Misfiring on Idle

Delta3D · 25 Mar 2018 at 20:23

Hey all,

I've been doing a little bit of work on my friends car (2005 Seat Ibiza 1.2) today to try and fix an issue but it seems it hasn't fixed it.

The issue is that when the car idles for about 5 minutes, it gets the check engine light on the dash and generates a code for cylinder 2 misfiring. Upon turning off the car and starting it back up again the light clears and it runs fine, until it idles again.

Driving is fine, runs like a charm and doesn't miss a beat, whether it's on the motorway or some 30 roads.

What I've tried so far is:

New Spark Plugs
New Ignition Coils
New Fuel Rail & Injectors as of today

I'm stumped as what this could be, I didn't think it would be head gasket as surely it would occur at higher revs too then?

bainbridge · 25 Mar 2018 at 20:27

Throttle body need cleaning?

Delta3D · 25 Mar 2018 at 20:33

bainbridge said:
Throttle body need cleaning?

I had a quick look at it while the engine cover was off (The air filter and stuff is built into the cover so it reveals it when taking this off) and it looked fairly clean - would it be possible for that to cause a misfire in just one cylinder?

Wondering if maybe it could be the valves?

sigma · 25 Mar 2018 at 20:57

Compression test?

Delta3D · 25 Mar 2018 at 21:12

sigma said:
Compression test?

Going to give that a try sometime this week, will post the results.

Iron-man · 26 Mar 2018 at 09:45

Idle speed control valves can make the car sound like its "hunting" giving the impression of a misfire if there all clogged up and sooty.

jpaul · 26 Mar 2018 at 11:03

any air leaks/cracks in rubber booits or engine breather tubes between air filter , air mass monitor, engine ?

wedrum · 26 Mar 2018 at 11:06

get the codes read if any

Delta3D · 26 Mar 2018 at 17:24

wedrum said:
get the codes read if any

Only has the one code for 16686 (Misfire in Cylinder 2) - Used both a little handheld tool and VAGCOM to read it.

Will check Idle Control Valve and other breathers etc when next at the car.

Armageus · 26 Mar 2018 at 17:39

Iron-man said:
Idle speed control valves can make the car sound like its "hunting" giving the impression of a misfire if there all clogged up and sooty.

PCV does this as well (common issue on the bigger vag 2.0TFSI engines)

MatteH Oxford · 27 Mar 2018 at 20:50

You likely have an inlet manifold leak around cylinder 2, spray either some WD40 or some water around that area with the engine running, it'll either rev up (wd40) or slow the idle speed (water) if there is a leak.
What are the fuel trim numbers like via the scan data?