#OxygenSensors

Joey writes:

Hello Sajeev,

I’ve been a reader of yours for years and greatly enjoy your style. (Woot! —SM)

My question is about my ’97 Mazda 626, with a hair over 215,000 miles on it, that’s been in my family for its entire life. It’s reliable, economical, and generally in good condition.

However, I am up for a registration renewal in October, and I need to complete an emissions test. I figured that it would be a good idea to check up on the codes behind the check engine light. The codes came up as an evaporative system and catalytic converter errors, which are both emissions fails.

TTAC Commentator Weltron writes:

Hi Sajeev!

The car I am writing about today is my winter beater, which is a 1999 Ford Escort SE sedan which says it has a tick over 155,000 miles. The problem I’m having with it is it it getting dreadful gas mileage. My average tank is about 19 miles to the gallon (in comparison that is what my twin turbo straight six Volvo gets around town). Over the winter I replaced both of the o2 sensors and got a marginal improvement (about .4 mpg).

And here’s the kicker: the dumb thing runs perfectly. No error codes or anything. Idles smooth and everything (well as far as Escort refinement goes). When I go on the highway (which is fairly often) I can see upward of 21… If I’m lucky.