Help! Misfire and Very Rough Idle

[Grey15boost]

Current problem with car: rough idle all the time whether cold start or hot. After a minute of idling the car will get very choppy and a/f will drop too 16-18, and lean out. Upon acceleration blinking check engine light goes on and does not level its self back out. I then turn off the car and take off again and all though it's still a little choppy, a/f will hangout at 14.5 on the highway and drive smooth. Very confused with what is going on. Throwing codes after all of this:

P0302: Excess emissions level of misfire detected in cylinder no. 2

P0300: Random Misfire Detected

P0301: Misfire- Cylinder 1

P04DB: Crankcase Ventilation System Disconnected

P051D: Crankcase Pressure Sensor Circuit High

P0137: 02Circuit Low Voltage (Bank 1, Sensor 2)

P0141: HO2S-12 (Bank 1, Sensor 2) Heater Circuit Malfunction

Modifications: Stainless works Catless Downpipe and Exhaust, on 3 Performance Intercooler, hard pipe and Blowoff valve, Cobb 93 Tune.

If anyone has any idea or similar problems, I would appreciate the information! Thanks

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[Ecoboosted15]

Might need to return the car's programming to stock and take to dealer. May have some issues that need to be addressed. Make sure you haven't unplugged any sensors or connectors to the coils and pcv ventilation tubes/sensor as well.

 

[PRG3k]

Very simple but have you checked your plugs? Rough idle and misfires can be signs of fouled plugs. Also surprised you have all those mods with no catch can.

 

[BrewCityBOOST]

plugs and/or gap likely need to be changed to resolve the missfires. gap to .030", i recommend NGK 6510 plugs.

the o2 sensor stuff obviously from your catless downpipe. hit me up if you want a tune to turn that off. we have SCT X4 and custom tune for $399.

have you touched, or done anything to your pcv system? some of those codes have popped up for people who have.

good luck!

 

[Edkiefer]

I agree with all the above posters, plugs would be first check.

One thing though, on "P0141: HO2S-12 (Bank 1, Sensor 2) Heater Circuit Malfunction"
That is the heater part of O2 sensor and should be getting 12v no matter the exhaust quality so I would check tightness of O2 sensors and the O2 plug connection (I don't know which O2 sensor that is, others for sure would know).

 

[Damndave]

plugs and/or gap likely need to be changed to resolve the missfires. gap to .030", i recommend NGK 6510 plugs.

the o2 sensor stuff obviously from your catless downpipe. hit me up if you want a tune to turn that off. we have SCT X4 and custom tune for $399.

have you touched, or done anything to your pcv system? some of those codes have popped up for people who have.

good luck!

The guy is running a Cobb Accessport, I highly doubt buying an sct tuner and tune at this point is what he's looking to do, let him contact Cobb first and see what the issue is rather than you selling hi a product. I get your trying to make money, but it would be nice to see if the guy can fix the issue at hand. Plus if he's already got a Cobb, he should talk to Adam and see what can be done after Cobbs help. Sometimes it's what's best for the customer, vendors.

 

[chadhtx40]

BrewCityBoost probably just simply missed the Cobb93 tune comment. I agree with the statements check the plugs, make sure the ceramic tips didn't go to hell on you. NGK and Denso seem to be the popular choice. Denso's however have worked better for my MT PP than NGKs.

 

[Damndave]

BrewCityBoost probably just simply missed the Cobb93 tune comment. I agree with the statements check the plugs, make sure the ceramic tips didn't go to hell on you. NGK and Denso seem to be the popular choice. Denso's however have worked better for my MT PP than NGKs.

It's not just them and I'm not singling them out, I notice a lot of vendors try and sell and push there products on pages where people are asking for help. It would be nice to see some non biased answeres every once in a while from these guys, because they have a lot of knowledge and can help if it wasn't all about an add to buy this buy that. Adam is prob one of the few who never does that kind of shit. I know there's others, just sayin. I promise they didn't miss the fact the guy has a Cobb, second it doesn't fix the problem, and third when they say try checking your plugs, and oh by the way we sell them over here, that's what I'm talking about.

 

[Grey15boost]

Thank you all! Plugs were definitely the issue. Ceramic tips did go to hell on cylinder 2 lol. I bought this car with all the mods done, obviously the previous owner didn't take the safety measures as far as oil catch can and better plugs. Lesson learned, car is now running great again. Thank you for all the replies, I am a little new to this and didn't even think about checking the plugs.

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