shaking at idle???
02-21-2005, 01:44 PM
#1
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shaking at idle???
I just bought my 02 wrx wagon and absolutely love it, but noticed that the car will shake slightly at idle (very slightly) off and on (every 10 seconds or so). I had the car checked out by a Subaru mechanic and it passed with no problems. Also, the car has never been modified. Is this caused by the boxer motor and normal or is there something wrong with the car?
Thanks
Thanks
Last edited by chrisrex; 02-21-2005 at 01:49 PM.
02-21-2005, 01:53 PM
#2
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First thing that comes to my mind is that you are feeling the engine shake (and ive heard the boxer is known for this) a little due to older/slightly worn motor mounts with the A/C running. (Compressor kicking on about every 10-20 secs.) Is the A/C on when this happens? or does it do it no matter if the A/C is on or not?? Somone else jump in anytime LOL....
02-21-2005, 02:18 PM
#3
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It's normal for the Subaru flat-four. Inline fours, such as those found in most compact cars (other than Subaru), are unbalanced in design and many require the use of tricks such as counter-rotating balance shafts to quell engine vibration. The problem with any balance shaft system is that it takes power to drive it.
The boxer is inherently balanced because the pistons are opposed 180° on the crankshaft. This allows the use of a lighter weight crank with smaller counterweights. I think part of the vibration problem is the result of just having four cylinders so that's not many firing pulses per engine revolution. I'm pretty sure the Subaru flat-six runs much smoother at idle.
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0==WW==0
"…axles of evil…" - george w. bush
The boxer is inherently balanced because the pistons are opposed 180° on the crankshaft. This allows the use of a lighter weight crank with smaller counterweights. I think part of the vibration problem is the result of just having four cylinders so that's not many firing pulses per engine revolution. I'm pretty sure the Subaru flat-six runs much smoother at idle.
--
0==WW==0
"…axles of evil…" - george w. bush
02-21-2005, 02:22 PM
#4
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Car Info: Subaru Impreza WRX 2002
Yes, the "rough idle" of the car is totally normal; the engine idle (when warm) is actually a quite low 750 RPM, and at that speed the little differences in firing time and exhaust pulses add up. I love the roughness of the idle, it reminds me of my dad's 911 Turbo and Carrera (also boxer engines) he had back in the '80s.
02-21-2005, 03:20 PM
#6
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Thanks for the quick responses. The a/c isn't on when it's doing this and the car only has 24,000 miles so I don't think the motor mounts are an issue, but I could be wrong.
You guys are right on with it being a rough idle. It's really not that bad, but definitely noticeable. All that confuses me about this though is that it will idle rough for a few seconds and then stop idling rough repeatedly. I understand the engine would cause this, but how do you explain it changing like that?
You guys are right on with it being a rough idle. It's really not that bad, but definitely noticeable. All that confuses me about this though is that it will idle rough for a few seconds and then stop idling rough repeatedly. I understand the engine would cause this, but how do you explain it changing like that?
02-21-2005, 03:24 PM
#7
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Originally Posted by chrisrex
Thanks for the quick responses. The a/c isn't on when it's doing this and the car only has 24,000 miles so I don't think the motor mounts are an issue, but I could be wrong.
You guys are right on with it being a rough idle. It's really not that bad, but definitely noticeable. All that confuses me about this though is that it will idle rough for a few seconds and then stop idling rough repeatedly. I understand the engine would cause this, but how do you explain it changing like that?
You guys are right on with it being a rough idle. It's really not that bad, but definitely noticeable. All that confuses me about this though is that it will idle rough for a few seconds and then stop idling rough repeatedly. I understand the engine would cause this, but how do you explain it changing like that?
I have the same thing ..mine changes from time to time .. I bought mine new and it only has 15k miles... So I doubt the engine mounts could be the issue but who knows...
02-21-2005, 03:25 PM
#8
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That does sound like the rough idle that results from the a/c compressor kicking in and out. Is your vent control set to one of the two defrost positions with the fan switch 'on'? That'll engage the a/c compressor, also.
--
0==WW==0
"…axles of evil…" - george w. bush
--
0==WW==0
"…axles of evil…" - george w. bush
02-21-2005, 06:03 PM
#11
Originally Posted by meilers
750. Count the lines on the gauge.
Last edited by VIBEELEVEN; 02-21-2005 at 06:08 PM.
02-21-2005, 11:38 PM
#14
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I've checked my A/C-Fan settings and they are all either off or open vents(None of the defrost setings are on).. and still shakes so bad that it feels like as if when a person/pasanger is moving their leg/knee back and forth.. literaly shaking the car...
Does this make sense to anyone?? lol
Does this make sense to anyone?? lol
02-22-2005, 10:22 AM
#15
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Originally Posted by VIBEELEVEN
Is this 750?First line being 0rpm 2nd being 500rpm third being 750rpm(circled) and 4th being 1000rpm ? When I start it warm, it will rev to 1k and then drop dow to the second like before it raises back up to the third. Is this normal?