Who has changed out an O2 sensor?

[Gmac03]

Help Troubleshooting Surging Engine

Car is running funny when you're on the throttle. Power comes in waves, seems like the computer is steping in and holding the power back so it comes on intermittently.

Brought the vehicle to the dealership and they said it was a bad O2 sensor. But then they told me at 38k it's out of warranty and I didn't want them to fix it for the quoted 400+ dollars. So I had them order the part and plan on fixing it myself.

Now the part won't be in until Monday, so I don't know for sure if it's the front or rear until then. Which leads me to the most important question...Who has changed out their O2 sensor and how much of a PITA is it?

Looking quickly under the hood I can see the front sensor in the top of the manifold, doesn't look like I'd have to do anything out of the ordinary other then unscrew and unplug and swap it out. Now looking at my FSM it's showing the rear sensor to be under the manifold and the FSM says to remove the battery box, intercooler and manifod to get to it. Does it have to be that difficult our can you access it from underneath?

Thanks for the help. Also searched a ton, couldn't seem to find a How To or much on this subject for our cars.

Thanks.

Gmac

 

[GoFast]

JUST FINISHED mine an hour ago....

The hardest part in all honesty is getting those(two) damn connectors apart. The harness is on the drivers side almost directly under the battery tray. The higher you can get the car, the better.

To make sure it IS your o2 sensor, disconnect those clips and take it for a spin. See if the problem goes away. If it does then replace it.

Getting the o2 sensor out wasn't that bad. Spray a little pb blaster when you start the project. While that is soaking in, take your intercooler off and get that little heat shield on the firewall off. You should now have plenty of room. Break the o2 sensor loose, spray a little more PB blaster on there, and work the threads back and forth a few times. Then just take it out.

Putting it in is even easier and the steps are basically the same, just reversed. You could forgo the PB blaster on the install though (lol2)

Total start to finish time, a little over an hour.

 

[Gmac03]

Thanks for the nod of confidence. In you're post which sensor are you referring to? The front/rear or both?

Thanks.

Gmac

 

[GoFast]

The front.

 

[Gmac03]

Thanks.

Gmac

 

[carbosam]

they are changing mine this week

 

[Gmac03]

they are changing mine this week

Yeah and they would of been changing mine, but at 400+ dollars, I just can't stomach that.

How many miles do you have the on car and what did they quote you? Unless it falls under your warranty.

Gmac

 

[carbosam]

Yeah and they would of been changing mine, but at 400+ dollars, I just can't stomach that.

How many miles do you have the on car and what did they quote you? Unless it falls under your warranty.

Gmac

its under warranty and my car has 34k kilometers...so about 20k miles i guess

 

[Gmac03]

Very nice...I'm 2k over the warranty so no bueno.

Gmac

 

[Gmac03]

UPDATE:

Just picked up the part around noon, went to eat lunch then started working on the O2 sensor. Brought it buy a buddies shop cause he had much nicer tools, took about 30 minutes tops.

Now the bad news is that the O2 sensor didn't fix the surging throttle that I get in higher gears. So brought it back to the local mazda dealership and they said "well that was just our starting point". Wow! I'll hold off all further comments and judgements until the situation is resolved and I've made an appointment for them to see my car again come this Friday.

So here is the timeline so far.

Thurs, 3/4/10, brought the car in, they said it was an O2 sensor, didn't have it in stock would over night one.

Tues, 3/9/10, O2 sensor arrives, I go pick it up and install it an hour later. Problem still exists, they tell me that "was just a starting point." So I make another appointment for this Friday.

To Be Continued...

Gmac

 

[GoFast]

That blows. This is why I said to disconnect it the old one and take it for a spin first. Had you done this and the problem went away, then you could have bet a new one would have fixed the issue. If you disconnected it and it DIDN'T make the problem go away, you would know the o2 sensor was NOT the problem and you could have returned it and saved yourself $380.

UPDATE:

Just picked up the part around noon, went to eat lunch then started working on the O2 sensor. Brought it buy a buddies shop cause he had much nicer tools, took about 30 minutes tops.

Now the bad news is that the O2 sensor didn't fix the surging throttle that I get in higher gears. So brought it back to the local mazda dealership and they said "well that was just our starting point". Wow! I'll hold off all further comments and judgements until the situation is resolved and I've made an appointment for them to see my car again come this Friday.

So here is the timeline so far.

Thurs, 3/4/10, brought the car in, they said it was an O2 sensor, didn't have it in stock would over night one.

Tues, 3/9/10, O2 sensor arrives, I go pick it up and install it an hour later. Problem still exists, they tell me that "was just a starting point." So I make another appointment for this Friday.

To Be Continued...

Gmac

 

[GoFast]

Also, was there any CELs??

 

[Gmac03]

No CEL's. And me and my $380 agree with you.

Gmac

 

[GoFast]

No CEL's. And me and my $380 agree with you.

Gmac

Ugh...they really shouldn't have suggested the o2 without a CEL....

 

[Gmac03]

That's what I think, but I'm not the one with the diagnostic tools. I would assume they could see something that I can't, seeing that this is strictly computer based and not mechanical.

Looking at my FSM it says that surging can be caused from Improper Engine Compression, Imprope Valve Timing, or Fuel Quality. Now that's just per the trouble shooting section, I could understand if my plugs were toast, but the surging wouldn't be rythmic, I would think. Improper valve timing? Sure but I would assume it's one of the sensors kicking in with a bad reading that would be retarding/advancing the timing and then with quality of fuel, I've never used anything but 93 octane it's entire life.

So my guess is the MAF sensor or the rear O2 sensor, but I don't think the rear O2 sensor has much of a job. A long shot could be the fuel pump, but what do I know. I'm no mechanic, that's why I brought it to the mechanics.

Gmac

 

[Super Unique]

My past experience with mazda repairs are in line with what your going through now. It makes me happy that I purchased that top of the line extended warranty

I pay $100 and stand back and let them all duke it out, so far I have saved over $1500 out of pocket, and that was just my first problem, which paid for the warranty. (shrug)

 

[Gmac03]

Update:

UPDATE:

Brought it back to Mazda again. They had it for the greater part of the day and in the end told me they couldn't find what was wrong with it.

They said they called Corporate Mazda and they told them to take all of the aftermarket parts off of it.

So my dealership called me and said to take off the aftermarket intake and BOV. Told them that the "aftermarket intake" is your mazdaspeed CAI that you installed and yes I can swap out the forge BPV for the stock mazda one. They also didn't want to do the work because then they would have to charge me for labor.

So...they don't know where to go with it. But are now pointing the finger at the CAI.

Now if it was the CAI and the MAF, wouldn't that throw a code or could it just drive like crap?


Gmac

 

[MSMS3]

They are stabbing in the frigging dark!

Are they going to give you your $380 back for a part they said you needed that was purchased on their advice for an O2 sensor that was not defective?

Now they want you to take off an MSCAI that they manufactured and go to the trouble to reinstall the stock air box so they can tell you that the CAI is not the problem?

Yes, take off the Forge and reinstall the stock BPV. That will be easy and you can see if that solves your problem. Maybe you just have your Forge adjusted incorrectly?

 

[Gmac03]

They are stabbing in the frigging dark!

Are they going to give you your $380 back for a part they said you needed that was purchased on their advice for an O2 sensor that was not defective?

Now they want you to take off an MSCAI that they manufactured and go to the trouble to reinstall the stock air box so they can tell you that the CAI is not the problem?

Yes, take off the Forge and reinstall the stock BPV. That will be easy and you can see if that solves your problem. Maybe you just have your Forge adjusted incorrectly?

Will definately swap out the BPV, too easy, but it's not the problem. I don't see how the BPV could be creating the symptoms the car has. Now it is possibly the CAI, due to the MAF, but you would think that would either throw a code or be experienced in all of the gears.


Here is some additional troubleshooting for anybody that wants to take a stab at it.

If I'm WOT in 3rd gear and continue to row through the gears up to 6th, I have no surging. If I go WOT starting in 4th, 5th, or 6th, I have surging.

Can't figure this out for the life of me. Hopefully I'll have time to drive with a buddy this week and he can put it on his diagnostic machine and watch the MAF values to rule that out of the equation.

Gmac

 

[Super Unique]

has anyone confirmed that there are no issues with your purge valve?

This is a very common fault that causes problems with incorrect air metering.