Nasty misfire with high LTFT, worse at cold start w/ logs

[jonjon]

Year/Make/Model: 2013 Mazdaspeed3
Mileage: ~165000
Location: Phoenix, AZ
Concern: Nasty misfire with a high LTFT
DTC's: P0300, P0303, (inconsistent) P2096
Modifications: CS turbo inlet pipe, race pipe, CS HPFP internals
ECU/Tuning Software: Versatuner
Tuner: N/A
Is the concern intermittent? The LTFT DTC is intermittent but the misfire is constant
Can you duplicate the concern? Yes
Recent Repairs: Changed spark plugs, moved around coils, swapped different wideband O2 sensor, checked for boost and exhaust leaks (none), compression test (~180 across the board),

Hi everyone, my speed recently began to misfire pretty badly. I was sitting on CS HPFP internals and a rebuild kit which I threw into the car to maybe alleviate the problem but there was no change. Prior to the misfires the LTFT was beginning to climb higher and over a several week period. I have taken many data logs where the AFR is ~14.3 but the ECU is still maintain a high LTFT of 10+. I have taken a look at both potentially vacuum leaks and ignition problems but to my eye, I have no leaks and swapping plugs and the coils around did not change the misfire behavior. I did manage to borrow different wideband sensor from someone off my local Facebook group but swapping that in did not change the behavior either. In retrospect, I did forget to unplug the battery during that swap but I did go for a short drive and took logs.

I am currently suspicious of the PRV (I did the test and it only climbed to around 1200psi but my fuel pressure which driving and at idle appear fine), the HPFP spill valve (during the rebuild, it felt as through it was seized to the housing and took an incredible amount of force to remove it from the threaded housing, I only replace the O-ring in accordance to the CS video and did not directly clean the spill valve solenoid(?)), O2 sensors (the AFR doesn't look ideal but maybe the car runs extra rich with the DTCs to protect itself?), MAF (I checked the wiring and cleaned it but maybe its the problem causing the AFR issues?)

I have a bunch of logs that I took but to my unexperienced eye, I have no idea where to take a deeper look. Thanks to anyone willing to take a look at these logs and maybe give me a suggestion at where to maybe start probing to get a better diagnosis.

NOTE: The log with the "new" O2 sensor was started when the car was cold to maybe record anomalous behavior from the car being in open-loop. The mods excluding the CS HPFP internals were on the car for months before the symptoms began.

 

[Enki]

Couple things:
1. Who is the tuner?
2. What are the DTC definitions (don't make others look this up for you)
3. What, if anything, has changed since just before having this issue?
4. What fuel are you running? E mix? Pump gas?
5. What intake do you have? Does it have an airflow straightener?
6. At idle, remove the air filter (or rotate it 90 degrees if cone filter) and see if the trims change
7. Try clamping the evap line and see if the trims change (this is the hose near the HPFP with the inline filter disk; just start the car, start a log and pinch it off to prevent flow through and see if the AFR or trims change when you pinched it). Most likely, if this is the issue, you will hear the engine idle change when you do this if this is the cause.
8. Wiggle the MAF wires at idle and see if the engine sound changes. If it does, you may need to cut out and replace the MAF connector (I needed this on my car).

The logs just look like you either need a mafcal or maybe fixed a vacuum leak that was tuned around previously.

 

[jonjon]

1. No one, if the car is tuned it was before I purchased it (auction), I just assume the tune is stock. The race pipe was on there originally and the CS turbo inlet pipe thrown in because the OEM one had a vacuum leak. I only used Versatuner free for the data logging features.
2. P0300: random misfire, P03003: cylinder 3 misfire, P2096: post catalyst system fuel trim too lean (bank 1)
3. Before the problem, the most recent thing I swapped out was the turbo inlet pipe for the reason above. Initially before and after this change my LTFT was sitting around +5.
4. Pump gas, 91 octane is all we got readily available in Phoenix.
5. Stock air box
6. I will try this in the next day or so
7. I will also try this and create an update here
8. I did attempt this some time ago and wiggling the wires did not change the engine sound but I will try again a little more vigorously

I would be surprised in regards to a mafcal as that part of the intake is completely stock. The screws that hold down the MAF are a little loose but it appears to sit and seal properly

 

[Enki]

With the stock intake, replacing the air filter if it looks dirty would be a good idea. The stock straightener is meh, but the intake itself is so small diameter this shouldn't be the issue (unless the air filter is so heavily dirtied to one side that its causing reading errors at the maf).

Also, the misfires could be because of a lean or rich condition, so it's entirely possible that fixing the fueling/air issue will also fix the misfires.

On second thought, another quick high priority test you should do is to disconnect the hose going from the turbo inlet (cap/plug the inlet port) to the valve cover and see if there is smoke coming out of the valve cover or if it's drawing vacuum.

If smoke is coming out at idle or it's not pulling vacuum, chances are good you've lost some ringlands and that's why the car went to auction, for whatever reason.