This Nerd Heard…

Ok, after reviewing the previous charts a few times, I decided that the Mass Airflow Sensor and the second Oxygen sensor were not behaving the same when my check engine light would turn on. That is to say that I could follow the two graphs and they tended to behave the exact same way when everything was normal. When the problem would occur, my MAF sensor was indicating that the air intake was decreasing while the second oxygen sensor was indicating that oxygen was increasing. This suggested to me that the MAF was not reading the amount of air properly and so we were running lean, which caused an upward spike of available oxygen in the air.

I bought a reconditioned MAF sensor for about $80 + $50 core and replaced it on my car. It only takes about 5 minutes to do. I reset the computer and took it for a test drive. The performance seemed better at the time but it was hard to say because the computer had to readjust itself.

It has been about 220 miles and two week now since I replaced the sensor. The cars performance is good, it accelerates more smoothly and has more power. I haven’t put in a new tank of gas yet, so I have no idea if the gas mileage has improved.

So, if you have this problem and cleaning the MAF sensor doesn’t seem to work, that does not mean that the MAF isn’t the problem. Mine seemed to completely malfunction randomly and cause horrible performance. The gas mileage had dropped significantly even though the check engine light didn’t always turn on.

Alright, I got a more sophisticated ODB-II reader. I borrowed it from my brother. I was able to get more advanced diagnostic information as I was driving the car. I took a reading of “normal” sensor data. It shows the engine RPM, the mass air flow, and the output from the 1st and 2nd oxygen sensors. At the time this capture was made, the car was going from about 65mph to a dead stop.

The second capture was taking within a minute or so of the check engine light coming on. I’m going approximately 65mph thru the duration of the entire graph.

I spent a lot of time on the road this weekend and had the opportunity to share it with some rather good and mediocre drivers.  I’m not the type of person who would try and cause any sort of harm to any of my fellow drivers, but I do get kind of upset when people do things on the road that don’t make sense to me.

I’m offering some tips on things people can do to make themselves better drivers (at least in my eyes).  These tips may not be legal, may not be safe, yada yada yada.  Follow them at your own risk.  If you disagree, please feel free to post a comment.  I’d love to know what others think is better.

• Don’t drive in the left most lane on the freeway.  Even if it is only a two lane freeway, you really ought to stay to the right unless you are passing someone.  Of course, if it is bumper to bumper traffic, this rule doesn’t apply.
•  If you are going faster than the car in front of you, do not wait until the last second to move over and pass the car.  Look far enough down the road so that you have room to speed up or slow down in order to merge with the traffic next to you. If you have to slow down to the speed of the car in front of you, wait until you will not cause more “aware” drivers to suffer for your inability to look a safe distance ahead.
• When you are changing lanes, MERGE with the traffic next to you.  You are not merging with traffic if you are going significantly slower than everyone you pull in front of.  You are stopping traffic.
• If you are only going a few miles an hour faster than the car in front of you, don’t make other people slow down significantly so that you can take a decade to pass that car.  It causes people to slam on their brakes and may cause an accident.  It also causes people to label you with terms that are not nearly as polite as “inconsiderate” or “thoughtless.”
• When driving on a down hill stretch, do not brake in every turn.  It is hard on your brakes.  You are also far more likely to lose traction if you brake while turning.  Instead, use cruise control when possible and set the speed such that you don’t need to brake at all.  If there is an especially sharp turn, then brake before the turn. It is safer and will instill more confidence in those around you.
• Don’t get all over someone’s bumper just because you like to see another car in front of you.  I can’t tell you how many times I had someone get all over me and then not move an inch forward or backwards after I get out of their way.  Worse is when they move forward just enough so that I can’t get back over to pass someone in my new lane.
• When making a right hand turn, turn into the right most lane when possible.  If you’re not driving a semi-truck and you can’t turn into the right most lane, you are driving a car that is too big for your driving skills.  If there is a gap in another lane that is safer to turn into given the conditions, feel free to do so.
• Do not make everyone behind you wait for you to turn right into the left hand most lane. I don’t care if you want to make the next possible left.  It is inconsiderate, selfish, and bad for the environment. Just think of all the pollution created by those people who are stuck behind you unable to move because you want to make a quick left into a grocery store.  Not only that, but if the traffic is so bad that you have to wait 10 minutes to make that turn, you could have gotten to your destination faster by making a U-turn.  Your car produces almost as much pollution sitting there idling as it does moving.  At least you are getting somewhere when you are moving.

If I have any more tidbits, I’ll add them on after this point.  If you’re guilty of any of these offenses, don’t worry, I don’t hate you.  Just go and sin no more.  With your help, we can help curb road rage and make the roads a better place.

So the P0171 check engine code seems to be a rather popular code. I’ve searched the web quite a bit and most people who see the “Check Engine” light come on their Corolla have this code. It seems that this code usually comes up after the car has been driven 70,000-80,000 miles.

Common advice on the internet suggests that you clean the mass airflow sensor and see if that fixes the problem. The problem could also be caused by a faulty oxygen sensor or a vacuum leak. The corolla has two oxygen sensors. I haven’t looked to see where they are located but one is probably in the exhaust manifold and the other is after the catalytic converter.

So what is the cause of my P0171 error code? I don’t know. The ODB-II reader I used was one that is only capable of checking engine codes. I’m thinking about buying this reader because it should allow me to run the engine and actually look at the output of each of the sensors. I’ve tried listening for a vacuum leak but I don’t hear one. Of course, that doesn’t mean that one doesn’t exist. I just hope I don’t have to replace too many sensors, they are about $100 each.