CEL cyl 3 misfire P030300

[nestid]

>3 days ago started the car and there was a CEL
> OBDeleven said P030300 cyl 3 misfire
> Replaced the spark plugs and switched around the coil packs
> Cleared the CEL and drove fine for 3 days
> Started the car tonight after driving it most of the day and bam CEL
> Got home, OBDeleven said P030300 cyl 3 misfire once again

This doesn't seem like a coil pack or spark plug issue. Is this the injectors?

Background: 2017 GTI DSG APR Stage I w/ ~44k miles. Car seems to drive fine though

I guess technically I'm still under the 60,000/5 year powertrain warranty (2 months left). But not sure if they'll blame the tune and deny the claim

 

[shovelhd]

How did the cylinder 3 plug look?

I'd eliminate possible grounding issues. Remove the cylinder 3 ground wire from the coil. Use a jumper wire to connect the coil wire to a known good ground point, like the coil next to it or the battery.

 

[nestid]

How did the cylinder 3 plug look?

I'd eliminate possible grounding issues. Remove the cylinder 3 ground wire from the coil. Use a jumper wire to connect the coil wire to a known good ground point, like the coil next to it or the battery.

The plug honestly looked fine. I didn't see anything wrong with it as it looked like the other plugs. I checked grounding using that method and didn't find anything wrong as well :/. I did schedule an appointment at the stealership next Tuesday in the case that I have not figured out the issue

 

[berserker6]

I would do a quick compression test before taking it to the dealership. Inexpensive, quick and informative.

 

[nestid]

I would do a quick compression test before taking it to the dealership. Inexpensive, quick and informative.

I'll run a compression test this weekend. That would determine if it's an injector issue? I've never dealt with these type of issues before so it's new knowledge I'm taking in lol

 

[berserker6]

I'll run a compression test this weekend. That would determine if it's an injector issue? I've never dealt with these type of issues before so it's new knowledge I'm taking in lol

A compression test will tell you if you have a much bigger issue ie: cylinder wall damage, ring issue for example. So ya in a sorta kinda way a good compression result would help point to an injector. What I don't want to see happen is it not being engine issue but the dealership says it is and charges you 10 grand to replace a motor that didn't need replacing. Yeah I guess I have trust issues

 

[JerseyDrew77]

The plug honestly looked fine. I didn't see anything wrong with it as it looked like the other plugs. I checked grounding using that method and didn't find anything wrong as well :/. I did schedule an appointment at the stealership next Tuesday in the case that I have not figured out the issue

Get a borescope and look down in that cylinder to inspect the walls and piston.

 

[nestid]

So update: I don't think it's an injector issue. The car drives perfectly fine with normal MPG, steady RPMs, and no misfires under load. The misfires are intermittent and has only happened the few times at startup. Did some live testing with the OBD connected to try to see if I can log any misfires but weren't able to in the 30 mins of driving with also flooring it. I'm suspecting this is a loose pin in the coil pack harness (the one that connects to the cylinder 3). I tightened the pins in that connection and threw a bit of lithium dielectric grease in it. Hoping this will resolve the issue and I don't have to deal with a $175 diagnostic fee at the stealership if it's not covered under my powertrain warranty.

 

[nestid]

An unfortunate update: CEL came back on tonight at start up after driving around most of the day. Will be taking into dealership tomorrow since I don't have the time to diagnose and fix myself. Hoping that powertrain warranty will cover

 

[YamR1rider]

Keep us posted, hope all works out for you!

 

[nestid]

Tech got back: cylinder walls were fine and no compression/leakage issues. Misfires are sporadic and tech recommends adding a fuel additive and clearing the code. Is that a long term solution? Kind of at a lost for what to do here lol. I'm APR stage 1 high torque 91 octane tune and regularly get 92 octane.

any reccs on additives?

 

[Diggs24]

Fine first course of action. If that doesn't work next would be valve cleaning or injector replacement. As both require removal of intake manifold might as well do both to save on labor costs, unless valves are clearly very clean.

 

[shovelhd]

What Diggs said. For the fuel system cleaner, I always use Chevron Techron.

 

[nestid]

Picked the car back up today. Powertrain warranty covered the $175 diagnostic fee and they added whatever additive in too without me having to pay a dime. Car seems to be driving really well now (not sure if it's placebo or what). No CEL since driving it multiple times today. Fingers crossed. Will update thread if it comes back

 

[nestid]

and we're back with a CEL! it was a good 2 weeks. will scan the code in the morning. actually kind of glad it happened again before january since that's when my powertrain warranty goes away