check engine light 87 5ks

[Frank Walian <walian@worldnet.att.net>]

Hello all,

    I have an 87 5k with 118k miles on it. As I was driving the car
today the car started sputtering and the tach would drop from 3400 -2200
RMPs. The car started running fine after a while but the check engine
light came on. What is the most probable cause of such a problem. I am
pretty sure the gas is fine. Is there an electrical reason this could be
happening? What symptoms does an O2 sensor give?

    I want to fix the problem and sell the car. I don't want to put much
money in the car so I rather invest time checking the car instead of
just replacing parts until I find the error. I just purchased a much
newer Audi A6.

    I just looked a the kelly blue book value for my 87 it says that it
is worth $3400. I find this somewhat unrealistic. What is the actual
value of a decent 5000k with leather and trip computer.

Thanks in Advance

Frank