Throttle body/rough idle lean issues

StevieWonder711

Greenie N00B Member
Year/Make/Model: 2007 Mazdaspeed 3
Mileage: 161,000
Location: Missouri
Concern: Car idles rough, TB doesn't open
DTC's: In the pic
Modifications: bone stock
ECU/Tuning Software: Versatuner
Tuner: Stock tune
Is the concern intermittent? No
Can you duplicate the concern? Yes
Recent Repairs: Cleaned Maf sensor, valve cover gasket, oil change, trans fluid change, new front axle
Correction:


Some back story: I bought this car on marketplace and it drove good back to my place over an hour away. Used versatuner to see how exactly engine was running and had erratic AFRs (29+ or 8) but it seemed to drive and idle ok. STFT were always at +25%. I cleaned the maf to see if that helped the AFRs and car idled worse. I couldn't rev above 2k rpms and got all the DTC codes (attached in pic).

The flapper of the throttle body wouldn't move when I had the battery on, do these codes suggest I just need a new throttle body or are the computer components fucked up?
 

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  • 10-4-2024CEL.png
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Based purely off of what you've said, a throttle body sounds likely. Sometimes DTCs are sent erroneously because of other problems (e.g. crank position/cam position codes can be sent if the engine is just running like absolute shit, I've seen it happen with a bad pressure relief valve).

Upload a datalog, it'll help a lot more than trying to nail things down based on word of mouth. Just log while it idles (or attempts to).

IAT codes point to your MAF, as intake air temperatures are measured at the MAF sensor.
P0123, P0222, P0638 and P2107 all seem TB related.
P2187 is just fueling/air intake imbalance.
P2246 means that your O2 sensor is either broken or unplugged or something in that regard.

"Circuit high" means that it's reading maximum voltage at the given circuit, maximum voltage signals a break (typically 12v when car related). You've definitely got a project on your hands.

First thing I'd do is get a new O2 sensor (or diagnose the O2 sensor problem rather). The O2 sensor tells the ECU what AFR it should be targeting with its fuel trims. If you've got a bad O2 sensor, it'll affect almost everything about how the engine runs.
 
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Since it got worse after fooling with the MAF I would check there

Look for any tears on the oring and make sure that the wiring is all firmly seated in the connectors and not corroded
 
Maf o-ring looks good and the connectors look good. Car idles way worse with maf disconnected if that rules anything out

I can't get a log of the maf right now since my buddy has the obd2 port, but I found a log of me driving around before the throttle/rough idle.
 

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Update: I installed a NTK upstream o2, got a different maf sensor from a turbo cx-7 (looked to be in better condition than mine) and replaced the throttle body on my car with one from the same turbo cx-7. The idle is very consistent now and AFR reads at a consistent 14.5. my STFT are also no longer stuck at +25%. I only have one CEL now, p0638 Throttle Actuator Control Range/Performance. It seems I still have no throttle response, whenever I try revving, the rpms hang at about 1800 and drop slowly down to idle.

Here's a log of the idle and revving. Idle is significantly better now but rpms won't go above 2k
 

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