Need help with P0171

[mwill756]

Ok this has been driving me crazy, here is the situation:

'99 Protege, 1.6L, 77K
Only routine maintenance that has been kept up is oil changes
I think it has had one tuneup

About 4 weeks ago, I noticed that following a normal cold start, engine idle speed would slow down, and sometimes the engine would die. If I gave it a little gas the engine would return to normal idle, and be fine. It would not happen after warm starts. Shortly thereafter I got the CEL. I bought a code reader, and it told me P0171. I found this forum and I started to do some research. I read the Hayes manual, Mazda repair manual, and some related threads on here. My code reader is one of those cheapies that only reads and erases the codes.

Following the advice from here I cleaned the MAF sensor, no luck with code. Then I used a bottle of fuel injector cleaner, no luck. Finally, I replace the front/first 02 sensor with a Bosch universal. No luck, my reader kept showing the same code and it would not clear.

I took a break from troubleshooting and for the next 2 weeks car ran fine, but cold start/idle problem continued and CEL remained on. Then today after being on the rode for 1+ hrs, car had trouble accelerating. From a stop, I would press the accelerator and it would accelerate very sluggishly. It also seems to accelerate slower at cruise. Then sometimes during an acceleration it would switch gears several times (up and down) or that's what it felt like. It seemed like the engine was not keeping a steady RPM so the transmission was having a hard time picking the right gear.

Took it home and did some more research. I pulled the PCV valve and gave it a shake, it rattled fine. I pulled the plugs (NGK) and they looked fine (I guess?), they had a light brown color on them. I also accidently pulled out the fuel injectors (I thought they were the spark plugs, I am really new at all this) Once I saw and smelled the fuel I decided to disconnect the battery. After I put everything back together and took it for a drive the CEL light was out and the car seemed to run fine, but it had the cold start/idle problem.

Does anyone have any idea what is going on? Why didn't the code reader clear the code? I know why disconnecting the battery cleared the code, but why didn't it come back on? Are the cold start/idle, CEL, and acceleration problems related? Or do I have multiple problems?

Any help would be appreciated, thanks.

[Captain KRM P5]

System Too Lean (Bank 1)

What does that mean?

Basically this means that an oxygen sensor in bank 1 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1.

Note: This DTC is very similar to P0174 (http://www.obd-codes.com/trouble_codes/generic/p0174-system-too-lean-bank-2-oxygen-sensor.php), and in fact your vehicle may show both codes at the same time.

Symptoms

You will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a hesitation/surge on acceleration.

Causes

A code P0171 may mean that one or more of the following has happened:



The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters (K&N, etc.) can cause the MAF to become dirty if the filter is over-oiled
There could be a vacuum leak downstream of the MAF sensor.
Possible Solutions

Possible solutions include:



In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
Inspect all vacuum and PCV hoses, replace if necessary
Check for a dirty fuel filter and proper fuel pressure

[MSdestro]

you have multiple probelms. sell the car adn buy and srt-4

[BlkZoomZoom]

There is an updated Maf sensor you need. I believe they extended the warranty on them so you may get lucky.

[Shane5425]

prolly the maf, but could also be the first o2 sensor, i had warrenty change both of them out...