Check Engine light returns after initial CEL shows misfire

[awai09]

Hi All, just wondering where I should start in the workup of what's actually causing the return CEL of my 2017 DSG GTI with about 38k miles on it. The car is bone stock and has been running well right up until its first CEL last month. A visit to the dealer showed an intermittent missfire (code P0303) just before all spark plugs were changed as part of the 40k service. The code was cleared. The car has driven fine, though the CEL returned (same scenario as first, where it came on shortly after starting the car in my garage and backing out) after a couple hundred miles or so.

I have read on past threads that "bad fuel", plugs, coils, and injectors are the more common causes. My questions have to do with the most efficient (cost and time wise) way to work up the problem and fix it:

1) Would now be a good time to invest in OBDeleven, and assuming yes, can I run it from a Mac laptop?
2) What additive to use - fuel additive (e.g. G001780M3KT) or seafood engine treatment?
3) If coils are the problem - would the S3 coils be more than fine on a stock engine, and would the APR coils add no additional benefit?

Thanks in advance for the replies.

 

[Diggs24]

Shrimp cocktail sauce definitely.

Swap coil 3 to cylinder 2

 

[Diggs24]

If that doesn’t solve it try unhooking the evap line from the pcv. Plug the line with a bolt.

That’s 2 free fixes to try.

 

[jimlloyd40]

Hi All, just wondering where I should start in the workup of what's actually causing the return CEL of my 2017 DSG GTI with about 38k miles on it. The car is bone stock and has been running well right up until its first CEL last month. A visit to the dealer showed an intermittent missfire (code P0303) just before all spark plugs were changed as part of the 40k service. The code was cleared. The car has driven fine, though the CEL returned (same scenario as first, where it came on shortly after starting the car in my garage and backing out) after a couple hundred miles or so.

I have read on past threads that "bad fuel", plugs, coils, and injectors are the more common causes. My questions have to do with the most efficient (cost and time wise) way to work up the problem and fix it:

1) Would now be a good time to invest in OBDeleven, and assuming yes, can I run it from a Mac laptop?
2) What additive to use - fuel additive (e.g. G001780M3KT) or seafood engine treatment?
3) If coils are the problem - would the S3 coils be more than fine on a stock engine, and would the APR coils add no additional benefit?

Thanks in advance for the replies.

You need to get it diagnosed before throwing parts at it.

 

[awai09]

Lol friggin' spellcheck! Good one. "Seafoam" is what I meant.

Swapping coils makes sense to isolate them as a possible cause. This had to be done on my Mk6 years ago to troubleshoot a misfire problem following a stage 1 APR tune.

Sounds like OBDeleven will be a good investment for now and later, especially if the dealer will charge me every time to scan my car.

 

[awai09]

Swap coil 3 to cylinder 2

Just want to say thanks to Diggs24 and jimlloyd40 for motivating me to figure out the problem myself!

I haven't solved the problem yet but I've gotten as far as running a scan with OBDeleven - which showed the same misfire in cylinder 3 - and then swapping coils between cylinder 2 and 3. Next is to drive until the CEL pops up and run another scan.

A couple thoughts:

1) OBDeleven - the OS compatible bluetooth version - is amazingly simple to set up and run. Kudos to OBDeleven. Also, the fact that the dealer charges just over $200 to merely run an engine fault scan is absolute price gouging.

2) YouTube is a great source to learn how to unsnap the coil pack harness without breaking any tabs. Progress!

 

[FooDogg]

Just want to say thanks to Diggs24 and jimlloyd40 for motivating me to figure out the problem myself!

I haven't solved the problem yet but I've gotten as far as running a scan with OBDeleven - which showed the same misfire in cylinder 3 - and then swapping coils between cylinder 2 and 3. Next is to drive until the CEL pops up and run another scan.

A couple thoughts:

1) OBDeleven - the OS compatible bluetooth version - is amazingly simple to set up and run. Kudos to OBDeleven. Also, the fact that the dealer charges just over $200 to merely run an engine fault scan is absolute price gouging.

2) YouTube is a great source to learn how to unsnap the coil pack harness without breaking any tabs. Progress!

Plus 1 on obd2 pro- got mine from Shop DAP with 200 credits, now slowly working my way thru the manual and the obd2 forum...lots to learn.

-skeej

 

[FooDogg]

Hi All, just wondering where I should start in the workup of what's actually causing the return CEL of my 2017 DSG GTI with about 38k miles on it. The car is bone stock and has been running well right up until its first CEL last month. A visit to the dealer showed an intermittent missfire (code P0303) just before all spark plugs were changed as part of the 40k service. The code was cleared. The car has driven fine, though the CEL returned (same scenario as first, where it came on shortly after starting the car in my garage and backing out) after a couple hundred miles or so.

I have read on past threads that "bad fuel", plugs, coils, and injectors are the more common causes. My questions have to do with the most efficient (cost and time wise) way to work up the problem and fix it:

1) Would now be a good time to invest in OBDeleven, and assuming yes, can I run it from a Mac laptop?
2) What additive to use - fuel additive (e.g. G001780M3KT) or seafood engine treatment?
3) If coils are the problem - would the S3 coils be more than fine on a stock engine, and would the APR coils add no additional benefit?

Thanks in advance for the replies.

Bump with advice from another thread on VW tsb on fuel additive: h/t scrllock

https://static.nhtsa.gov/odi/tsbs/2020/MC-10176770-0001.pdf

 

[FooDogg]

RIP, Jim Lloyd.
You will be missed.
We will pay your kindness and patience, forward.

 

[FooDogg]

Hi All, just wondering where I should start in the workup of what's actually causing the return CEL of my 2017 DSG GTI with about 38k miles on it. The car is bone stock and has been running well right up until its first CEL last month. A visit to the dealer showed an intermittent missfire (code P0303) just before all spark plugs were changed as part of the 40k service. The code was cleared. The car has driven fine, though the CEL returned (same scenario as first, where it came on shortly after starting the car in my garage and backing out) after a couple hundred miles or so.

I have read on past threads that "bad fuel", plugs, coils, and injectors are the more common causes. My questions have to do with the most efficient (cost and time wise) way to work up the problem and fix it:

1) Would now be a good time to invest in OBDeleven, and assuming yes, can I run it from a Mac laptop?
2) What additive to use - fuel additive (e.g. G001780M3KT) or seafood engine treatment?
3) If coils are the problem - would the S3 coils be more than fine on a stock engine, and would the APR coils add no additional benefit?

Thanks in advance for the replies.

Another bump with something maybe useful:

https://www.golfmk7.com/forums/inde...-on-ethanol-blends.400683/page-2#post-7824111

 

[FooDogg]

You need to get it diagnosed before throwing parts at it.

Always good advice, by Jim Lloyd, RIP:

here is a useful discussion on diagnosis, and clogged fuel injectors: