Resolved: Multiple cylinder misfires

J

Joefreegard

Member
:) Hello all,

So as described my z4 3.0 2004 is misfiring on cylinders 1,2,3 and 4. It’s done 93k

About 6 months ago it started dipping in revs at idle, which I thought was odd.

A month or so after that the amber engine warning light came on.

I took it in to a garage about 6 months after that to have to codes pulled. (I know I should have done it sooner) and it was reading misfires on cylinders 1,2,3,4 I had them reset and the plugs changed.

Still getting the dip in revs at idle and the light came back on about a week later. I’ve taken it back in and it’s still misfireing on the same cylinders. I’m thinking of changing the ignition coils but it’s a lot to fork out if that’s not the problem. Seems odd that they’d all be playing up right?


There were other fault codes apparently related to the misfiring. Some sensors. 02 I think.

I’ve just tested all the coils with a multimeter. They were all 1.0-1.1

It still runs fine, the erratic idle hasn’t ever worsened but I’m unfortunately putting it up for sale so I want to get rid of the engine light.
 
Misfiring on hard acceleration is likely to be coil packs and yes, you often find a few going in quick succession of each other. If after you have replaced all 6 (don’t just do the suspect ones) and have erratic idle it will either be o2 sensor or split in the elbow on the intake.
 
ph001 said:
Misfiring on hard acceleration is likely to be coil packs. It’s fine when driving hard acceleration or not, it’s just when it idles, the needle bobs up and down a bit. I’m just not conviced it’s the coils, it’s such a subtle change in engine beat, for 4 coils to be gone surely it would be more obvious?

Update: I was just having a look at the intake system to check for any splits that could be making the mix too lean. I gave the elbow on the intake a look, it seems fine.

Any way, I took the DISA valve off, mainly to give the idle control valve a clean, and the spindle to the flutter valve has snapped. I think that may be the culprit? I just googled the thing and apparently it’s a common part to fail.

The idle control was clogged too, it was barely able to move.
Click to expand...
 
ATTACH]


Fooked
 
DISA valve probs don’t normally result in a misfire afaik but its a common failure point certainly.
 
Oh ok, I was hoping that would be the problem solved!

I’m hoping it’s a vacuum problem, or something reasonably simple. Could it be a poor seal around the DISA? The O ring looked like it wasnt doing a lot.

I’ve ordered a rebuild kit anyway, if it solves the problem I’ll be sure to post for other people’s reference.
 
That does look in a bad way. Hope those bits of plastic that seem to have broken off havent gone into the intake.
 
Well, tbh I’m not sure where else they could have gone ha. I laugh but it’s not really funny is it.

I’m hoping as it would just have been small bits of plastic they would have just been chewed up and spat out? Probably a little optimistic.
 
Looking again at that broken plastic, it looks fairly recent and not sure how it could have happened. Before fitting rebuilt unit I would have a good look inside the intake housing to make sure they are not still inside there. For instance I recall that the pin sits inside a recess.
Good luck and let us know how you get on.
 
I had a look as best I could when it was off last time.

I think it’s been this way for a while as I’ve been hearing rattling coming from there, didn’t know what it was before. I have the metal pin, which is a relief.
 
Update: rebuilt the DISA today, the new O-ring seems to be doing the job. It really took some work to get the DISA back on with the new seal, where as before it just kind fell in and out.

The engine idles smooth as silk, where as before it was a bit up and down with occasional judder, it also feels a lot more torquey with the DOSA doing its job.

Engine light is still on, I would have though it would turn of now the misfire has gone? I have a scanner arriving Monday (was supposed to be here today ☹️) so hopefully with a reset all will be back to normal. I let you all know.
 
Yeah! Always a relive with these engines. My last car was a jeep V8 and if anything went slightly wrong it was a grand at least. America crap.
 
Just for peoples reference in the future, the codes have been cleared and engine light reset, it’s not coming back on or throwing any more codes. Must have been misfiring due to a vac leak on the DISA valve.

So, glad I didn’t just blindly change the ignition coils at the cost of £200ish like the mechanic said.
 
You must log in or register to reply here.
Back
Top Bottom