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I know this issue has plagued many people, and in many different ways... So I figured I'd share my experiences.

2006 Mazda3 S (2.3L) hatchback, Federal emissions. Mfg 03/06. 100% stock (no CAI or any of that nonsense).

Let's go back about 8 months. CEL came on at around 120,000 miles, yielding a P2177 code (System Too Lean Off Idle Bank 1). No discernible issues beyond the code. I'd reset it either via a scanner or by disconnecting the battery, only to have it return anywhere from 60 to 150 miles later.

Within the first month, I began having odd cold start issues in which the engine speed would "bounce" (or surge) every ~2 seconds or so, feeling like it was nearly stalling between each burst. After about 15 seconds, the idle would smooth out after exiting open loop mode (the same point in time when engine speed would kick down/even out prior to the issue starting).

I replaced my air filter, cleaned my MAF (center of the issue, more on this later), and eventually replaced my purge solenoid valve since that was a common reported cause of the issue. No change in behavior.

After about another month, I bought a proper OEM NTK wideband O2 sensor and installed it (jeeeeeeesus, what a pain - be *EXTREMELY* careful not to strip the exhaust manifold threads when doing this). Once again, no change in behavior.

A couple months later, the issue worsened... Cold starts remained awful and surged as before, but now I started losing power across the entire powerband (especially at 4,500+ RPM in 4th gear, which made passing on the highway impossible). The issue felt a hell of a lot like fuel starvation, as I'd dealt with it before in an old 1988 Mercedes 300E (in which the high-pressure pump failed), so I began looking into replacement fuel filters and pump assemblies (since it's internal)... Given the price tag, I decided to put this off.

By this point, I acquired the assistance of a local Mazda dealership service tech, as I'd helped his wife with some math tutoring in preparation for a teaching certification. I explained what I'd done thus far, and he jumped in and started doing deeper dive diagnostics over the course of a few weeks. We did a compression test (perfect), checked the charcoal canister (bone dry), did a live fuel pressure test with the gauge strapped to the windshield, opened up the purge line and blew it out to verify no debris was present (totally clean), and still no change. By this point he was confident that the brand-new OEM purge solenoid valve had failed (as he'd seen it twice before amongst the hundreds of vehicles he'd serviced), so I bought another new one.

Once again, no change.

Freeze frame data indicated that the P2177 condition was happening at around 4,000 RPM, which he found particularly strange. Otherwise, no metrics appeared to be awry and the car seemed generally healthy. He suggested that it could've been a problem with the VVT sprocket (the pin hardening issue for which there was a TSB) or with the VVT actuator valve, but that it'd be best for me to take it into the shop so he could use the full spread of diagnostic tools and the knowledge of other techs to help rather than continue with the driveway diagnostics.

Fast forward to a few nights ago... I decided to look up other MAF-related symptoms just because I couldn't shake the feeling that it was still the culprit, and found a thread about a similar-year Mazda6 2.3L that was exhibiting *exactly* the same issues (but with several additional codes). Hedging my bets, I called the dealership parts counter 10 minutes before they closed to wholesale check pricing on the MAF, and went ahead and ordered it since they'd have it by 9 AM the following day.

I then decided to look up a MAF cleaning how-to specific to the Mazda 2.3's MAF, and realized I'd made a grave error.

I had cleaned the IAT (intake temp sensor/thermistor). Not the MAF itself. Both sensors are in the same assembly.

By this point it was 11 PM, so I went to bed and then went straight to AutoZone at 7:30 AM to buy a can of CRC MAF cleaner before work. Popped the MAF out, cleaned the ever-loving snot out of the MAF itself (way down in the tube, *not* the immediately-visible IAT thermistor that I had cleaned before), and left it out to dry.

About 20 minutes later, I threw it back in and started the car (which had not been started in about a week due to my aggravation - I was already shopping for a new car by this point as I was convinced I had a lemon).

Perfectly normal start, no surging/bouncing idle.

I warmed it up slowly and got onto the freeway, and holy [email protected]#$. Power was 100% restored, and even seemed to be better than when I'd first bought the car a few years ago... But then again, this could've been due to the fact that it'd been crippled for so damn long.

It's been 200 miles and the CEL has not returned. Power is still remarkably improved, as is fuel economy.

Long of the short: clean your MAF sensor, not the IAT. I wasted $500+ and several hours of someone's time (not including my own) over something I should've done correctly in the first place.

Just figured I'd share. Now I just need to replace my AC compressor clutch that failed last week and I think I'll be happy to get a few more years out of this thing.
 

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oh.. Yeah. I always make it a point to mention whenever someone says "spray the MAF" I have literally always popped in to mention "make sure you're cleaning the MAF properly, because not many people know how to!"

it happens.
 

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Five years later I was having the same issue with a second hand Mazda 3 I had just bought. O2 sensor was replaced but P2177 code kept popping up after 100 miles. Clean out the MAF and I was able to pass smog.
 
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