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2012 GTI sudden all cylinder misfires?

M

MonLand

New member
Newbie in the GTI world (this is my wife’s car).
She filled up, drive ~20 miles and reported that something did not feel right. That mk6 has ~120K miles and is stock and not driven hard.

today, started the engine and it has a very very rough idle (like “check engine light goes into blinking mode” rough idle). Bumping rpm to 3K is better (but, still feels like it it misfiring). Pushing beyond 4K rpm and engine misses quite a bit (and ends up dying).
check engine light is on and reports misfiring on every/all cylinders literally.
coils were replaced less than 5K miles ago.
since this is sudden and misfiring on all cylinders, I don’t think this is a spark-related issue.
I intend to learn about GTIs and will troubleshoot this myself.
here is what I am thinking:
- vacuum issue
- intake leak

how do I fo about testing those two hypotheses?

Things that I have read that could cause a similar issue:
- timing off (but…. That seems odd with rpm higher masking the issue?)
- pvc valve issue?

codes that seem relevant that lead to my diagnostic eventhough they seem
P0455
Raw code: 0455
ECU: Engine control unit[Archive (inactive)]
Status: Permanent
OBDII: Evaporative emission (EVAP) system - large leak detected
Volkswagen: Evaporative Emission (EVAP) System Leak Detected

============8==============
P0299
Raw code: 0299
ECU: Engine control unit[Archive (inactive)]
Status: Permanent
OBDII: Turbocharger (TC)/supercharger (SC) - low boost
 
Knotical

Knotical

Drag Racing Champion
PCV failures are really common on these cars. Thankfully also fairly cheap and easy to fix. I'd start there
 
M

MonLand

New member
Knotical said:
PCV failures are really common on these cars. Thankfully also fairly cheap and easy to fix. I'd start there
Click to expand...
That’s what I read. Though, when I pulled the oil cap yesterday, there was pretty good suction on it which seems to indicate the PCV system is mostly ok? Or this is not enough to rule that part out?

also, since it’s due, I’ll also replace the fuel filter. But I don’t think that would cause misfires? (Well…. I guess I’m not sure if a fueling issue would cause misfires; bad gas is possible, but I’m not sure my wife would be that unlucky on an Exxon station)
 
M

MonLand

New member
a few details that might or not matter:
- water pump was replaced ~3 weeks ago
- at the same time SAI was looked at, air pump verified to work, SAI combi (kombi?) valve cleaned up but not checked to actuate and is now suspected to be the SAI engine code source.
 
M

MonLand

New member
So….. looking at the combi valve area, I noticed that I might have forgotten to install (or tighten?) the top bolt. It appears that there is a bolt missing on there. Could that be the cause for the behavior I’m seeing?

not quite sure what the impact is. That might be equivalent to a small exhaust leak?
 
king1138

king1138

Go Kart Champion
I know it's a silly thing to check, but an EVAP leak code and rough running right after a fuel up could mean the gas cap is not installed or not tight. I'd start there. You may also want to call the gas station to ask if they've had any reports of bad fuel problems. Every now and then a gas station will get bad fuel (or the wrong fuel, like diesel) delivered or put in the wrong tank. This will cause all manner of issues. Often times the gas station will pay for repairs if that's the case.
 
B

BudgetPhoenix

Autocross Champion
On the right side of the circular pcv cap there is a small pinhole. Feel if it is sucking air with the engine running. If so the diaphragm inside is blown and causing a vac leak. Probably most common vac leak. The pcv can go bad in other ways too internally so not always the sure way to tell but it's a good start.
 
M

MonLand

New member
Ok. So today I went back to basics:
- new plugs (old one had a significant layer of carbon/soot on them; thought they had been replaced ~6-9 months ago with the coil pack…. Maybe not? Maybe due to misfire?)
- emptied gas tank and refilled with new gas (could not get a hold of the gas station guys… :/ now I would know how to replace the fuel pump! ;) )
- put the missing bolt on combi valve
- replaced air filter
I did also replace the head cam position sensor (oil was seeping, and apparently you can’t just buy the O ring).

unfortunately, none of those steps helped.

In my part stash now I have and I’ll install if it makes sense/based on next steps.
- crank shaft sensor
- PCV assembly
- fuel filter (not the issue, maintenance item. Just due)
- coil packs (they were replaced 6-9 months ago, so I don’t think those are a problem)
 
M

MonLand

New member
BudgetPhoenix said:
On the right side of the circular pcv cap there is a small pinhole. Feel if it is sucking air with the engine running. If so the diaphragm inside is blown and causing a vac leak. Probably most common vac leak. The pcv can go bad in other ways too internally so not always the sure way to tell but it's a good start.
Click to expand...
And this can lead to misfires, right?
 
M

MonLand

New member
king1138 said:
I know it's a silly thing to check, but an EVAP leak code and rough running right after a fuel up could mean the gas cap is not installed or not tight. I'd start there. You may also want to call the gas station to ask if they've had any reports of bad fuel problems. Every now and then a gas station will get bad fuel (or the wrong fuel, like diesel) delivered or put in the wrong tank. This will cause all manner of issues. Often times the gas station will pay for repairs if that's the case.
Click to expand...
Nothing is silly! Today I removed and rejnstalled the gas cap. Seal looked fine. Let’s see if the evap code goes away.
Emptied tank, put new/different gas in it and issue did not go away after running the engine for ~1-2 mins. So I’ll rule out the fuel issue for now.
 
M

MonLand

New member
Today I discovered that I had not locked the bottom of the air intake so it opened up and must have caused issues since this means that the air intake being measured was incorrect….
i was hopeful and put everything back together.
but, while this helped, this dis not fix the issue.

i can’t figure out how to check the timing in case the chain jumped one tooth.


============1==============
P0300
Raw code: 0300
ECU: Engine control unit
Status: Confirmed
OBDII: Random/multiple cylinder(s) - misfire detected
Volkswagen: Engine Misfire Detected

============2==============
P0301
Raw code: 0301
ECU: Engine control unit
Status: Confirmed
OBDII: Cylinder 1 - misfire detected
Volkswagen: Cylinder 1 Misfire Detected

============3==============
P0303
Raw code: 0303
ECU: Engine control unit
Status: Confirmed
OBDII: Cylinder 3 - misfire detected
Volkswagen: Cylinder 3 Misfire Detected

============4==============
P0304
Raw code: 0304
ECU: Engine control unit
Status: Confirmed
OBDII: Cylinder 4 - misfire detected
Volkswagen: Cylinder 4 Misfire Detected

============5==============
P0302
Raw code: 0302
ECU: Engine control unit
Status: Confirmed
OBDII: Cylinder 2 - misfire detected
Volkswagen: Cylinder 2 Misfire Detected

============6==============
P0491
Raw code: 0491
ECU: Engine control unit
Status: Confirmed
OBDII: Secondary air injection (AIR) system, bank 1 - malfunction

============7==============
P0016
Raw code: 0016
ECU: Engine control unit
Status: Confirmed
OBDII: Crankshaft position/camshaft position, bank 1 sensor A - correlation
 
M

MonLand

New member
In term of symptom, beside the codes:
- idle is not the best and jump quite a bit. Check engine light will light up and blink at idle (and disappear if you accelerate).
- if you bring up rpm to 1500+ rpm, you can feel/hear some misfiring, but it’s not that obvious anymore.
 
M

MonLand

New member
BudgetPhoenix said:
Check the EVAP purge valve on the front side of the intake manifold. Loose hose connection and occasionally they fail
Click to expand...
So…. I verified that, engine stopped, I have very good vacuum holding on the evap valve.
however, I can blow into the gas tank without any issue. I thought the gas tank system would be pressurized? Is that because I can’t blow into it (with my lungs) enough to pressurize it?
 
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