Engine running rough - coil replaced but not fixed

[Newyorkmikey]

Feels like my 2003 Z4 2.5i is having a laundry list of issues at the moment!

The latest - the car sat for two weeks without being used. Started it up and it ran really rough, after a minute or so the check engine emissions light came on. Restarted and it seemed fine, but it was missing a little at idle.

Took it into the dealer here and they hooked it up to the computer and diagnosed intermittent misfires on coil 5. Replaced the coil pack and I drove it home.

It didn't go anywhere for a few days again, started it up this morning and it sounded rough again. Basically chugging and spluttering a little. I didn't wait for the check engine light to turn on, but instead restarted, and this time it sounded fine (no misfires that I could feel or see in the RPM needle vibration).

The guy at the garage said if the coil pack didn't fix it, the next step was to replace the lifters (four under that coil), an $800 AUD/ 400 GBP job due mainly to the labour involved.

I'd appreciate any experiences in this area, I'd like to make sure I'm informed when I'm talking with the garage. If the price seems steep, I'll go to my local indy for a quote too.

Also, whether I should just get them to replace all 24 lifters while they're in there if the labour wouldn't be much greater?

Thanks in advance,

Mike

 

[EdButler]

Hmm, id very much doubt it was the lifters mate - theyd emit a loud top end 'tapping' noise if they were on their way out. Id strongly favour a bad injector over a bad lifter... but ofcourse that would get the garage less labour money

To be honest, try just taking it out for a long run and a good "Italian Tuneup..." This used to happen all the time to the VX220 lot due to 'water ingress.' Basically electronics (Spark or Injectors) get damp from being exposed. Could also be water in the fuel, try some fresh high octane stuff...

To check the lifters - do a simple compression test. Testers are cheap and you probably know someone with one Use the "How To" guide on this forum (By Shipkiller iirc?) to take all coils out and remove all spark plugs. Then wind the tester into each cylinder, open the Throttlebody and crank the engine about 6 times over. Record and make sure all cylinder readings are between 10% of each other.

While theyre out, check spark plugs to make sure Cyl5 is indeed at fault! The Plugs should be a light brown colour... Black = Oil/Rich and White = Lean

Best way to test injector firing order is to remove the wiring harness and literally place a bulb there instead on the electrical contacts - lets you know that the injector is recieveing a correct signal.

To check a dodgy injector is quite hard itself. You could try checking it fires into an enclosed container but id personally try switching them over with another cylinder to see if the fault code changes.

 

[srhutch]

As EdButler said if it was lifters you would have a tappety noise from the engine, and dont thing it would idle roughly either mine certainly didnt with lifter issues.

I have read the chaning all the coil packs in one go is best as you could be forever chasing your tail.

 

[Newyorkmikey]

Just a quick update in case anyone has similar issues.

Took it out for a long drive at the weekend (Italian tune up and all that - 4th gear down the highway to keep the revs up for a while). And so far so good, no repeat of the tractor style chugging.

Thanks for the detailed input and suggestions - I'm going to take it out again this weekend to see if it's still running well. I'll update again if I have any further problems.