Rough idle, random cylinder misfires - do I have it right?

[trandg]

I have a 2007 GTI Stage 1 at approx 115,000 kms.

Lately, it's been acting a little funny:
-it has a rough idle, where the revs surge double the normal levels (starts at 800rpm and then surgest to 1600 or so off and on)

-the heads up display is showing me worsening fuel mileage than it used to: would often say I have 500km on a tank at full, now will say 400-450km

-when the air conditioning is on, there is a very loud fan sound that turns on. When I turn off the car, the fan winds down but is still fairly loud. My mechanic said it wasn't an issue but wondering if others have seen this.

Videos:
Fan sound while engine and A/C is on
Fan sound when engine and A/C just turned off
Engine only

The check engine light is on and this was the readout:

Current Fault Log
------------------
P0300: Random/Multiple Cylinder Misfire Detected
P0302: Cylinder 2 Misfire Detected
P0304: Cylinder 4 Misfire Detected

Pending Fault Log
------------------
P0171: System too Lean (Bank 1)
P0301: Cylinder 1 Misfire Detected
P0303: Cylinder 3 Misfire Detected
P0507: Idle Control System RPM Higher Than Expected

From what I've read on the forum it seems as coils/plugs are a possible fix, as would a PCV fix.

Any suggestions on how to approach this? Should I just replace the plugs and coils or should I be testing a few things first before I do it? Same thing with the PCV...

Thanks for your help!

 

[ROH ECHT]

Can you post the date and time relating to each code...usually the first code that appeared is responsible for the latter. Otherwise you could be sent down a road to correct things that may not need to be addressed :thumbsup:

 

[Das Gespenst]

Only 3 things come to mind. Intake runner flap motor failure, would cause your idle issue, bad coils and or plugs, would cause the miss fire issue, or carbon build up on valves, would lead to both issues. Something to start with at least.

As Roh stated, relevant time to codes would help narrow it down.

 

[trandg]

Hi guys,

thanks for the quick responses. I don't have timing on the codes - it was all done today on one single test around 5pm. I can download a different app and see if I can get the readout with time stamping. Will check it out tomorrow and post what I find.

 

[trandg]

Any suggestions on what apps could get time codes? I downloaded the top ten apps on Android for odb2 and none gave times associated with codes. Or is there another way to check for times with the codes?

I did another check with the Torque app and it gave back this:

Current Fault Log
------------------
P0300: Random/Multiple Cylinder Misfire Detected
P0301: Cylinder 1 Misfire Detected
P0302: Cylinder 2 Misfire Detected
P0303: Cylinder 3 Misfire Detected
P0304: Cylinder 4 Misfire Detected
P0507: Idle Control System RPM Higher Than Expected

Pending Fault Log
------------------
P0171: System too Lean (Bank 1)

Historic Fault Log
------------------
ECU reports no historic faults
Other discovered fault codes
(possibly pending, current or manufacturer specific)
----------------------------------------------------
ECU reports no other fault codes logged


Thanks!

 

[donjuan1jr]

Change your pcv.

 

[clockwise33]

Any suggestions on what apps could get time codes? I downloaded the top ten apps on Android for odb2 and none gave times associated with codes. Or is there another way to check for times with the codes?

I did another check with the Torque app and it gave back this:

Current Fault Log
------------------
P0300: Random/Multiple Cylinder Misfire Detected
P0301: Cylinder 1 Misfire Detected
P0302: Cylinder 2 Misfire Detected
P0303: Cylinder 3 Misfire Detected
P0304: Cylinder 4 Misfire Detected
P0507: Idle Control System RPM Higher Than Expected

Pending Fault Log
------------------
P0171: System too Lean (Bank 1)

Historic Fault Log
------------------
ECU reports no historic faults
Other discovered fault codes
(possibly pending, current or manufacturer specific)
----------------------------------------------------
ECU reports no other fault codes logged


Thanks!

A large vacuum leak could give you those codes. Check fuel trims.

 

[trandg]

A large vacuum leak could give you those codes. Check fuel trims.

Short term fuel trim is 25%
Long term is 5.5%

 

[mfractal]

Short trim is super high.

Sent from my SM-N9005 using Tapatalk

 

[trandg]

Short trim is super high.

Sent from my SM-N9005 using Tapatalk

Sorry if this is a rookie question, but does the high trim suggest it is a specific problem like the PCV or plugs? Or something else?


Thanks again to everyone chiming in with their input. Im learning!

 

[mfractal]

It basically means you're running lean. There could be tons of explanations to that. What intake are you running Btw? Did you check for vacuum leaks? Pcv?

Sent from my SM-N9005 using Tapatalk

 

[donjuan1jr]

99% it's your pcv.

1% purge valve.

 

[Das Gespenst]

^agreed.

 

[trandg]

Thanks guys. BSH PCV revamp on order. Hoping it fixes stuff. Appreciate everyone's quick help on this!

 

[trandg]

Once I have installed the PCV revamp, should I clear all the engine codes with the VAG COM, or will they clear automatically once everything runs smoothly?

Sorry for the rookie question!