1992 745 b230f- 185K

This is a project car that I have no records for. I have 500+ miles on it since installing a transmission, a replacement head, and the exhaust system.

I am currently chasing the cause of poor mileage. 19-20mpg is what I am seeing in combined driving.

I ran two compression tests and all cylinders show 190# To my untrained eye the plugs look like they are living in a fuel rich environment:



I did some reading in the FAQ's on O2 sensors I find that the Regina system does not use the Bosch sensor. That is what is in there because it came along with the used exhaust system I installed from a b234f.

I went back to the old converter/pipe to extract the old sensor and found that it is a Bosch as well- someone had installed the wrong sensor in the car (this setup also returned 19mpg)

So do you think two similar (but wrong application) O2 sensors are perhaps responsible for the poor mileage?

The proper sensor (3517394) is a bit pricey for the role this car is playing right now. Anybody know of any generic sensor replacement for the Regina cars?

Thanks for your thoughts,
Randy