Stubborn, persistant CEL. P2177 & P2179

[meangreen01]

I've been battling these codes persistently for some time now on my Mazda6 V6(essentially a Ford Duratec 30 with VVT). The codes mean lean conditions bank 1 and 2 respectively. It's always the same codes, but sometimes only the 2179(bank 2). At first they would appear every few months, but gradually have gotten much more frequent and appear every few days now. The car seems to drive fine otherwise. Maybe a little sluggish, which could be attributed to the change back to stock airbox, but idle is smooth, doesn't stumble during acceleration, etc.

About the intake. I had an aftermarket cold air intake on it that I had attributed the codes to at first, and since the CEL's were infrequent, I just cleared them with my scantool and went on my merry way. When they gradually became so frequent that they were becoming a PITA, I removed the CAI and put the stock airbox and filter back on. But, the codes are still there and are basically constant.

After finally learning some of the more advanced features of my scantool and studying the Mazda factory service manual, I'm leaning toward the opinion my MAF is bad. The freeze frame at the time of CEL showed my fuel trim high(~+20) and the MAF signalling way too much air entering engine(nearly 2 lbs/min at 1500 rpm). Unfortunately, my scantool doesn't read the MAF voltage so I have to go by airflow mass readings, which, according to the manual are high for a RPM essentially just off idle.

Just wondering if any of the experts out there could kindly offer their opinion.

 

[4x4chevydude]

It could be the MAF sensor, was it an oiled filter on the aftermarket intake? If so try cleaning the MAF and see if that does the job, otherwise it could be a gasket leak somewhere letting air in intake, Exhaust ETC.

 

[meangreen01]

No it was a dry filter. I also tried cleaning the MAF with CRC electronics cleaner. Also, I sprayed around the intake and surrounding hoses using carb cleaner to see if there was a surge in RPM- nothing. Thanks for chiming in.

 

[punisher]

Since you have a scantool:

Rich trims at idle, lean on accel/engine load= MAF.
Rich trims at idle, trending normal on engine load= stuck fuel regulator/bad pressure sensor in a returnless sytem.
Lean trims at idle trending to normal with engine loaded= vac leak.

When MAF/Vac leaks first occur, when the problem is minor, you will often get a lean code on just one side. O2 sensors are never the same, and with multiple banks, one always runs slightly leaner than the other. Nature of the beast. When you start to go lean, the weaker/slower switching O2 will code first (even if it is in spec).

 

[meangreen01]

Bringing this thread back from the dead just to update. I replaced the MAF sensor and all is well. It's now been 3 months and about 3k miles so I'm pretty sure I've got it licked finally. The MAF I put in was a brand new(not reman) Borg-Warner.

Now I'm questioning what exactly caused the failure. The sequence of events surrounding the issue are:

(1) I installed a Mazdaspeed CAI. The installation dictates that the MAF be moved out of the engine compartment down into the fenderwell, where it's subject to water, dirt, etc.

(2) A short time later we got caught in a torrential downpour and the car started acting loopy and shortly thereafter wouldn't start. Brought it the dealer as it was still under warranty. Dealer said the MAF got wet because of the CAI and denied fixing it under warranty even after I pointed out I was using THEIR performance part. I refused to pay their inflated repair quote and got a reman from AAP.

(3) Car drove fine for a few years and then the CELs began popping up leading to the creation of this thread.

I find myself wondering if the CAI is to blame or the AAP reman MAF? OR, possibly a combination of the two? A marginal part exposed to a harsher environment perhaps?

The Wife drives the car the most and she misses the growl and extra oomph. I do too as it did make a difference. I don't know if I put it back on if it's going to mean replacing the MAF every few years or what. Aren't MAFs designed to be water resistant? What about the thousands that get wet when the engine gets washed?

Input or suggestions welcomed.

 

[The_Eric]

I will say that the re-man (likely a Cardone of some kind) is definitely suspect. We've installed Cardone MAF's that have been WORSE than what we took off!

Like you said, usually the sensors are pretty well sealed up, but maybe you can seal it a little better for use with the CAI. Use some dielectric grease at the connector and some silicone along the seem and on top of the screw heads (if applicable). If the filter element is in a spot where it could be exposed to water, then I'd add some sort of pre-filter to it to help knock down any splashes before they can get into the air stream and mess with the hot wire filament.

 

[eljefino]

Advance/Cardone MAFs are terrible. I'd rather get a junkyard one. The cores get turned in because they're flaky, they get bench tested okay, but something in the electronics goes wonky when driving/vibrating/warmed up. Turn in as a core, get tested good, repeat.