2019 Mustang GT - P0300 Code

[funks_5.0]

I also just replaced the battery in my car a few months ago. It showed good (12.6V to be exact) with the quick handheld tester at AutoZone. I didn’t trust that, so I requested that they do a load test and when they did, the battery immediately failed, so they replaced it under warranty. I posted pics that I took of the battery on the machine at AutoZone somewhere on M6G, but I can’t seem to find them now.

I was able to take some pictures of the engine bay, the bottom outlet of the intake pipe goes to an inlet right after the throttle body. One of the side ports is capped and the other runs to an inlet on the right valve cover.

Also the MAF model number I have is different which maybe represents the fact that it is the tune required kit, however, I am not sure how to go about confirming this or not.

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[NGOT8R]

Disregard that pic of the part number that I sent you earlier. It’s actually the number for the factory harness that plugs onto the MAF sensor, not the MAF Sensor.

Just for you and the greater good of the M6G community, I pulled my filter and MAF housing from my car to take a pic of the sensor. Here is the exact part number for the no tune required PMAS MAF Sensor. Just pull your filter and MAF housing as well and compare numbers.

 

[NGOT8R]

Were you able to compare the part number on your sensor to mine? If your sensor says FoMoCo on it, then you still have the factory sensor installed into the intake tube. I did some research on this a while back, and the 5.0 cars used the same sensor. If that’s the case, you might need to address things via a tune, especially with the IMRCs being locked out anyways. A call to PMAS will help conform whether you can get away with running the factory sensor in their MAF housing without a tune or if the transfer function needs to be adjusted. Check YT to find videos explaining MAF transfer function.

While you have the MAF housing disconnected from the silicone coupler comparing part numbers, clean it really good with the MAF sensor cleaner as mentioned earlier (see green arrow in pic). Be careful not to touch the element itself.

 

[NGOT8R]

One last observation is, your filter needs to be cleaned. I clean mine in a sink filled with hot water and Dawn dishwashing liquid soap. Let it soak for about 15 min., swish it around and then rinse with a sink sprayer from the inside out as you rotate the filter in your hand to free any remaining trapped dirt that may be caught between the pleats.

 

[funks_5.0]

You should be able to configure the tube different ways if needed. It’s been over 3 1/2 years since I installed mine now and it seems like I might have removed a plug at the bottom and installed the supplied 90 degree fitting with hose barb to attach that hose to. That’s easy enough to check by looking on the bottom of the tube to see if it has a block-off plug. the main thing is to ensure you have no leaks in the system. My PMAS came with multiple fittings and I only used what I needed to, in order to avoid interference with my nitrous solenoids.

I finally had a chance to pull the MAF sensor and it is labeled as FoMoCo with no PMAS logo on it. I can assume this is probably the stock MAF sensor, without a tune on the vehicle I would guess this would cause some issues. Any chance it could cause a random misfire P0300?

 

[NGOT8R]

I finally had a chance to pull the MAF sensor and it is labeled as FoMoCo with no PMAS logo on it. I can assume this is probably the stock MAF sensor, without a tune on the vehicle I would guess this would cause some issues. Any chance it could cause a random misfire P0300?

It’s possible. A dirty sensor and filter can also wreak havoc too. Try cleaning those first and then reevaluate from there. If that doesn’t eliminate the problem, then buy the PMAS MAF sensor that I have. It’s going to be much cheaper than buying a tuning device and paying for a tune which is going to cost somewhere in the range of $800+. However, if you do intend to have the car custom tuned, just keep the FoMoCo sensor in place (still clean it and the filter though), as the tuner can tune with it. My only suggestion then would be to contact PMAS and ask them to email you the Transfer Function info., so you can share that with your tuner before they wrote the tune for you.

 

[funks_5.0]

Ok so I have some updates on this issue. Firstly, the dealership I bought the car from paid for a highly rated performance shop near me to dyno tune the vehicle and get it running right. This was a month or so ago and since then the car has been running great. The check engine light is no longer present and a couple weeks after it was tuned I checked for any DTCs that did not illuminate the CEL and all was good.

However, a couple days ago I experienced the rough idle again which has now lead to 2 stalls of the vehicle again. I can go into more details of the problem but I feel the forum is already swamped with detailed experiences of issues with VCT and my cars issues are matching. Went into forscan and still no DTC's. After some research sounds like my issue could be a VCT problem, I went ahead and took 4 different logs on forscan through different idle/driving conditions. Below is a snip from the log after a short drive, maybe 3-4 minutes of a drive. Got the cylinder head temp up to about 190 and then let it idle. I have another log as well that I can share if someone has some advice or experience with VCT. It does not look like the intake is following the commanded? Could this be what causes my stumble/rough idle and stalling issues? I do not have much experience with this, just trying to learn as I go! If anyone has any advice, thank you in advance!

FYI I have the 4 logs I created in .fsl files that I am willing to share as well if that can help someone get a better look.

 

[funks_5.0]

Ok so I have some updates on this issue. Firstly, the dealership I bought the car from paid for a highly rated performance shop near me to dyno tune the vehicle and get it running right. This was a month or so ago and since then the car has been running great. The check engine light is no longer present and a couple weeks after it was tuned I checked for any DTCs that did not illuminate the CEL and all was good.

However, a couple days ago I experienced the rough idle again which has now lead to 2 stalls of the vehicle again. I can go into more details of the problem but I feel the forum is already swamped with detailed experiences of issues with VCT and my cars issues are matching. Went into forscan and still no DTC's. After some research sounds like my issue could be a VCT problem, I went ahead and took 4 different logs on forscan through different idle/driving conditions. Below is a snip from the log after a short drive, maybe 3-4 minutes of a drive. Got the cylinder head temp up to about 190 and then let it idle. I have another log as well that I can share if someone has some advice or experience with VCT. It does not look like the intake is following the commanded? Could this be what causes my stumble/rough idle and stalling issues? I do not have much experience with this, just trying to learn as I go! If anyone has any advice, thank you in advance!

FYI I have the 4 logs I created in .fsl files that I am willing to share as well if that can help someone get a better look.

Adding on to this, I just put in a new PMAS air filter and cleaned the MAF sensor per suggestions. I feel like the AFR looked a little bit more stable, could just be a coincidence. The car is still struggling with rough idle when its warmed up at a stop light. It is also throwing a P0316 code, no CEL. I am thinking the code could be due to the tune, but as far as the rough idle and stumbling it has not gotten better. Everything points me in the direction of the VCT but if anyone has suggestions on troubleshooting other items that would be great.

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