Bought 15 GT with two codes p0300 and p0442.

[krazer]

Hello All,

I bought a 2015 Mustang GT with a 18 manifold swap, BBK LTH, GT350 CAI, and with codes p0300 and p0442. The previous owner said it was the o2 sensors that were causing it. Does this sound right? Or should I start trying to chase a small evap leak?

Car seems to drive fine. Anyone could provide a shop in the tampa area (or anywhere in FL honestly) that could help troubleshoot this? Or would a tuner be better to see?

Anyone have any suggestions, on how to diagnose on my end with limited mechanical knowledge?

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[sk47]

Hello; I get a evap code every couple lf years on my pickup. So far I have "fixed" it by working on the seal of the gas cap. At first I would replace the cap but lately have just replaced to O ring or just cleaned it and slathered on some Vaseline. Have to delete the codes with a scan tool or simply disconnect the negative battery cable for a while.

No clue on the other code. If it is due to O2 sensors they can be a DIY job with the correct tools. I would check the wires and connectors feeding the O2 sensors.
Good luck

 

[krazer]

Hello; I get a evap code every couple lf years on my pickup. So far I have "fixed" it by working on the seal of the gas cap. At first I would replace the cap but lately have just replaced to O ring or just cleaned it and slathered on some Vaseline. Have to delete the codes with a scan tool or simply disconnect the negative battery cable for a while.

No clue on the other code. If it is due to O2 sensors they can be a DIY job with the correct tools. I would check the wires and connectors feeding the O2 sensors.
Good luck

Thanks so much for the feedback! Going to try the gas cap!

 

[sk47]

Thanks so much for the feedback! Going to try the gas cap!

Hello; Your car has some purge valves and charcoal cannisters plumbed into the fuel system. Not the portion feeding gas to the fuel injectors. More to keep the fumes from evaporating into the air from the gas tank. Every now and then the computer shuts the valves closed and allows the purge system to pressurize. If it does not hold pressure then a code is thrown. If the gas cap trick does not work hopefully someone who has fixed the purge valves will chime in.

The O2's are a different story in a sense. This gets into the fuel trims, emissions and such. Might be as simple as new O2 sensors which are likely to be costly. The other problems can be related to running too rich or too lean. Too rich can overheat the catalytic converters and a few other problems. Too lean can damage an engine. What I am leading up to is the question of does the car have an aftermarket tune?

 

[krazer]

Hello; Your car has some purge valves and charcoal cannisters plumbed into the fuel system. Not the portion feeding gas to the fuel injectors. More to keep the fumes from evaporating into the air from the gas tank. Every now and then the computer shuts the valves closed and allows the purge system to pressurize. If it does not hold pressure then a code is thrown. If the gas cap trick does not work hopefully someone who has fixed the purge valves will chime in.

The O2's are a different story in a sense. This gets into the fuel trims, emissions and such. Might be as simple as new O2 sensors which are likely to be costly. The other problems can be related to running too rich or too lean. Too rich can overheat the catalytic converters and a few other problems. Too lean can damage an engine. What I am leading up to is the question of does the car have an aftermarket tune?

Thank you very much for all the information, I’m not sure how I’d know my car is running lean (or not). But I have a scanner that I can see the fuel trims and stuff at the moment of the CEL came on.

that’s correct it has an aftermarket tune, unknown source but no (I know… first mistake) but I got a good deal on this car.

 

[sk47]

it has an aftermarket tune, unknown source but no (I know… first mistake) but I got a good deal on this car.

Hello; Several members have posted threads about serious issues buying cars with an aftermarket tune. Hopefully you got the tuner or at least know what outfit made the tune package.
Well good luck. Hopefully your adventure goes well.

 

[K Myers]

Hello; I get a evap code every couple lf years on my pickup. So far I have "fixed" it by working on the seal of the gas cap. At first I would replace the cap but lately have just replaced to O ring or just cleaned it and slathered on some Vaseline. Have to delete the codes with a scan tool or simply disconnect the negative battery cable for a while.

No clue on the other code. If it is due to O2 sensors they can be a DIY job with the correct tools. I would check the wires and connectors feeding the O2 sensors.
Good

SOUNDS LIKE TO ME THEY RETURNED AS CLOSE TO STOCK AS THEY COULD GET IT, THE PUT THE CATS BACK ON, GO TO THE AUTO PARTS STORE AND HAVE THE RESET IT IF THAT DOESENT HELP IT,YOU MIGHT NEED IT TUNED

 

[krazer]

I'm assuming this bit is your message "SOUNDS LIKE TO ME THEY RETURNED AS CLOSE TO STOCK AS THEY COULD GET IT, THE PUT THE CATS BACK ON, GO TO THE AUTO PARTS STORE AND HAVE THE RESET IT IF THAT DOESENT HELP IT,YOU MIGHT NEED IT TUNED"

Thanks! I'm not sure if I should start there, or replacing the spark plugs.

 

[K Myers]

I'm assuming this bit is your message "SOUNDS LIKE TO ME THEY RETURNED AS CLOSE TO STOCK AS THEY COULD GET IT, THE PUT THE CATS BACK ON, GO TO THE AUTO PARTS STORE AND HAVE THE RESET IT IF THAT DOESENT HELP IT,YOU MIGHT NEED IT TUNED"

Thanks! I'm not sure if I should start there, or replacing the spark plugs.

Not a bad place ro start

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