My trouble codes! Yesss...

[Fkyx]

Okay... so the weather was nice today, and so I decided to check my codes. Left the battery unhooked for 15-20 minutes before hand.

22, 23, 24, 49

First thing that seemed strange is the 49. Wrong airflow sensor? This only came up after the day I changed my plugs and checked the MAF. I tried to start the car a couple times after forgetting to plug the MAF back in and it died, naturally. I plugged the MAF back in and next time I checked the codes, 49 was in there. That was about two months ago... and the code hasn't gone away.

22 and 23 have been around for a while... still trying to figure out how to resolve those without spending too much money (and the knock sensor is really hard for me to get to with the TMIC in the way). Could 23 be related to the new 49?

24 is new(ish)... I don't actually remember how long ago I noticed it. I do notice that when the car drops down to 1k and below (at rest), the RPMs aren't steady. My Haynes says the IAC valve could have an impact... which makes sense.

Also, when out of gear, as the RPMs drop to and past about 2k, I hear a strange sound from the exhaust, almost like when you light a butane torch (minus the hissing).

Lastly, my mileage is pretty bad. I was getting around 12mpg when I would lug it around town and only hit it hard every once in a while. I replaced the fuel filter and the air filter recently, and now I get about that driving the car a little harder, and I actually hit 15mpg on the last tank, where I drive conservatively for a couple days and then went out in the dirt for fun a couple of days.

Advice on what to do would be appreciated! Thanks for reading, anyway.

[asc_up]

Have you tried clearing any of the codes by doing the thing where you plug in both connectors and then drive around for a minute?

Maybe some of them will go away if you do that...

[Fkyx]

Didn't know about that method. I'll try that when I'm on my way to track practice.

[asc_up]

Ok. Well here's how to properly do it with that method:

Start with both connectors disconnected, start the engine, allow it to warm up, then turn it off. Next, connect the green and black test mode connectors. Turn ignition to ON position without turning on engine. Depress the accelerator pedal to floor, return to half throttle and hold for two seconds, then release. Start the engine. Now the light can blink in two different ways. If everything checks out so far, it will blink to indicate a number 01, 02, 03, 04, 05, 06, 07, or 08. If a problem is already detected, it will blink accordingly. Either way, your next step will be to drive the car with the test mode connectors connected. You must drive over 7 mph for at least one minute, and shift up to 4th gear if you have a manual tranny. Now, either you will discover your trouble codes, or you will have none.