The Pony Car Project-Hooray! The Light Is Out! Part 2

Several weeks ago, I smugly wrote a post about working on the Mustang and solving a problem with the Electronic Engine Control(EEC) system(The Pony Car Project Hooray The Light Is Out). The issue had to do with the Check Engine Light (CEL) on the dash that indicates an error with the engine. After writing that post, the  CEL would still illuminate after driving a few miles. Furthermore, when I ran a scan on the engine, I would get a Code 91. This indicates an error with the left side oxygen sensor. The oxygen sensor is a probe that goes in the exhaust pipe to measure the "quality" of the exhaust leaving the engine. The Mustang has two, one in each exhaust pipe. The oxygen sensors provide feedback to the computer that manages the fuel system to ensure that the engine is running properly, getting good economy and meeting proper pollution standards. But just because the scan indicated Code 91, it is always possible that some other error was causing the Code or once Code 91 was cleared than some other code could show up.

Today after I arrived home from Seattle, my order for Mustang parts arrived a day early. One of the items was a new oxygen sensor. I drove the Mustang up onto the ramps, crawled under the car and changed the sensor. It only took a few minutes. Then I went for a drive. And the CEL did not illuminate! I drove at least three times as far as I have been able to without the light coming on. After I got home, I ran another scan with the analyzer and I did not get Code 91. The only errors that showed up were "non fatal" codes that are related to equipment that is missing and not necessary for performance of the engine. Later in the evening I drove to Silverdale and back without the CEL light coming on. It seems to be running better and stronger too!

Maybe I have it fixed now!

 The faulty oxygen sensor. I do not know the brand, but was different than the Motorcraft item I bought. The various forums that talk about oxygen have recommended the Motorcraft ones.

Part of my Mustang parts order. The new oxygen sensor has already been installed. The fan is to replace the cracked one in the car. The metal parts don't look like much, but they are formed sheetmetal parts that rivet to the body and retain the plastic ground effect fairings. I also ordered new fog lights (to replace the missing ones), but they were back ordered and probably won't show up until the end of the month.