Check Engine Light - O2 Sensor?!?
 

2000 Protege LX. Hopefully someone can help - my check engine light is on and after paying for a $75 engine analysis, the computer came up with a bad O2 sensor. I'm currently running too lean - I figured it was the O2 sensors as well. Turns out that O2 sensors are $480; but I bought two universal sensors for $70/ea. After installing them, the problem did not go away. The engine light is still on and the car is running too lean.

Has anyone had this problem?

Symptoms: Loss of power in high RPM, decreased acceleration, jerks with the pedal is to the floor. I also replaced the fuel injector around 40,000 mi ago.

First off, never pay for a computer scan!! Most autopart stores will scan your car for free. Was the computer cleared after installing the new O2's? With the pedal to the floor, you car goes into a preprogrammed fuel map, and disregards the sensors anyway, so that sounds a little strange.

The second O2 sensor does little as far as A/F is concerned. It mainly checks to see if the cats are working properly. Also, when the scan was done, the code would have specified which O2 sensor was tripping the code.

When a CEL comes on and the code brings up a sensor, it DOES NOT always mean that the sensor is bad. Usually, it means that sensor is giving a reading that is out of range. In this case, if it says you're too lean, then you're probably running too lean. Things that can cause a lean condition: bad injector(s), low fuel pressure (fuel pressure regulator or fuel pump), faulty Mass Air Flow sensor, faulty Throttle Position Sensor, and faulty Intake Air Sensor.

Where to start? You can test each component separately and ensure they are operating within the their limits. A multimeter comes in handy for this. Testing can be a tedious process. . . this is why shops charge so much.

In this case, it might be better to have a shop look at it, rather than throwing parts at it until its fixed. Funny thing is I used to cringe everytime someone replied with a statement like that. Mainly because I like to do the majority of the work on my car and HATE paying outrageous shop fees.

Thx
 

I did use AutoZone's free analysis - their computer reported the "too lean" error. I then went to a shop twice, $75 a pop, which reported the O2 sensor error, before and after the new installs.

I'll probably take the car back in - but the garage wants to perform another analysis at $75 before working on the car.

Anyway, I appreciate the help and will post the problem and cheap solution if they ever figure it out!

It sounds like the shop you've been going to is using the "throw parts at it until it's fixed" method. Sorry to hear of your troubles. That just pisses me off!!! No way should you have to pay another $75. Did they replace the sensors? If so, they misdiagnosed the car and replaced unnecessary parts. . . they need to fix it right!

Also, did they clear the code and then the light came back on? The code has to be cleared from the system. It doesn't reset just by retrieving the code.

If you can get your hands on a shop manual, there are trouble shooting charts. This would accelerate the solution process.

I know GNO! I told them if they want my business to waive the engine analysis fee.

My friend, who has one of the fastest Neons I've seen, and myself installed the O2 sensors. Again, this shop wanted to charge $480 per sensor and $100 labor. I was not going to spend a total of $1060 for two little parts + install ... so, I spent $140 and 40 mins.

That's why I went to the Protege Board with this problem - I'm afraid of a misdiagnosis and constant money spending. I'm still looking for another "HONEST" shop to work on the car. I told want to take it to the dealership because of cost and and mods I made. But, that might be the best thing to do.

If you have a 1.6 check with the dealer to see if you car is under the special service program for the mass airflow meter . I would guess the code you had was P0171 - bank one system too lean. Am I warm?

cel
 

w
as the code a po171 system lean ? if it is you need a maf sensor
as mazda has a problem with this yr.

little bit late there buddy, and a bit repetitive......:)

PO171 error is correct
 

Yes ...

You are correct - PO171 "too lean" error - I ended up losing my job several weeks ago - no money to fix - so, I driving with the error - for now. Wish me luck - I might have some tricks up my sleave.

You know my CEL came on with a "too lean" condition and it was a damn vacuum line. So check everything.

I thought it was the vacuum line as well - but it wasn't.

I had the exact same error code read at autozone. I just wiped off the maf with a Q-tip and rubbing alcohol. Reset the computer and everything has been fine. No money fix really.