Misfires, no codes

[foxbyt3]

Hey all! A few weeks ago my 2012 GTI started misfiring. The misfires happen at full throttle. When they do happen if I release the throttle to around 90% the misfires stop and the car continues to accelerate normally.

I ordered up new coils and plugs but the issue persisted. Next I took her to my local shop for a closer look and they found carbon buildup which they then cleaned out. While doing that they also replaced the fuel injectors for good measure. I found some buildup in the air intake were the crank case hose connects and cleaned that out.

Unfortunately the misfiring is still happening. I've ran her hard a few times and doing an "Italian tuneup" but the issue continues.

I'm thinking of replacing the PCV and/or Crankshaft Position Sensor next.

Wondering if anyone has recommendations for further troubleshooting steps?

 

[DASVDUB]

Sounds like a possible boost leak?


Sent from my iPhone using Tapatalk

 

[foxbyt3]

Sounds like a possible boost leak?

Thanks! Didn't consider a boost leak could cause this. Good excuse to pick up a boost gauge

 

[BudgetPhoenix]

How do you know they are misfires?

 

[foxbyt3]

How do you know they are misfires?

The shop who cleaned the carbon buildup hooked it up to a computer and drove it around and they were able to see a misfire occur in cylinder 1.

I have an OBDeleven reader I haven't connected up during driving yet. I trust the mechanics at the shop, ive been taking my car there for years now, but I guess I should confirm their findings myself.

My butt sensor tells me its very brief loss of power, so I assumed misfires.

 

[BudgetPhoenix]

Ah okay. If you have OBD eleven you should be able to monitor the live measuring blocks as well for misfires yourself. In the engine module go to block 14 it shows total misfire count and and if I recall block 15 shows cyl 1-3 individual misfire count and 16 shows cyl 4

 

[foxbyt3]

Ah okay. If you have OBD eleven you should be able to monitor the live measuring blocks as well for misfires yourself. In the engine module go to block 14 it shows total misfire count and and if I recall block 15 shows cyl 1-3 individual misfire count and 16 shows cyl 4

I appreciate the info! I'm still learning to use the OBDeleven. I should be able to get it hooked up this weekend and tested. Ill report back my findings.

 

[foxbyt3]

Some new info; car just started making a rattle sound yesterday. Sounds just like the timing chain rattle, and the sound is coming from that area... Unsure if these issues are related, but either way i'll be getting the car into the shop ASAP. Might have them check boost while they're at it.

 

[Timer]

I have the same issues with carbon build up, misfires etc. Have had a lot of work done to the car lots of new bits but it’s still running rich and misfiring, I’m getting a code P0172, have you any info on any codes you got from this?

 

[foxbyt3]

I have the same issues with carbon build up, misfires etc. Have had a lot of work done to the car lots of new bits but it’s still running rich and misfiring, I’m getting a code P0172, have you any info on any codes you got from this?

For code P0172 have you checked the recommendations here - https://www.obd-codes.com/p0172

If you have a VCDS or OBDelleven id recommend running some diagnostic logging. I ran APRs recommendation - https://www.goapr.com/support/datalogging.php I ran this to try and identify boost leaks but only found misfires. Heres a good video on using the OBDeleven -

I didn't get any codes in my troubleshooting, wish I did. After all the troubleshooting I did it ended up the cheapo coil packs from Amazon I initially purchased to fix the misfiring issue continued to cause the issue.

 

[Mk6 Steve]

$100 PayPaled to anyone that can figure this out, intermittent misfires under wot after ~30 minutes of driving or 4-5 consecutive wot pulls, whichever comes first. I get misfires under wot only with no codes. Parts thrown at it....lpfp, hpfp, fuel pump control module, fuel filter, injectors, R8 coils, plugs, diverter valve, cam and crank sensor, maf, map sensor, boost leak tested (I reach peak boost)....I’m starting to lean towards timing chain stretch. Car drives great with the exception of most wot pulls, occasionally no misfires???? Wtf! The only thing I haven’t changed in the fuel system is the high pressure fuel sensor....anyone want to take a stab at this?

 

[svickstc]

Check your block 093 under engine control module for the reading this has been shown to indicate timing chain stretch.

After all that work you threw at the car and still have misfires have you had carbon cleaning ever?or buy a cheap cam scope and check out the valves?

Maybe a catch can might help at this point in the game

 

[Mk6 Steve]

Carbon cleaning and new intake manifold installed about 25k, another carbon cleaning roughly 10k miles ago

 

[Mk6 Steve]

I have an 034 catch can and Africa plate

 

[svickstc]

What tune are you running assuming those mods you’re staged at this point. Do some VCDS logs