MSP is running lean.

[davygravyt]

Hello all.

I bought my MSP from a dealer back in June with 77,000 miles. The previous owner put an injen CAI and stainless IC piping in it. The IC may also be aftermarket, but it's hard to tell with it being side mounted and all. It now has 82,000 miles.

A couple months ago, the check engine light came on, throwing codes for MAF sensor and 02 sensor, and the car developed a rough idle and some hesitation under acceleration. I replaced the MAF sensor, which helped slightly, but the problems persist, and the check engine light is still on. I had my mechanic check it out yesterday when he was replacing my timing belt, and he said it's still throwing an 02 sensor code, and that it is running lean. He blames the aftermarket parts throwing off the A/F ratio. To the best of my knowledge, he checked for vaccum leaks. I'm not sure if he checked the plugs/wires or not.

Any idea what could be causing it to run lean?

 

[davygravyt]

Oh, also, I forgot to mention that my other mechanic mentioned that my turbo may be leaking, because he saw some oil on it.

 

[tweety2300]

Try changing the o2 sensor...

 

[protege3690]

And do u have a boost gauge? Wideband? Those would be your smartest investments right now to help moniter your engine

 

[JDMazdaFamilia]

I would double check with him to make sure he checked for vacuum leaks. My car threw an o2 code and a lean code when I had a vacuum leak, fixed the leak and all codes went away. Sometimes just randomly replacing things that "could" be wrong is more costly than taking the time to find the root of the problem than just guessing and checking. That being said there's no way a cai intercooler pipes and even an intercooler upgrade will make you run lean

 

[davygravyt]

I would double check with him to make sure he checked for vacuum leaks. My car threw an o2 code and a lean code when I had a vacuum leak, fixed the leak and all codes went away. Sometimes just randomly replacing things that "could" be wrong is more costly than taking the time to find the root of the problem than just guessing and checking. That being said there's no way a cai intercooler pipes and even an intercooler upgrade will make you run lean

That's what I thought. Should I check plugs and wires while I'm at it?

 

[Spiced MSP]

meh..IC pipes are possible areas for leaks if the couplers aren't tight all the way, especially before the MAF

 

[mxjosh82]

Does it still have a bypass valve? If it has a BOV instead, is your MAF relocated?

Agree with JDMazdafamilia...No way its running lean with only those mods and sock tune, that tune is pig rich.

 

[CHIQLES]

I agree with everyone.
check couplers, if its the stock side mount check for cracks in the plastic
if it has the bp/bov after the maf it may be causing you issues.
Check for cracked air lines.
Blow threw the air line in the waste gate it should not leak, then suck air threw it you shouldnt be able to either. Thats all I can think. For easy stuff to check shouldnt take more then 20 minutes and use a good flash light..good luck

 

[JDMazdaFamilia]

keep in mind that any cracks gaps or loose ends AFTER the maf sensor will make you go lean every single time. I would inspect intercooler pipes from the turbo all the way to the throttlebody, make sure everything is on there nice and tight. Once you got that down then move onto vacuum lines. Vacuum lines that are unplugged or cracked will also draw in air into the engine that wasn't accounted for by the maf and again, make you run lean. If you have a maf code I also suggest testing the maf. to do this you will need a voltmeter. You will need to probe onto the back of the clip middle wire that goes to the maf, you should have a certain voltage number to that middle (signal output) wire that goes up with acceleration. I have access to all data and can get you the maf specs if you need it. Or if you have a really good obd scanner like the snap on ones, itll tell you the maf voltage. Hope you find the problem

 

[davygravyt]

keep in mind that any cracks gaps or loose ends AFTER the maf sensor will make you go lean every single time. I would inspect intercooler pipes from the turbo all the way to the throttlebody, make sure everything is on there nice and tight. Once you got that down then move onto vacuum lines. Vacuum lines that are unplugged or cracked will also draw in air into the engine that wasn't accounted for by the maf and again, make you run lean. If you have a maf code I also suggest testing the maf. to do this you will need a voltmeter. You will need to probe onto the back of the clip middle wire that goes to the maf, you should have a certain voltage number to that middle (signal output) wire that goes up with acceleration. I have access to all data and can get you the maf specs if you need it. Or if you have a really good obd scanner like the snap on ones, itll tell you the maf voltage. Hope you find the problem

I actually replaced the MAF, and that code went away. The o2 code is the only one it's throwing now.

Also, I'm somewhat new to turbo cars, but I believe it stil has the stock BPV, because it still makes the trademark turkey call when pressure releases (correct me if I'm wrong in assuming it's the BPV that causes this).

I will go over it with my mechanic and check for leaks or cracks.

 

[JDMazdaFamilia]

Turkey can be produced even if you don't have the stock bpv. It all depends on how strong your vacuum source to the bpv is and how hard the spring is on it.

 

[hornsfan10609]

Don't forget to pull the heatshield off the exhaust manifold and check for cracks and missing hardware.

 

[Installshield 2]

they run pig rich in open loop...but extremely lean in closed...but agreed, its not the mods that are the problem and causing the cel...other than their installation possibly...air/vacuum leak somewhere is my bet...

 

[highflyin285]

My car is also running lean after I did a pcv delete with a catch can set up. I'm almost 100% sure I don't have a vacuum leak everything is brand new after the recent full build. I'm looking for any ideas.