[Agentphish]

Hey everyone...

I just had my valve cover (not gasket) officially known as the cylinder head cover, part # 11127552281 as listed on RealOEM replaced due to continued slight leaking after the valve cover gasket was replaced several months ago. (dealer found a hairline crack in the cover itself) I've noticed since this was replaced that on warm starts the car seems to be rough/struggling/hesitation at start. There's a noticeable shake to the car when I'm sitting in it that wasn't there before.

Seems to smooth out and run fine after 15-20 seconds of running at idle and driving around town and on the highway has no sign of issue. Just looking thoughts on why this might be happening.

I tried to shoot some video from inside and outside of the car but nothing is really picking up the rough/struggling/hesitation at start.

[Agentphish]

Turned out to be coils 4 & 6 firing but at lower output than the rest of the coils. Not causing a code, but causing intermittent misfire and knock and rough idle.

All coils are getting replaced.

[GoRomeo]

Originally Posted by Agentphish

Turned out to be coils 4 & 6 firing but at lower output than the rest of the coils. Not causing a code, but causing intermittent misfire and knock and rough idle.

All coils are getting replaced.

Thanks for sharing. Keep us posted.

[e92_enthusiast_1]

That's interesting. How would one diagnose a coil like that? Genuinely curious. Is there a tool one could use or does the cars DME save this info and you can pull it through dis/inpa?

Originally Posted by Agentphish

Turned out to be coils 4 & 6 firing but at lower output than the rest of the coils. Not causing a code, but causing intermittent misfire and knock and rough idle.

All coils are getting replaced.

[Agentphish]

Originally Posted by e92_enthusiast_1

That's interesting. How would one diagnose a coil like that? Genuinely curious. Is there a tool one could use or does the cars DME save this info and you can pull it through dis/inpa?

When I dropped it off, he told me he "since it's possible the DME wasn't showing any codes and may not be able to detect a fault I'm going to hook it up to my diagnostic equipment and be looking at the raw data."

He then told me this morning that coils 4 & 6 were firing weaker than the rest and he's replacing all of them to prevent any need for a repeat visit (My CPO is up in 2-3 days anyway) and because I've talked about this issue with him several times in the past and he was unable to find anything stored in the DME.

Im just thankful he's awesome and got to the bottom of it. It's my impression this took him a good amount of time.

[Agentphish]

Originally Posted by GoRomeo

Thanks for sharing. Keep us posted.

You are very welcome. Anything that helps the community.

[e92_enthusiast_1]

Excellent, thanks for the follow up.

Originally Posted by Agentphish

When I dropped it off, he told me he "since it's possible the DME wasn't showing any codes and may not be able to detect a fault I'm going to hook it up to my diagnostic equipment and be looking at the raw data."

He then told me this morning that coils 4 & 6 were firing weaker than the rest and he's replacing all of them to prevent any need for a repeat visit (My CPO is up in 2-3 days anyway) and because I've talked about this issue with him several times in the past and he was unable to find anything stored in the DME.

Im just thankful he's awesome and got to the bottom of it. It's my impression this took him a good amount of time.

[Sandman614]

Any idea of what said diagnostic equipment/raw data is?

I remember seeing a while back some one testing their coils with a voltmeter but then some one else said that wasn't completely accurate...

[Agentphish]

Originally Posted by Sandman614

Any idea of what said diagnostic equipment/raw data is?

I remember seeing a while back some one testing their coils with a voltmeter but then some one else said that wasn't completely accurate...

Nope.

[GoRomeo]

I would like to test mine too. I am still running on originals so they are about 9 yrs old. I changed the spark plugs myself last year but not the coils as they looked goods still.

I will look online but if somebody has a procedure how to test these let me know...

[Agentphish]

Originally Posted by GoRomeo

I would like to test mine too. I am still running on originals so they are about 9 yrs old. I changed the spark plugs myself last year but not the coils as they looked goods still.

I will look online but if somebody has a procedure how to test these let me know...

If he'll explain in more detail I'll let you guys know.

[Agentphish]

Originally Posted by e92_enthusiast_1

Excellent, thanks for the follow up.

Originally Posted by Sandman614

Any idea of what said diagnostic equipment/raw data is?

I remember seeing a while back some one testing their coils with a voltmeter but then some one else said that wasn't completely accurate...

Originally Posted by GoRomeo

I would like to test mine too. I am still running on originals so they are about 9 yrs old. I changed the spark plugs myself last year but not the coils as they looked goods still.

I will look online but if somebody has a procedure how to test these let me know...

He said he went back to the basics. Stuff a lot of newer technicians and DIYers don't necessarily understand that well or in some cases at all. People become to reliant on computer diagnostics to tell them whats wrong instead of learning specifics and manual triage.

Coming from a computer service background in my teens/twenties, I agree with him. I knew a lot of the older hands on troubleshooting techniques. A lot of my younger employees only understood how to run a diagnostic and read the results. Glad not to be in that industry any longer.

Anyhow, he said he used a kV Adapter between the coil and the plug, Oscilloscope and his eyes. Aparently a lot can be learned by looking at primary and secondary spark firing lines, comparing them to the data gleaned from the kV Adapter and Oscilloscope. You just really have to know what you're doing. In my case, it became clear to him that these two coils were not providing the necessary kick.

I guess this kind of thing is why he's a BMW Senior Master Technician. I'm just glad to know him.