not appear until
the
next day - no matter how far the car was driven.
This pattern was repeated over two months.

I mentioned this to the mechanic when I took the car in for an oil
change.
He checked and reset some codes.  Now the light is on ALL the time.
And he says that the EGR valve and the temp sensor probably have to
be changed.

Any thoughts on this problem and the recommended solution?

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______________________________________________________________________

Debu Purohit
Fuqua School of Business
Duke University
Durham, NC 27708
Office: (919) 660-8092
Fax: (919) 681-6244