05 GT misfire

[PominaSube]

Car is a 2005 Liberty GT and generally runs fine - starts, idles, spins to redline, strong boost, reasonable (for a turbo flat-4) fuel economy - nothing untoward. Except, it has an annoying misfire in the mid-range - its not a full-on, nose-to-the-windscreen type of miss, more a jerkiness as the revs rise. Doesn't do it all the time, but is frequent enough to notice on most journeys. Most noticeable around 2000-4500rpm, can be on light throttle or foot-to-the-floor. Don't usually notice it above about 4500rpm - which does lead to one obvious solution...

So far I've replace plugs, coils, MAF, fuel filter and air filter - what next?? Car is always run on 98-RON - either Shell or BP.

Its really bugging me, as its the only thing marring the bonding that's going on

[chubbs]

I had a similar issue not long ago i replaced my spark plugs and it solved my problem. are you running stock fuel pump? are you sure its mechanical issue? stock or tuned?

[JMlegacy]

Car is a 2005 Liberty GT and generally runs fine - starts, idles, spins to redline, strong boost, reasonable (for a turbo flat-4) fuel economy - nothing untoward. Except, it has an annoying misfire in the mid-range - its not a full-on, nose-to-the-windscreen type of miss, more a jerkiness as the revs rise. Doesn't do it all the time, but is frequent enough to notice on most journeys. Most noticeable around 2000-4500rpm, can be on light throttle or foot-to-the-floor. Don't usually notice it above about 4500rpm - which does lead to one obvious solution...

So far I've replace plugs, coils, MAF, fuel filter and air filter - what next?? Car is always run on 98-RON - either Shell or BP.

Its really bugging me, as its the only thing marring the bonding that's going on

Mine is doing this right now too. I hear it when i come on to boost. Once i'm on boost it is fine.
Do u have any modifications? I'm running an STI turbo with 1 step colder plugs.

When u find out be sure to message me.
Things that have cause me misfires in the past:
plugs
coils
cam sensor
crank timing gear

[PominaSube]

As far as I can see the whole car is standard - no mods at all. I'd like to get it running properly before thinking about anything (and there's the small issue of cash to consider...)

Plugs have been changed, and the old ones looked like worn spark plugs - no signs of any untoward running probs. So too all four coil packs. It runs better since replacing those items, but its not completely cured.

I'm not convinced its mechanical, my spidey senses tell me its electrical - perhaps earthing or some such - but its only a hunch. It could well be a hole in a hose somewhere. Will need to get it on a proper diagnostics machine I reckon, though its not throwing a fault code. Any recommendations in the Sydney area...???

[jslayz]

knocking on spool.....just a theory....

j

[dr20t]

2000-4500 is right in the peak torque area of the stock ej20y (or x)

This tells me its boost related (which could be fuel/ ignition [knock as jslayz pointed out above] or mechanical on the induction side of things, all whilst on boost).

Best bet is to get in touch with a forum member having access to a Tactrix cable and laptop to do a learning view for you. I'm happy to assist if need be just let me know and ill try and help

Mick

[PominaSube]

2000-4500 is right in the peak torque area of the stock ej20y (or x)

This tells me its boost related (which could be fuel/ ignition [knock as jslayz pointed out above] or mechanical on the induction side of things, all whilst on boost).

Best bet is to get in touch with a forum member having access to a Tactrix cable and laptop to do a learning view for you. I'm happy to assist if need be just let me know and ill try and help

Mick

Thanks - might take you up on that offer. Don't mind paying to put it right, but not willing to pay for others to test their guesses!

[Sean82]

Best bet is to get in touch with a forum member having access to a Tactrix cable and laptop to do a learning view for you. I'm happy to assist if need be just let me know and ill try and help

Mick

^^THIS!
I had a "stall" issue not long ago that I thought my be the box (clutches in the auto no disengaging properly). Finally plugged the Tactrix in and found the inlet cam on the right bank was stuck at 50* of advance. Took the solenoid out and there was junk in it.

Good luck with the search for the issue

[PominaSube]

Thought I'd post an update on this. Car needed a rego check, and was time for an oil change, so feeling lazy, I booked it in for rego and once-over service at a local Subaru independent. I've used them before and they've been competent, so knew I wasn't passing the car to numpties. Also asked them to plug the car in and see what they could find. When I talked about the symptoms, and mentioned I'd already changed plugs and coils, the owner started thinking about CAS or O2 sensors.

Anyway, I catch a bus to work and they plug it into whatever laptop kit they've got and take it for a spin. I get a call later saying they can't find any sign of a misfire, and doesn't it go well! I ask they've called the right guy about the right car and, yes, its my car they're talking about. They duly put it through rego, give it a once over and sump of fresh oil, and go out again, just to check. Computer says "No!" There are no fault codes and no sign of any miss, all sensors working within range. This time, when he calls back, he's comparing it to an STI they had in the day before, and noting that mine seems more-responsive and quicker, pulling well from about 1500rpm and spinning freely to the redline. I tell him he's bluffing.

Now, I've just taken it out for a good thrape and, y'know what, that miss really has gone, and it really does move well. It is possible for me to get it to feel like its hesitating slightly, but its barely detectable, and limited to a very small band of the rev range. In short, something has happened, and I'm not sure what but the car is eminently more fun. Would the mere act of plugging it into the computer to look for problems have reset anything? Of course, karma is a bitch and will bite me on the arse for posting this, but for the moment all is fine. I just don't know why. Not helpful, but thought I'd let you all know!

[Heywood Jablowme]

Find out if they did a ECU memory clear prior to driving it.

Could be something the ECU has learnt over time, but the ECU memory clear has reset it to base settings.

So an example is that ECU's are very quick to learn poor fuel, but slow to learn good fuel, so a memory clear can assist under some conditions...

Did you happen to notice the issue driving it there?? Also surprised they didn't go for a drive with you so you could demonstrate your concern...

[PominaSube]

Didn't think I'd need to point out the problem - it was that obvious, so no need to go with them for a test drive. No idea if the ECU was cleared, but still running well! Am tempted to think it might be a recent thrashing that helped things along - proper Italian tune-up stuff - plenty of time over 5000 rpm. Anyway, if it changes I'll start trying something else, just not sure what