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Rough (ish) engine problem
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Old 26 Mar 2011, 01:06 PM   #1 (permalink)
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Rough (ish) engine problem

Been trying to get this resolved for a while and previously thought it had been sorted, but alas it is still there.
The car is a 2002 WRX 215 with 63k on the clock. No Mods.
Now, the issue is the engine runs slightly rough on idle and also when revs are held higher. The revs hold bet 745 to 755rpm on the scanner at idle and the needle doesnt move. BUT, when the car is held at higher revs on the IACV, the roughness is still there. So, at say 2000rpm, the engine runs rough and as the engine warms up, the rough feeling is still present throughout whilst the revs start to drop. Likewise when the engine is warm (and IACV is not holding revs higher), I can hold it at 2000rpm on the throttle and the roughness is still present. It doesnt make any difference if the car is cold, warm or hot, it still occurs.
It it far more noticable at idle when I can feel the car erratically throbbing and wobbling (only slightly, but it is still there). Whilst holding the steering wheel or door handle, I can feel and see my hand shake!!!

This only happens when the engine is not under load, so as soon as the clutch is engaged the engine seems fine and pulls like a train.
I have done the following:-

Checked, changed and ruled out the MAF.
Fuel filter, spark plugs changed.
Coil packs checked and ruled out.
Running on V-Power for months.
O2 sensor ruled out as symptoms present on cold start when sensor is in closed loop.
ECU reset.

Anyone got any other ideas.
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Old 26 Mar 2011, 11:53 PM   #2 (permalink)
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Re: Rough (ish) engine problem

sounds to me like your camshaft could be out of balance I had a similar problem on an old escort that turned out to be the flywheel had cracked
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Old 27 Mar 2011, 06:17 PM   #3 (permalink)
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Re: Rough (ish) engine problem

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Originally Posted by procomm View Post
sounds to me like your camshaft could be out of balance I had a similar problem on an old escort that turned out to be the flywheel had cracked
I have had a read up on whether it would be a cracked flywheel and it seems that the vibrations would be far worse at higher rpm which in my case it isnt. I think it is going to be something more basic, but cant figure what.
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Old 27 Mar 2011, 07:55 PM   #4 (permalink)
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Re: Rough (ish) engine problem

Neutral position switch?
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Old 28 Mar 2011, 07:18 AM   #5 (permalink)
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Re: Rough (ish) engine problem

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Originally Posted by shambles View Post
Neutral position switch?
Would that cause an erratic idle or just to loose power occasionally?
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Old 31 Mar 2011, 04:26 PM   #6 (permalink)
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Re: Rough (ish) engine problem

I have unplugged the O2 sensor and threw the CEL. I reset the ECU to clear other learned behaviour albeit the CEL was obviously still present. The engine was warm and up to temp as I had just got back from work. The engine runs EXACTLY the same with the same idle issue. No difference in peformance when I drove it round the block.

Does that point to, or rule out the front O2 sensor?
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