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It happens right after shutting the car off and then on after a couple of minutes. Goes away if I shut it off and then start again. I have brand new injectors and plugs. Swapped the coils and injectors to see if it followed— it didn’t; still on the same cylinder. Any thoughts? Could it be a faulty lifter?
o2 sensors could cause that as well as they degrade over time. additionally if you're interested in a tune, datalogs would aid in identifying if its in fact an isolated issue.
It happens right after shutting the car off and then on after a couple of minutes. Goes away if I shut it off and then start again. I have brand new injectors and plugs. Swapped the coils and injectors to see if it followed— it didn’t; still on the same cylinder. Any thoughts? Could it be a faulty lifter?
I believe I just suffered this as well last night for the first time.
turned it off, was off for about 45mins then came back and turned it on and it was misfiring like crazy (no check engine light). Turned it off, then
back on like three times and it went away.
this morning I turned it on and as if nothing happened.
In the last 10k miles I have replaced:
-AMG injectors
-New ngk spark plugs per manual
-CCV and intake manifold gasket
-Fuel tank with respective pumps
-All coil packs from AMG
-Intake, exhaust cams and revised SLS lifters.
haven’t had time to check codes to see if something has been stored.
are your o2 sensors new? that can cause misfiring also if they're old. a bad tune can also prematurely kill o2 sensors. with a proper tune they should never go bad.
if you're only seeing misfire on one cylinder though...then it's bad ignition coils or wiring. maybe could be a faulty injector. if you've replaced coils and injectors, there really is no mechanical reason for a single cylinder to misfire. I would then proceed to a compression and leak down. maybe you have a valve stem seal leak.
are your o2 sensors new? that can cause misfiring also if they're old. a bad tune can also prematurely kill o2 sensors. with a proper tune they should never go bad.
if you're only seeing misfire on one cylinder though...then it's bad ignition coils or wiring. maybe could be a faulty injector.
I would have to check what they are reporting via live data. Anyone know what they should be reporting?
yes if you are having multiple misfires o2 sensors could likely be the culprit. they'll only show faulty after the computer runs long enough to lock them out from reporting anything. this can take 5-30 minutes of run time to occur depending on how bad the o2 sensors are. the issue progresses also. it took about 2-3 weeks for me of having to reset the trims before the o2s would be locked out every 30 minutes by the computer. when it locks out, it'll be locked out at a lean or rich position which can cause misfires.
yes if you are having multiple misfires o2 sensors could likely be the culprit. they'll only show faulty after the computer runs long enough to lock them out from reporting anything. this can take 5-30 minutes of run time to occur depending on how bad the o2 sensors are. the issue progresses also. it took about 2-3 weeks for me of having to reset the trims before the o2s would be locked out every 30 minutes by the computer. when it locks out, it'll be locked out at a lean or rich position which can cause misfires.
what values should I be looking for on the o2 sensors to see if they are ok or if they are bad?
gotcha! So off of this Bluetooth obd2 reader I had access to, this is what I have.
seems fine...after driving 30+ minutes they should read the same as shown at idle. also upon acceleration they should be close to each other as far as read out goes. if one is off, it's more than likely the bad one. Equivalence Ratio is your air fuel. Usually lambda but your screenshot is displaying gasoline air fuel which is ok.
seems fine...after driving 30+ minutes they should read the same as shown at idle. also upon acceleration they should be close to each other as far as read out goes. if one is off, it's more than likely the bad one. Equivalence Ratio is your air fuel. Usually lambda but your screenshot is displaying gasoline air fuel which is ok.
Then this is encouraging. Star simply reported “random misfire detected”, never pointed to a cylinder.
My Indy said he reset adaptations since I had swapped coil packs, spark plugs, and injectors to 1. He mentioned could’ve been bad gas.
Since this first happened, it hasn’t happened since and the car is running silky smooth. I guess we’ll see.
Then this is encouraging. Star simply reported “random misfire detected”, never pointed to a cylinder.
My Indy said he reset adaptations since I had swapped coil packs, spark plugs, and injectors to 1. He mentioned could’ve been bad gas.
Since this first happened, it hasn’t happened since and the car is running silky smooth. I guess we’ll see.
Well I’m back to report car experienced the misfires again. This time, check engine light was flashing as they happened and right then and there I turned off the car and scanned with the OBD reader.
when do you see misfires...at idle, acceleration, full throttle, always?
Idle, and during acceleration. I did not attempt full throttle. This is only happening at startup. I have not experienced this while the car is driving normal.
Turn it off and back on a couple of times and it goes away.
idle has been a little bit tough every now and then.
Idle, and during acceleration. I did not attempt full throttle. This is only happening at startup. I have not experienced this while the car is driving normal.
Turn it off and back on a couple of times and it goes away.
idle has been a little bit tough every now and then.
Could the misfire from cylinder 5 have anything to do (or trigger the codes) for cylinder 1 and 2?
if you are certain you are on a factory tune, have new coils, new plugs, new injectors, new cam adjusters, aren't loosing coolant...there isn't anything else that could cause this that wouldn't give you a specific engine code.
if you are certain you are on a factory tune, have new coils, new plugs, new injectors, new cam adjusters, aren't loosing coolant...there isn't anything else that could cause this that wouldn't give you a specific engine code.
Cam adjusters aren’t new. They are still the original ones.
Well yesterday it did the same thing. Went out for a drive got fully warmed up. Turned it off for about 20-30 mins. Turned her back on and she was slightly misfiring. Started driving and it went away. No check engine light.
One observation, as I left the office in the evening I noticed the car is hunting for idle with the AC off.
Could a leak in the intake manifold or hose cause this? Could this be o2 sensors or MAF?
Well yesterday it did the same thing. Went out for a drive got fully warmed up. Turned it off for about 20-30 mins. Turned her back on and she was slightly misfiring. Started driving and it went away. No check engine light.
One observation, as I left the office in the evening I noticed the car is hunting for idle with the AC off.
Could a leak in the intake manifold or hose cause this? Could this be o2 sensors or MAF?
In my case swapping coils didn’t do any good. I replaced them all and the issue is gone. Also, I had to change the spark plugs twice. Apparently had defective one delivered at first. And lastly, if you pull the injector plugs you’ll find oil in there. Spray it off with an electric cleaner or brake cleaner. Sometimes it may cause issues.
Well yesterday it did the same thing. Went out for a drive got fully warmed up. Turned it off for about 20-30 mins. Turned her back on and she was slightly misfiring. Started driving and it went away. No check engine light.
One observation, as I left the office in the evening I noticed the car is hunting for idle with the AC off.
Could a leak in the intake manifold or hose cause this? Could this be o2 sensors or MAF?
bad PCV or deteriorating throttle body plate inside the intake manifold is something else to look for.
so a bad PCV will cause misfires on downshift, and lifting of throttle. it shouldn't cause misfires at idle. over time as it gets worse, you'll start getting lean codes that you would think are the O2 sensors. after replacing the O2 sensors after some time the lean codes will return.
as far as deteriorating throttle body plate, I haven't experienced it myself but I'd assume you would have the same symptoms as above.
I'd imagine if you had both issues they could combine into a random misfire situation.
i would start with replacing your PCV with a lifetime warranty from FCP and pair that with a catch can. those are 2 things highly recommended to do regardless. PCV's last between 50-90k miles before failure.
so a bad PCV will cause misfires on downshift, and lifting of throttle. it shouldn't cause misfires at idle. over time as it gets worse, you'll start getting lean codes that you would think are the O2 sensors. after replacing the O2 sensors after some time the lean codes will return.
as far as deteriorating throttle body plate, I haven't experienced it myself but I'd assume you would have the same symptoms as above.
I'd imagine if you had both issues they could combine into a random misfire situation.
i would start with replacing your PCV with a lifetime warranty from FCP and pair that with a catch can. those are 2 things highly recommended to do regardless. PCV's last between 50-90k miles before failure.
makes sense. PCV was replaced about 7 mths ago though.
So I’ve been doing some data observation. I am seeing my stftb2 move quite a bit from -15%to 10%. Stftb1 is for the most part more stable. Now to the next thing I saw my o2b2 pre cat sensor has a lot more noise than my b1 o2. On idle I can expect a vacuum leak to cause this, but when I held 2k rpms steady for a few mins I see the b2o2 sensor drop while the b1o2 sensor is pretty stable. I am starting to believe my o2 sensor is loosing it and causing the stft to be all over the place.
11-12-2020, 10:27 PM
