30,000 miles and throwing an occasional cylinder 6 misfire

[treejs4]

A little back story, I have a 2014 with a unitronic stage 2 tune for the past 20,000 miles (no issues ever) and I just recently installed awe non-res downpipes and track exhaust. When I installed the exhaust components, about a week later I threw a cel which I diagnosed as a cylinder 6 misfire which happened 37 seconds after start-up. Went a few weeks, not driven much, and again threw the same code. I cleared it again and it has not popped up but Could this be related to the exhaust install? Or could it be that I need the updated tune, stage 2+ from unitronic now that I have the downpipes installed. Could my plugs need to be changed early since it is tuned?

Just looking for some help and ideas. I don't believe it is bad gas since the misfire was in the same cylinder both times.

[shoe3k]

Sounds like plugs to me. The downpipes wouldn't require any additional tuning.

[schirm]

When I had cyl 6 misfire I had a clogged catalytic converter. But check the cheaper options first.

[treejs4]

So I am still having this intermittent issue.

I swapped the coil packs with cylinder 5 first and still had a misfire in 6. Then I swapped the plugs and same thing.

The CEL recently came on this weekend and I left it on for the weekend and when I went to take the car to my friends house to VAG-COM it last night, the light went off. When we hooked it up to the VCDS, it was showing a really intermittent misfire. For example, we sat in the car for 10 minutes and cylinder 6 had only 7 misfires.

Not sure what I should check next :-/

On a side note, this only started happening after I installed my AWE non-resonated donwpipes and track exhaust. Could it be something related to that? I have been tuned for over a year and half too.

[Sceanzo]

Intercooler has hole in it. Dumping coolant into cylinder 6

[treejs4]

Intercooler has hole in it. Dumping coolant into cylinder 6

How could I confirm this?

[Sceanzo]

Spark plug could have white crusty residue. A pressure test of the coolant system would be the best way.

[treejs4]

Spark plug could have white crusty residue. A pressure test of the coolant system would be the best way.

When I swapped my cylinder 6 plug with cylinder 5 they both had a little bit of frost on them.

[BoostEasy]

What did the plugs look like?

Are the downpipes catless or high-flow cats?

DI engines are very fussy about fuel air ratio and injection event timing which if either is off will causes misfires.

Under what load/RPM are the misfires occurring?

[treejs4]

What did the plugs look like?

Are the downpipes catless or high-flow cats?

DI engines are very fussy about fuel air ratio and injection event timing which if either is off will causes misfires.

Under what load/RPM are the misfires occurring?

The plugs didn't seem too bad (i.e a little black around the rim and a very little white frost on the end).

The downpipes are AWE non-resonated so I still have the stock cats in.

I don't know off the top of my head what rpm it was at, but I know it typically occurs during idle. The first time it happend was 37 seconds after start up but the car was already warm from running 20 minutes prior.

[bhvrdr]

I would agree that it is worthwhile to pull the supercharger and check for any leaks. When there have been failed intercoolers it has always been around cyl 6.

Mike

[treejs4]

Does anyone else find it odd that this just started happening after I installed the downpipes and exhaust though?

[BoostEasy]

The plugs didn't seem too bad (i.e a little black around the rim and a very little white frost on the end).

The downpipes are AWE non-resonated so I still have the stock cats in.

I don't know off the top of my head what rpm it was at, but I know it typically occurs during idle. The first time it happend was 37 seconds after start up but the car was already warm from running 20 minutes prior.

Nothing easy to check for other than maybe pulling the SC and checking for a leak as Mike and others already suggested.

I wouldn't be surprised if it was the fuel injector but changing those is almost certainly a dealer visit.

It's hard to say how the exhaust would have impacted things but possibly if an O2 sensor/wire was damaged somehow but that should ideally throw an O2-specific code I would think.

[treejs4]

Nothing easy to check for other than maybe pulling the SC and checking for a leak as Mike and others already suggested.

I wouldn't be surprised if it was the fuel injector but changing those is almost certainly a dealer visit.

It's hard to say how the exhaust would have impacted things but possibly if an O2 sensor/wire was damaged somehow but that should ideally throw an O2-specific code I would think.

If it is an injector, do you guys think it would be worth while throwing some fuel additive injector cleaner in like Startron ?

[BoostEasy]

If it is an injector, do you guys think it would be worth while throwing some fuel additive injector cleaner in like Startron ?

I have my doubts it would do anything as gasoline by itself is a pretty strong solvent but opinions vary.

Some small silver lining may be that in order to replace the injector you'll have to pull the SC (or at least lift it). So at that time perhaps it will be noticeable if there was a small IC leak inside the SC case over cyl #6.

Have you tried flashing it back to stock to see if it is tune related? That would be worth trying before bringing it in to the dealership which you'd have to remove the flash anyways.

[treejs4]

I have my doubts it would do anything as gasoline by itself is a pretty strong solvent but opinions vary.

Some small silver lining may be that in order to replace the injector you'll have to pull the SC (or at least lift it). So at that time perhaps it will be noticeable if there was a small IC leak inside the SC case over cyl #6.

Have you tried flashing it back to stock to see if it is tune related? That would be worth trying before bringing it in to the dealership which you'd have to remove the flash anyways.

I most likely am leaving the dealership for a last chance thing. As I said, it is a very minimal misfire that more than anything just annoys me.

If I pulled the supercharger, what exactly would a leak look like as I thought coolant flowed through it anyways?

And I haven't flashed back to stock because the tune has been fine for over 1.5 years so I highly doubt it is that.

[BoostEasy]

I most likely am leaving the dealership for a last chance thing. As I said, it is a very minimal misfire that more than anything just annoys me.

If I pulled the supercharger, what exactly would a leak look like as I thought coolant flowed through it anyways?

And I haven't flashed back to stock because the tune has been fine for over 1.5 years so I highly doubt it is that.

How long does it take to flash/reflash unitronic? I guess it never sounds difficult when you're making someone else do the work...

If you pull the SC there should be some sort of pink or white residue going down into the #6 intake port into the head if it's leaking enough to bother it. Idle will have the most vacuum so the leak should be most prevalent during idle and off-throttle.

I've never tried it, but it may also be possible to pressurize the SC cooling loop somewhere like the bleed screw on the intercoolers on the back of the SC. You'd need a mityvac/vacuum pump and a fitting that would screw into the bleed screw threads with a host barb on top for the pressure pump. Then pump it up a little bit and see if the pressure drops and at what rate. The trouble is it might leak pressure a little bit stock so it'd be hard to tell unless you compared it to a stock car known not to leak.

[Sceanzo]

Coolant flows through the intercoolers not out of it. If you pull the coolers and find pink crusty residue on the fins by cylinder 6 port, it's leaking. Pulling the charger is fairly simple.

[bhvrdr]

Coolant flows through the intercoolers not out of it. If you pull the coolers and find pink crusty residue on the fins by cylinder 6 port, it's leaking. Pulling the charger is fairly simple.

This is a good point. Its relatively easy and if there is a leak, finding it early is quite a payoff. In other words, it could be worth it not to ignore.


Mike

[treejs4]

This is a good point. Its relatively easy and if there is a leak, finding it early is quite a payoff. In other words, it could be worth it not to ignore.


Mike

So if I pulled the SC and did find a leak, what am I looking to replace from the intercooler?