Hawkeye PPP misfire when hot (no CEL)
 

Hello all,
I've been a long time Scooby owner 2 Impreza's and a turbo forester, but this is my first real problem where I'm stumped...

My Hawkeye has been misfiring quite badly when hot (I live in France now and imported it a few years back).
On long runs it starts misfiring and gets very lumpy, sounding like it's only firing on 3 at best! As soon as things cool down again the next morning, no trace of the misfire and no CEL codes. I noticed a slight leak from the exhaust between the backbox and the centre pipe, but think this may just have been due to the juddering from the misfire.

It's a 56 plate Hawkeye with PPP, walbro fuel pump fitted recently, I just changed the MAF, and new plugs are going in next weekend. I cleaned the K&N air filter after the first misfire incident in case it was over oiled, and am running out of places to look.

Any ideas?

Anyone?

As its a 2.5 might be worth getting a compression test done?

Cheers Scotty,
Am I right in thinking that if the compression on one (or more) of the cylinders was not good, then the symptoms would be there all the time?

Higher temperatures will make it worse IMHO although it may be running "fine" when colder.
I'd do some logging and a compression and leak down test first.

Ringlands went on my 2.0, it was a lot better cold than warm.

Thanks,
Next problem... trying find someone competent in this neck of the woods... =:-\

fpan, were you a Forester owner in the past too? I seem to remember your pseudo from forester.org...

A yes, telemarker, your name rings a bell. yes from sf.org

I'm going to have to ask around at work in Switzerland for a garage that could do me a compression test. The frogs are hopeless and too slap happy, need a bit of Swiss precision (and cost unfortunately!). I have a basic obd2 tool on my blackberry, what sort of logging would show up a ring based fault?

You can buy your own tester pretty cheaply. If you can change plugs you can do a compression test.

Yes I'd thought that might be the case. It's the afterwards bit that's the problem ;-)

Subarus are very popular in Switzerland; I remember even tiny villages in the Alps having a Subaru garage, I guess they are the ideal cars for their weather.

Is there any reason why I'm not getting any CEL codes when it does it?

Had it out today on a 90km round trip, 30C outside, no misfire...

Am I right in thinking that if its the ringland problem, then the oil would be lower than normal and the engine would be smoking (it isn't)?

I'm thinking more along the lines of a coil pack going south personally.

Depends where the ringland has failed. The oil control ring was in one piece on mine and it wasn't blazing through oil.

This is what mine looked like when it came out of the bore:

Attachment 45531

Then with all the bits removed:

Attachment 45532

That was the worst piston, another had also cracked.

Yikes... I've just lost my appetite ;-)
I've found a garage who does Impreza rebuilds and tuning a couple of hours away so if the worst comes to the worst I now know where to go!

I'd just compression test it for piece of mind and go from there.

The Impreza is in for new plugs, coils, and a compression test... fingers crossed!

Hope it doesn't turn out too expensive for you.

Thanks! I've found a garage about 3hours from here that has a good reputation for builds on Impreza, just hoping I won't have to use them!

Well, the verdict is in... two dead plugs, compression ok. Hugh sigh of relief!

Easy cheap fix then!

Yup! Any ideas on why one side of the engine has eaten the plugs? I'm hoping that the change of coils will stop that from happening again.