Thought i'd add to this thread rather than start a new one seeing as this is a similar issue i'm having in my 01. I'm getting misfire under load, more so when off-boost. It seems to be ok when it's cold but after a few mins of driving it will all of a sudden change into 'misfiring mode'. The car shakes quite a lot while idling once it starts misbehaving. I've changed the spark plugs and cleaned off the AFM but no luck. Guess just take everyone's advice and start looking at swapping out leads, coilpacks and the AFM?

Anyone got a spare AFM lying around that i could try testing? :O

Thanks.

Replaced the AFM and thought it was all ok but today it started playing up again... Not having much luck at the moment :S Can anyone recommended a good place to fix an intermittent fault like this? If it comes to that...

I got misfiring also, turns out to be ignition problem on cylinder 1. I currently have the injector disconnected and so am putting around on 3 cylinders. Is this wise?

I would like your opinion on what I need to replace and in which order to determine the issue. I suspect at this stage it could be the following:

a) coil pack
b) leads
c) spark plug
d) other

The misfiring initially was just noticeable, but has gotten worse. I opened the bonnet under idle and it was arcing through the distributor coil pack to the bolt holding the pack to the manifold.

When I got home, I pulled it part and took the following photos. Notice the corroded terminal for cylinder number 1. The spark plugs seem fine, the left was from cylinder 3 which is working fine, and the right is from cylinder 1. If anything, it's a bit dark, but I suspect because it hasn't been burning the fuel properly (ie over fueled and rich).





When I put everything back together, it ran smoothly without the misfire. But today after a bit more driving the misfiring occurred again.

Where can I get leads and coil pack?

Cheers,
Fred
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Step one: Clean all that corrosion off.
Spark is electricity. It will find the "path of least resistance"... If that happens to be through the air and to the bolt on the coil pack (an earth), then it will.

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Thanks for the input. I suspect that would only be a temporary solution and not the cause of my misfiring. I'm curious as to why only one terminal has the corrosion. I'm certain if clean it up, it's going to come back by some sort of galvanic corrosion.
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I had the same problem in my Liberty, with misfiring when i accelerated. It was only one terminal that was corroded, it was sparking off the bolt that holds the coil pack. I replaced all four lead, instead of just one cause thought if one was on the way out the others might be aswell. After I replaced them had no further problems.

some decent iridium/platinum plugs wouldn't go astray also

Replaced all plugs and leads, sanded the corroded terminal to expose some shiny stuff.

Didn't buy expensive plugs as this is only an impreza rx :P

Let's see how long this last before the misfiring comes back.

Cheers,
Fred
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CandyDirty cam

At the risk of a flaming, i also hav misfire trouble. First step was to check plugs, what do you know number 4 plug was hanging in by two threads, ok replaced plugs.. Still no joy, ok replace leads with bosche motorsport leads(not cheap!) still misfiring, change out o2 sensor with bosche direct fit, still misfiring. Starting to get shitty about it now. Car is my99 wrx, tbe, 16 psi on stock computer and 230000 k's.
My question is, is it likely for the coil pack to hav died on the cyl with the misfire, or could i have damaged a valve/injector?
Or do i have to clear an error code after fitting new plugs, leads and o2 sensor?

Cheers guys, any help would be great!

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