P0300, P0171, Driveability issues under heavy throttle

Year/Make/Model: 2011 Mazdaspeed3
Mileage: 94k
Location: GA
Concern: CEL, Stutter under heavy acceleration
DTC's: p0302 and p0171
Modifications: DM mounts (All 3), resonator and muffler delete
ECU/Tuning Software: none
Tuner: n/a
Is the concern intermittent? no
Can you duplicate the concern? yes
Recent Repairs: none
Correction:

Hey all, new to the MS3 community and to this forum. I recently purchased this vehicle. All modifications had been done by one of the previous owners. I am unaware of any other modifications to the vehicle beyond what I can see. Bought the vehicle knowing it had a CEL for a thermostat. Code cleared on the drive from Alabama to Georgia and did not reset. Now I have the codes p0302 and p0171 setting. I am also unable to heavily accelerate (WOT and over 4k rpm) without what feels like it misfiring. If I drive it normal I do not have any other issues besides the CEL. I have been doing some research on multiple forums but mostly this one. I have some ideas but I don't want to just throw parts at it. I would love to be able to share data logs of what is going on but I am very new to data logging and tuning in general. How should I go about this? What is the best way for me to go about recording the data? Should I go with an AP or a laptop and tuning software? Any advice on the situation is greatly appreciated!

 

Have you checked your spark plug gap (.026-.028)? Also make sure you are running the right type.

 

Check the spark plug gaps before you do anything else

 

I will check the spark plug gap tomorrow when I’m at work and I will report my findings. I also have some brand new ngks that I’ll double check the gap on and install.

 

+1 for plugs / gap, never hurts to check the ground near the hpfp while you're there and clean that maf sensor either. Have you inspected your intake to intake manifold for any loose connections / leaks?

Do you have a Bluetooth OBD2 scanner or something? Ltft if you can see them should ideally be within +/-5 up to +/-7 of bigger than that you certainly have a leak

 

I checked the gap on the old spark plugs. All were between .024 and .025. I replaced them with the NGKs. The gap on the new plugs is between .026 and .028. I looked all of the coils over. No signs of damage or corrosion. I cleaned the HPFP ground. I'm assuming that was the ground on top of the HPFP and next to the cam pos. sensor? And I did also clean my MAF sensor. I double checked all of my intake connections. All of them check out fine. I do have access to a snap on scanner. My ltft is between +16-17 at idle. When I was looking at the data list, I noticed that my downstream O2 sensor was reading 0.00v at all times. Maybe that's nothing but I thought they were supposed to fluctuate in voltage. What do you all think?

 

Can you read AFR while your scanner is hooked up and give it some blips? AFR should be fluctuating, if the O2 sensor is bunk it won't budge. Should read lean on decel (>14.7), rich on accel(<14.7).

 

Just checked the AFR. It appeared to fluctuate although the scan tool used 1 in place of 14.7. On accel it read under 1 (around .87) and on decel it read over 1 (around 1.9.) I believe that matches what you were saying @jdab555

 

So here’s a little update after my 40 min drive home. My downstream o2 sensor woke up at some point and started reading. I didn’t notice that until I pulled in my driveway though. LTFT is still reading over +14 at all times. No CEL although I do anticipate it coming back on with the fuel trim reading that high. I did get to do some heavy acceleration and it only acted up once. Which is an improvement but I don’t think my issue is entirely resolved. I’m used to working on chevys and I’m used to much more information being available to me than this snap on scanner can give me. I can’t even view fuel rail pressure or misfire data with it. Anyway, if anyone has more input or ideas I would greatly appreciate it! Thanks!

 

Take a vacuum cap and plug off your purge solenoid at idle. If your fuel trims corrects then your purge solenoid could be leaking vacuum into the fuel tank when the solenoid is closed.

Another thing to check is all your vacuum lines or caps around the turbo, intake manifold etc. Any positive fuel trim can indicate a vacuum leak.

 

I verified the purge solenoid was commanded to 0% and removed the line from the purge solenoid to the fuel tank. The purge solenoid does not appear to be leaking. Although it appears to be running lean the p0171 has not reset yet. I don't hear or see any vacuum leaks and I've been to every spot I can think of with some throttle body cleaner.
I do still have a p0302 though. I did a compression test and a cylinder leakage test today thinking that I may have had a sticking or burned valve. Compression was great all across and so was my cylinder leakage. I'm adding some fuel system cleaner to the the tank today when I fill up. I'm wondering if I have a dirty injector seeing as the misfire is only on cylinder #2 and its intermittent at that. Some may call this wishful thinking. Ill continue to look into any advice or thoughts given and will post my results as I find them!

 

Swap coil packs and plugs and see if the misfire follows.

If the misfire sits on Cylinder #2 regardless of spark plug / coil pack swapping, then I would lean towards taking a closer look at that injector and going for a new cleaned set. You should do a walnut blast too while you're in there, and inspect the harness for any breaks as best you can.

Baby steps!

 

Does any happen to know what compression is supposed to be for the 2.3l? I have access to alldata and they say it should be between 130psi and 186psi and the greatest difference in cylinders allowed is 28.4 psi. I just want to make sure that is correct. I believe my issue is in fact low compression if the specs above are correct. Compression on cylinder #1 - 140 psi, #2 - 135 psi, #3 - 145 psi, #4 - 140 psi.

Also as an update, I had started removing the intake manifold to get a look at the injectors and seals. I think I might need to expand my parts list..

 

I believe spec is 180 when warmed up, with no greater than 10% variance across cylinders being the goal. Your numbers look good, cold compression test?

 

I drove the car into work and only let it set for about an hour or two before doing the compression test. So the engine wasn't entirely cold.

 

I would just like to post an update. I replaced #2 injector, all injector seals, and the intake manifold gasket. I went with graveyard performance for the railside and the upgraded corksport injector seals for the head side. I've been driving it for about 2 weeks now and the CEL has remained off the entire time. I'm thinking my intake manifold gasket was the culprit for all of my problems. The thing just flaked apart. My LTFT is MUCH lower now and my car runs great! So thanks to everyone for your assistance!