My wife calls as she and our daughter are coming to meet me for dinner. The yellow silhouette of an engine has shown on the dash. Her first concern is if they are going to arrive safely at their destination, I assure her that it since it is still running it will likely remain so. She asks what the normal temperature should be and states that it seems low. Whew, I relax, not overheating is better. I ask her to drive the car into the workshop.
During the fifteen minutes it takes them to weave through the summer road construction and the resultant traffic, I am making my mental list of things that I should double check when I interrogate the cars computer with our diagnostic tool. There are two trouble codes present, the first indicating that the car is running too cool for what is termed “closed loop operation”, the second for a damaged air/fuel ratio sensor. I checked the temperature of the engine 186 F, well that is easy, a new thermostat will raise that back up to the acceptable range of 196 to 210 F. The second really was no a big surprise either, the last time I had scanned the car that sensor had been a bit on the lazy side, but that was 6 months ago. The result of both of these trouble codes is that they have the potential to waste a lot of fuel. Closed Loop Operation adjusts the fuel mixture to the programmed desired air/ratio to control emissions and fuel economy, the only other mode is called Open Loop Operation and is a condition where the engine is warming up or is nearly full throttle where it needs more fuel than the ideal ratio. We had noticed that the first portion of this tank of fuel was depleting rather quickly but had not put 2 and 2 together yet. We would have noticed when we reset the trip meter and calculated the mileage, but to catch it mid tank was even better.
You must wonder why I didn’t change that sensor before, well I wanted to get the most mileage I could from it. Air/fuel ratio sensors are not cheap, even if don’t purchase them at the Toyota/Lexus dealer the correct part for this car will cost us just under 190 dollars, each, and while only one is bad now we are going to replace both. This type of sensor lives a tough life, it is subjected to extreme heat on one side, up to 1400F, and our environment on the other side having salt and water from the road and the ambient temperature swings. It is really amazing that they do hold up for approximately 90,000 miles.
With gasoline approaching $4.20 a gallon, creeping like an auctioneer begging for that final bid, the prices at the pumps are strapping all of us. Our car repair is one of the cases of fix it or park it, the collateral damage from ignoring it will cost much more. A catalyic converter, excess fuel used, conscious cost of the enviromental toll all weigh in heavily. Overall we are spending an average cost per mile, for maintenance and repair, of 6.25 cents per mile, right in the average range for this make and model. For those of you who have not computed the cost of your car, simply take the cost of repairs and maintenance and divide it by the number of miles driven.
