Seasonal Check Engine Light

I have a 2005 Toyota Corolla CE with 80,000 miles. This car has been great and has had no mechanical problems except one. Last winter, my check engine light came on. Shortly after that, I noticed that when I started the car in the morning for my morning commute, it would run a bit rough at idle until it warmed up and then it was fine. I did get the code scanned and the message was that the engine was running at full rich which I was later told usually means the mass air flow sensor is caput.

Because I am a pilot I am gone for long periods of time and did not get around to getting the car looked at during the winter. As the weather improved and it got warmer out, the car started running fine at idle and eventually the check engine light (now sure I wasn’t paying attention) gave up and went out. Naturally, I went along my happy way feeling as though I had triumphed over Toyota.

Now that it’s getting cold again, the check engine light as decided to make another attempt at getting my attention and the roughness is started to return on very cold mornings.

What about the temperature do you think is causing the problem?

Incidentally, like many of the pour souls in Car Talk puzzlers I have a pack of gum, three matches, a cordless drill and a stainless steel cheese grader at my disposal for repairs…

Why do people have to guess at the most expensive sensor-- the MAF (mass air flow sensor? I like to think cheap–like the ects (engine coolant temperature sensor). Give that a thought.

Would a failure of that sensor cause the engine to run full rich? The reasoning for the MAF was that the engine will fail to full rich if the MAF fails to avoid damage due to a too-lean condition.

I suggest you stop by you local car parts store. Many of them will read the code for free. Then come back here and post the actual code as a reply to your original message. It should be in the format [P1234] Don’t bother with the english translation, the number is more important.

As noted the code only tells you why the light came on, this or that signal is too high or low etc. It does not say this or that part is bad. Keep in mind that most any problem with a car can be caused by more than one cause. Like running out of gas. Maybe you ran out or maybe the pump died.