intermitent missfire

[Caldweld]

HI lads very new to the forum been reading for a while but only just signed up!

The issue,

I have had the lib for almost a year now and about a month ago it stalled (auto) at the lights after running very rough for a few seconds while i was braking.
Didn't hear from it again for at least another month when it did it twice in one day this time i managed to catch it with a little throttle and it didn't stall car proceeded to run perfect again for about a week, thats when the trouble got worse.

on cruise control 60kph very slight up hill the car started to miss(run rough) the computer kicked down a gear and it cleared, then again 10 minutes later very erratic.

Replaced plugs, upper engine clean, injector clean and left battery disconnected for a few hours miss didn't clear but my fuel econ has been a bit better. this miss is driving me nuts it is so intermittent and at low rpm, low load, very low throttle

Happens more often after cruising for 5 minutes at constant speed but then it can also happen just after accelerating from a set of lights and stopping for next set. every time i have tried to reproduce it i have failed and the car hasn't missed a beat.

I guess im just wondering if anyone knows if the 02 sensor could be causing this or something else that is random and we haven't checked

Cheers - Terrence.

[Dropz]

Check the plug leads for correct continuity or corroded connections, etc.

[Caldweld]

They have done 150k so i'll replace them, anything else though? leads i have always been told are more a of a load issue yet my missfire happens mostly on decel or cruise.

[Dropz]

o2 sensor or knock sensor are both common issues.

[AlpineRaven]

I would also check MAF sensor as well. (Yes O2 & MAP sensor as well)
Is the timing belt in correct position?
Cheers
AP

[Caldweld]

Ok thanks i'll take all that under advisement

I have no check engine light does that matter for the 02 maf or map?
would a normal scan tool pick these up? or is this a crack out the credit card and go to subaru
i can line the motor up on TDC and check the timing marks

[jslayz]

Have you done leads yet, sounds like a prob I had on my old turbo 13b rotary, leads were stuffed then and it started to have an intermittent rough running issue.

Good luck tracking and fixing, these intermittent issues are a PIA!!

J

[bass_straitener]

G'day Terrence,

Which state are you posting from. Perhaps someone local could check your car via a scanner and see if any DTC have been recorded previously for any sensors.

This sounds most likely to be an outgoing sensor.

Or plugs and maybe leads.

Whilst you may not see and CEL a code will be recorded in your ECU. See if someone can help you locally.

Or ring Subaru and see if they're prepared to check it for you for free or your local mechanic.

[Dropz]

It's possible for a sensor to be faulty without logging a code, especially when it is intermittent.

[AlpineRaven]

It's possible for a sensor to be faulty without logging a code, especially when it is intermittent.

That does happen.
Cheers
AP

[Caldweld]

Wow thanks for more advice!
I live in Hawthorn/Melbourne, i have a work shop that are willing to help me out a little.

just today the miss started happening more frequently, also a new symptom Sluggish from standing still to 10kph then takes off, all other conditions the car drives like a dream!

Accelerate from the lights, reach speed and coast, as i release the throttle the revs drop to well under 1k and then pick back up to 1.5k while in decel and at the lights it will be shaking around and idling at 500 if not less untill i tap the throttle and it picks back up to just under the 1k mark.

I think I noticed it happened more often if i drove a bit harder but that might be placebo, because as again i tried to reproduce it at the next lights and nothing not a hicup happened atleast 8 times today I drove from camberwell to millpark (about 45 minutes eachway lots of stop start traffic)

[Caldweld]

replaced leads no change

Next is a scan next week i hope