Rough Idle / STFT 24+

Hey all, having some issues at idle. I’m attaching a log for reference at idle.

Year/Make/Model: 2007 Mazdaspeed 3
Mileage: 122,xxx
Location: Jacksonville, Florida
Concern: At idle, intermittently the car will lean out, AFR goes wonky and the STFT will go wonky up to 24.8. While driving it seems normal, but at idle it is intermittent. No issues going into boost, or driving, not that’s noticeable anyways.
DTC's: Only codes are pertaining to VTCS and EGR delete
Modifications: BNRs4, JMF manifold, CNT exhaust headers, 3” downpipe/exhaust, JBR Oil catch can VTA (with check valve inline to intake and check valve between VTA filter) DM pcv plate and new pcv valve, all vacuum lines ran to bottom of JMF manifold with new lines, DM 3.5” intake, Tial BOV (new o-ring), serviced fuel injectors from CW turbocharger, Overspeed seals, Bosch 3 Bar, HPFP internals, Cobb 3 port EBCS.
ECU/Tuning Software: Accessport
Tuner: Will @ PD Tuning
Is the concern intermittent? Yes
Can you duplicate the concern? No, only happens at idle, can’t seem to make it happen, happens randomly.
Recent Repairs: smoke test, boost leak test, compression test and cylinder leak down test. No visible smoke or vacuum leaks, boost leak held pressure, compression and cylinder leak down was confirmed good by tuner.
Thermostat, temperature sensor, knock sensor all replaced at 120,xxx miles, VVT from Edge done at 116,xxx miles

I have Rey’s rebuild kit for the fuel pump that I haven’t done just yet. I’m also looking at replacing/cleaning the FPRV if needed. Just don’t want to keep throwing money at things if they’re not needed.


Correction: View attachment datalog3.csv

 

Check the wiring to the MAF for damage, could also be a bad MAF

 

Recently cleaned the MAF, visual inspection of wires seem intact. Further testing suggestions to determine wiring or sensor ?

 

swap with a known good one if you know someone local that has a speed. you could also try to log maf voltage while the issue is happening.

 

The log I posted should have the MAF voltage. That log was taken during said event.

 

If you purchase a MAF make sure you either get an OEM or a Denso MAF. These motors tend not to play well with el cheapo MAF sensors.

Rock Auto has Denso MAFs and Denso was the OEM manufacturer for Mazda.