R56 Cylinder 4 misfire after fuel filter change
Cylinder 4 misfire after fuel filter change
Hey guys,
(Edited 11/19/16 - Problem has been solved - it was simply a matter of old spark plugs.)
So for a while now I've been having a stutter under load from my 2008 R56S N14. All stock, 110k miles. At first it was at WOT only, I'd get a little blip of power loss and then everything would be normal, happened maybe once a day. Recently it has worsened, and under even moderate acceleration it stutters and struggles, and generally seems very unhappy about the whole situation. Never threw a CEL, though.
I thought it felt like it might be a fuel supply issue, so I went ahead and replaced the fuel filter this weekend. The filter was good 'n dirty, so it was worth doing either way. Took it out for a test drive and under gentle driving it feels fine. However, when I give it a bit of gas, it stutters and starts seriously misfiring in cylinder 4, throwing a CEL and the code P0304.
I'm not really sure where to go from here - has anyone had a similar experience and (hopefully) been able to diagnose and fix it?
(Edited 11/19/16 - Problem has been solved - it was simply a matter of old spark plugs.)
So for a while now I've been having a stutter under load from my 2008 R56S N14. All stock, 110k miles. At first it was at WOT only, I'd get a little blip of power loss and then everything would be normal, happened maybe once a day. Recently it has worsened, and under even moderate acceleration it stutters and struggles, and generally seems very unhappy about the whole situation. Never threw a CEL, though.
I thought it felt like it might be a fuel supply issue, so I went ahead and replaced the fuel filter this weekend. The filter was good 'n dirty, so it was worth doing either way. Took it out for a test drive and under gentle driving it feels fine. However, when I give it a bit of gas, it stutters and starts seriously misfiring in cylinder 4, throwing a CEL and the code P0304.
I'm not really sure where to go from here - has anyone had a similar experience and (hopefully) been able to diagnose and fix it?
Last edited by embiggenedmini; Nov 19, 2016 at 02:11 PM. Reason: Adding solution to the problem
Do some visual inspection, like moving the coil pack on # 4 to lets say #1. take the spark plug out and see the shape of it (the gap). you can also do an injector swap to see if that moves the CEL. these cost about $5 (a COC {Cup Of Coffee} 
). While the intake is out, shine some light on the valves and see what is next to do 
). While the intake is out, shine some light on the valves and see what is next to do
Funny you should mention that. I did a walnut blasting of the intake valves last year, around 90k miles. Looked like the first time it had ever been done, they were filthy.
This stutter doesn't feel the same as the superknock from fouled valves. Most obviously, there's no puff of black smoke out the tailpipe this time. Also, it wasn't this bad even after 90k miles of buildup; I'm doubtful it would have gotten so bad in just 20k miles.
If there are no other suggestions, I'll pull the manifold and take a peek at the valves though.
This stutter doesn't feel the same as the superknock from fouled valves. Most obviously, there's no puff of black smoke out the tailpipe this time. Also, it wasn't this bad even after 90k miles of buildup; I'm doubtful it would have gotten so bad in just 20k miles.
If there are no other suggestions, I'll pull the manifold and take a peek at the valves though.
Problem Solved
Did some systematic testing - first I switched the #4 and #3 coils: no change, still misfire on #4 (P0304). Next I switched the #4 and #3 spark plugs, and, sure enough - misfire on #3(P0303)
$40 later, new NGK plugs and it's running beautifully.
Thanks everyone for your help and suggestions.
$40 later, new NGK plugs and it's running beautifully.
Thanks everyone for your help and suggestions.