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Old 12-23-2003, 01:08 AM   #1
MaddMax
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Member#: 9264
Join Date: Aug 2001
Location: Kansas City
Vehicle:
2012 WRX 5dr
Ice Silver

OMGHi2U Odd engine stumble/vibration from 1900-2500rpms in neutral

On my wife's 98 Legacy GT 4EAT (78K miles) I've noticed a very strange engine stumble/vibration problem if the car is held at a steady rev anywhere from 1900-2500rpms in neutral/park. The stumble/vibration seems worse around 2300rpms. I can also hear a faint metallic noise when this is occuring The problem disappears the second the rpms go past 2500rpms. Anyone have any clues? Needless to say this car makes me a bit worried. This weekend I plan to:

1) Check the coil pack
2) Check the plugs
3) Check the O2 sensors
4) Check the plug wires
5) Adjust the band clearance so the 2-3 shift isn't as slow
6) Do a little house cleaning in the throttle body and general whip down of the motor.
7) Replace the burnt out HVAC lights
8) Check a few solenoids to see if they're causing the infamous torque bind (doubt it).



Dave
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Old 12-23-2003, 03:40 AM   #2
THAWA
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the metallic noise could be your exhaust heat shield(s)
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Old 12-23-2003, 09:05 AM   #3
sha_zapple
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Quote:
Originally posted by THAWA
the metallic noise could be your exhaust heat shield(s)
My moms Outback gets rocks in hers all the time! So annoying!
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Old 12-23-2003, 10:13 AM   #4
sooberoo
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Seeing you will have your head under the hood ,you should try the ground mod. Do a search and you'll find it. My car ran a lot smoother after doing it!
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Old 12-23-2003, 10:33 AM   #5
Subietonic
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Items 1-4 on your check off list will go a long way toward zeroing in on the root cause which, if air and fuel delivery are all good, is more than likely going to be your coil pack/plug wires (I've had to replace both on my two 98 GTs (4EAT and 5MT)). First check I'd do is to pull the plug wires off of the coil pack and if you've got corrosion there, then more than likely, you've got a coil pack that is partially firing and causing the intermittent "stumble" that you describe. If you have an OBD-II reader, you can also check for misfire in one or more of your cylinders. If you have that I'd start with the coil pack, then the plug wires, then the individual plugs themselves. The metallic sound you're hearing could be misfire detonation/"ping" or, as was mentioned, the heat shields could be loose on your exhaust system and are effected by the harmonic/vibration created at that RPM/load speed. Good luck and keep us posted. Also agree with the ground mod. Done this to all five and WOW, what a difference in smoothness and overall operation, particularly on the 4EATs.

Br, Dale
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Old 12-23-2003, 10:53 AM   #6
MannySoobia
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Yeah I noticed lately that when I start up "THA RIDE", that sometimes, I get this thing where the Idle will fall really low, then, there's compensation for it and the engine will rev higher than usual. It'll go thru this a few times until it finally finds the "sweet spot". Is this something like what's goin on for -MaddMax??

One thing I do know is,..... This had NEVER happened until I had all the EGR componants installed as of lately,......so I could smog my JDM Transplant. Anyone have any Ideas??

-- Manny S.
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Old 12-23-2003, 10:59 AM   #7
Subietonic
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In the case of the dropping/rebounding idle, I'd check both the throttle body and the idle air sensor (IAS) located just below and to the left of the throttle body (looking toward the firewall from the top of the throttle body). I wrote up two, long posts on how to check/fix both of these. If you do a search on my screen name for "throttle body" and "idle air", they should pop right up.

Br, Dale
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Old 12-23-2003, 01:54 PM   #8
MaddMax
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Thanks guys. I'll do a full blown check of all the systems you noted and I'll probably clean up all the grounds too. I'll keep you posted on what I find out.


Dave
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Old 12-23-2003, 05:02 PM   #9
MaddMax
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Does anyone know of a good way to test plug wires other than inspecting them? Or should I just buy replacements since the car is over 5 years old? If I should replace them, can anyone give me an idea of spark plug wire cost and a good place to get them? I've tried doing a search and I'm not turning up much other than "Magnacore wires" which I don't want to buy due to potential seating problems.

www.subaruwrxparts.com lists a set of OEM plug wires for a 98 Imprezza RS for $55. Wouldn't these wires work on my 98 Legacy GT since it's the same exact engine and coil?

Thanks,


Dave
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Old 12-24-2003, 01:10 AM   #10
Subietonic
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Try 1ST Subaru Parts. You're looking at about $12.00 each wire (you'll need two #1 and a #2 and a #4) and if I do the math correctly, that's about $48.00 vs. the $55 at subaruWRXparts.com. The wires are all in stock at this time.

For diagnostic assessment of the coil pack, crank and camshaft position sensor and plug wires, check out this Subaru Endwrench Article

Br, Dale
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Old 12-24-2003, 01:19 AM   #11
subiekid
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could check IAC valve.

too lazy to read entire post.
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Old 12-24-2003, 02:19 PM   #12
MaddMax
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Ice Silver

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Quote:
Originally posted by Subietonic
Try 1ST Subaru Parts. You're looking at about $12.00 each wire (you'll need two #1 and a #2 and a #4) and if I do the math correctly, that's about $48.00 vs. the $55 at subaruWRXparts.com. The wires are all in stock at this time.

For diagnostic assessment of the coil pack, crank and camshaft position sensor and plug wires, check out this Subaru Endwrench Article

Br, Dale
WOW, thanks a bunch.


Dave
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Old 03-26-2004, 09:48 AM   #13
White2.5GT
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I know it's an older thread, but I used a wire brush to clean some of the deposits of my coil pack today and it fixed the stumbling I had at the same 1900-2500 rpms.

if anyone is having this problem give it a try...if it keeps coming back I'm getting the coil pack checked and replaced...but for now the car is much smoother and happier!
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Old 10-12-2004, 07:23 PM   #14
White2.5GT
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stumble came back so I ordered some new wires...they are due anyways, they have been on the car since she rolled off the line 7 years ago.
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