I recently started getting a service engine light. Got the code pulled and it was P0171 running lean. As of now I have basic bolt ons and a pro tune. I checked for leaks, couldn't find any. I searched around a little and found some people had bad o2 sensors and some had to clean their maf. I was just curious on how to check the o2 sensor and if it could just be an issue with the tune.

 

I believe I threw a lean code once and was (sometimes) running lean during WOT. Then I was retuned (by same tuner) and was running rich during WOT. I also had issues with idle bounce and a few other things.

I changed my FPR, replaced the maf, had a boost leak test, exhaust leak test, injectors flow tested, fuel pump flow tested, fuel pressure test, checked my plugs, and had a compression test.

In my situation, it appears my problem was the tune (protuned). I was recently retuned and the car is running great.

I would say get your tuner to check out the tune first. Then start checking the mechanical. I had my tuner check my tune and even retune the car. He swore up and down it wasn't the tune and that is why I wasted the time and money checking mechanical possibilities.

Hope you figure it out. It took me almost a year to finally give in and get a different tuner. But for me, the tune seems to have been the culprit.

 

In most causes that rear o2 can/should be disabled with your tune. Lots of people, including my self remove the stock o2 and replace with a wideband.

 

The OP is probably talking about the front O2.

 

Hey guys thanks for all the input. When I mentioned the o2 sensor I was just going off of what other people brought up. No one ever specified front or rear. My Evo is fairly new and only has about 6k miles on it so I wasn't sure if the sensors are known to go bad so early. I know one member on here said that in his case it was his tune.

 

Mine was because of the tune. I would throw a P0134 code when it was cold out and I threw a P0131 code once. I had other symptoms though.

The p0131 code is cause the car is running lean. I think usually this is caused from something mechanical (boost leak, fpr, exhaust leak, etc), or it's cause of the tune.

Search and read for the threads from people who had issues with their maf or O2. See if any of your symptoms match up. Maybe log (if you can) and send it to your tuner. If the car is running lean, then the car is going lean and the ecu cannot compensate for it. Your trims are probably off.

 

Just replace parts till it's fixed...

 

clean the MAF? doh! read the entire post. lol

 

The only maf cleaner I've seen says not to use it on mitsubishi vehicles. Not sure if there's another.

 

it's the tune, probably running lean with the weather change up. who did it?


your O2/MAF is fine I'm sure. You're probably just lean on start up or something.

 

I read here that it's fine. so i tried it and it was. CRC brand.

 

Good to know. I believe it was CRC

 

I just bought an 04 Rs and after two days service light went on. Code was P0171 and was told it was running lean in bank one. Planning on getting the car tuned Sunday and was wondering if it was from the tune or what it could be

 

I would get the tune done and see if that takes care of it. If you have a mechanical issue, hopefully your tuner will be able to recognize that something is wrong, while he is tuning.

 

ok thanks, tuning tomorrow so i'll find out then. ( the check engine service cleared by itself this morning )