RyanC93

Hi everyone. I’ve owned my 2012 c63 for 3 months now and have aftermarket air filters. Decat the primary and secondary cats and had a stage 2 remap. The car only made 500 bhp on the dyno and afterwards we found that the car has misfires on all cylinders. We reverted the map back to standard and the problem is exactly the same . Has any one came across this before ?

Thanks in advance Ryan

BLKROKT

Run the codes

RyanC93

Code #1

Code #2

Code #3

RyanC93

Sorry i forgot to say the car doesn’t misfire for first 10 minutes then starts to do it once it’s hot

PeterA90

How many miles on your car?

if you’ve tuned the car back to stock. Changed all
o2’s plugs and coils. The only thing it can be is a sensor Ie: map, cam sensor, MAF, etc. or worst case cam adjusters

RyanC93

Thanks for your reply. The car has just hit 54,000 miles . I returned the car to stock to see if it was misfiring and when it was we loaded the map back onto it.

I’ve just bought the spark plugs to fit and if it was a bad coil what could be the chance that all 8 would develop a misfire ?

would there be anyway to check the sensors before spending loads of money, I’ve read the 02 sensors can go back but they’ve been mapped out because of the decats I think?

thanks

AMGonFire

Get new primary o2s. There are a total of 4 the rear 2 get mapped out so as not to set check engine light when your catless. They only function as telling the ecu the cats are working or not. The primary o2 do all the work of a/f ect and will cause random multiple misfires when they are bad.

hachiroku

^ i concur. faulty primary oxygen sensors will cause misfires. i also did have 1 sensor that was on its way out that would cause fuel trims to go all out of whack randomly. when it would go too far one way engine would start missing. enough of this and you'll eventually get a check engine. drove around for 2-3 months until it went kapoot and would peg rich or lean after 20 minutes or more of driving.

roadtalontsi

intake or intake gasket leaks. then replace oxygen sensors. mixture adaptation tells it all if thats with the stock tune.
500bhp isn't "bad" dont be fooled by the 500whp header tune posts. Ask them what their ET is lol. Also not all tunes and tuners are created equal just like dynos.

hachiroku

be careful with your comments. a xxxxx had the admins threaten to ban me. also all my posts are gone.

RyanC93

Thanks again guys. My mapper told me that the 02 sensors have been mapped out so they do not cause a engine check light as I’m completely catless. But I am assuming that they have a function like yous say to send the correct information back to the ecu?

does it sounds like mine are going bad, as they are fine for first 10/15 mins? And would they check up any codes or just the misfire counter like the photo I posted

BLKROKT

All your tuning posts? Please explain.

Jasonoff

Isn't it obvious? You have to be a sponsor to innovate up in this joint...

BUT, if you're a sponsor you can sell absolute junk no probs!

Solo wing

During a cold-start the engine runs in open-loop (no feedback from O2 sensors) until it reaches optimal temperature. After that it switches to closed-loop and takes input from the O2 sensors.
This might be the reason it runs fine at first.

hachiroku

also the factory computer has diagnostic functions that test the sensor by altering trims. the further off the resulting readings are the further the ECU swings trims. it does this to determine health of the sensor. at some point the trims will be so far off misfiring will begin occuring. additionally once the computer determines the sensor is faulty. it will lock the long term trims to the last value presented prior to check engine light. what that means is you can be locked super rich or super lean which can cause misfire or engine damage long term. the diagnostic function in my eyes should determine final lock between this value or with factory defined mappings based off other sensors and run values but it does not.

RyanC93

Thanks again for the replies.

i changed all the spark plugs today (which was much easier then I thought but I don’t think it has cleared the problem , tomorrow I’m going to change oil to 5w40 as it’s 5w30 for some reason at the minute as the merc dealer said it should be 5w40)

do you guys know if it’s just the primary sensors I could be looking at or do the secondary’s also send information back to the ECU?

and is there any way to test the sensors are ok without just buying new ones? sorry for All the questions .. only had the car a few month!

hachiroku

secondarys are only for monitoring status of catalytic converters

BLKROKT

2 days in a row people have had a 30w in their engine? What’s going on, don’t people read the owners manual anymore?
How long has that been in your engine?

RyanC93

So the primary’s don’t monitor the cats at all? And the secondaries can’t cause the engine to misfire ?

and I think for since the last service what unfortunately was 6k ago . I questioned the garage I bought it from and he said it was Right and was 5w30.ive for 5w40 millers nanodrive going in . The car literally warms up in a minute ..

BalanBro

Correct. Primaries measure AFR before the converters to adjust fueling fuel trims. These could cause misfires if they are bad. The downstream O2 sensors are only there to make sure your converters are actually working. They are not used for fueling at all.

BLKROKT

Just for reference here are the Mercedes approved oils for the C63. Do yourself a favor and choose something from the list and save yourself more headache.

https://bevo.mercedes-benz.com/bevol..._en.html#close

RyanC93

Thankfully the sensors don’t look to expensive.. is the only way to tell if there bad is the codes? All it has is random misfires on all cylinders and no codes.. don’t know what else it could be

and what head aches Are you talking about 😟? I’ve already bought the oil now Lol.. ran it in my big turbo cupra for years with out any problems

BLKROKT

Suit yourself. Is your oil on the list? No. For the record, whatever you ran in your Supra has exactly zero relevance as to what’s best for the M156.

hachiroku

Seat/Leon Cupra is a Spanish version of the VW Golf GTI 1.8t from what I recall.

Jasonoff

I believe they do contribute to LTFT, although very minor.

There was a detailed thread about it a while back. Maybe by @Vladds ?