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Old 03-07-2008, 11:18 AM   #1
gtfaded
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Default Help- engine stumble

I'm going to try and explain this as best as possible. For about a week now my rpm guage has been "jumping" at about 3700. When i give gas while at 3700 rpm the tach jumps up to about 4200 then holds there for a moment then falls about 300 rpm then jumps back up about 500 rpm, it likes to do this most in 4th and 5th gear but i have had it do it in 3rd as well. However while the rpm tach is jumping u can also hear the fluxuation in the engine but the speed consistantly increases, it's like you can hear the motor get the gas hard first then it bogs or stumbles then recieves the fuel again. This has me stummped, it seems it could be the turbo, fuel pump, injectors,... and i have no cel. Any help is very appreciated.
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Old 03-07-2008, 12:00 PM   #2
Subie Gal
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sounds like a failing 02 sensor

sensor can begin to fail, no cel, and your idle will fluctuate like mad
car wont run well and it will only get much worse before you have a cel

also,
what mods to you have?

anything added recently?

Jamie
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Old 03-07-2008, 12:05 PM   #3
gtfaded
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right,...mods. Vishnu reflached ecu, ive had for about a year now along w/ the rest of the mods. 3inch borla hush exhaust, 2 1/2 inch upipe, drop in k&n filter, ground system. The car idles fine, I get a cel every now and then i think is from the exhaust but never had it affect performance, however i will deffinatly be priceing o2 censors now. Any other thoughts?

Last edited by gtfaded; 03-07-2008 at 01:29 PM.
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Old 03-07-2008, 05:55 PM   #4
gtfaded
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perhaps an exhaust leak, maybe keeping the turbo from spooling consistant,or would i hear that?
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Old 03-08-2008, 10:59 AM   #5
Subie Gal
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you'd hear an exhaust leak.

seeing that you have a K&N filter
it may be a good idea to inspect your MAF sensor as well

oil from the K&N has been known to destroy MAF sensors.

OEM filter really is best for our cars....

Jamie
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Old 03-08-2008, 11:22 AM   #6
gtfaded
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so if the oil has come in contact w/ the MAF i would need to replace or would i be able to see or tell if it had oil on it and could clean it off? i've removed the filter and cleaned it twice already. however it really does seem like it would be a sensor, it's just acting to strange i drove it to work this morning and seems to be worse, it did the same thing 1000 rpm sooner than it had been. i'm sure i'll just have to get under there and start checking and replacing thing's but thanx for giving me a place to start. i'll keep this updated if i find out anything new, and please feel free to list any other problems u believe it to be.

Last edited by gtfaded; 03-08-2008 at 11:45 AM.
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Old 03-08-2008, 11:29 AM   #7
Subie Gal
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you could try cleaning the maf,
but 99% of the time, it needs to be replaced

hard to say what is causing your issues

I'm just tossing out some ideas based on personal experience.


again, 02 sensor, as it worsens, the car will worsen.


another thought
spark plugs.

when were they last changed?

perhaps pull and inspect them.

Jamie
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Old 03-08-2008, 02:39 PM   #8
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I had this issue on an old car of mine. At a certain point the tach would jump around. It ended up being a bad control module. One way to check. Does it do it if you are at a stand still? If yes have someone rev the engine until it happens. Place your hand at the tail pipe and feel the exhaust. It should be a constant feel from the cylinders. If you have a miss you should be able to feel it. If you have any questions let me know.
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Old 03-08-2008, 03:46 PM   #9
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i have reved it while sitting in neutral, it hasn't happend while doing that so far. the problem occurs consistantly from 3000 to 4000 rpm. after giving it gas it takes a sec then u can hear the engine rev, then it revs very fast, abnormally fast, almost likes it's catching up to itself, then when it does catch up (usually about 1000 rpm ) it stops, drops a few hundred rpm, then begins to rev again. its freakin me out, it's a depressing situation all together.
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Old 03-09-2008, 12:42 PM   #10
Subie Gal
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Quote:
Originally Posted by gtfaded View Post
i have reved it while sitting in neutral, it hasn't happend while doing that so far. the problem occurs consistantly from 3000 to 4000 rpm. after giving it gas it takes a sec then u can hear the engine rev, then it revs very fast, abnormally fast, almost likes it's catching up to itself, then when it does catch up (usually about 1000 rpm ) it stops, drops a few hundred rpm, then begins to rev again. its freakin me out, it's a depressing situation all together.
wait a minute.

you mean you are fine until you're on it, throttle hard around 3-4k
and the engine SLIPS a bit, revs shoot up?

then, you back off of the throttle and the revs come back down a bit?

something like that?

is this car a manual transmission?


Jamie
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Old 03-09-2008, 01:00 PM   #11
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^^^ thinking a slipping clutch like I am.
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Old 03-09-2008, 01:27 PM   #12
Subie Gal
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Quote:
Originally Posted by flstffxe View Post
^^^ thinking a slipping clutch like I am.
yeah... definitely.

sounds like the clutch is gone/going....

Jamie
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Old 03-11-2008, 11:49 AM   #13
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Gotta give ya'll credit, it's deffinatly tha clutch. figured it out sat night. i knew it was bad but man,...well i'll pricing one those now. theres a shop here that rebuilds them, can even go w/ stonger springs and different material, my next mods will probably be a turbo along w/ injectors bigger tmic and meth injection. would you all recomend the rebuild or a whole new clutch, like from act or exedy?
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Old 03-12-2008, 10:56 AM   #14
Subie Gal
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I recommend:
Put in a brand new clutch. Flywheel and all

If you have no power mods, OE clutch is Exedy made and will do you fine.


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Old 03-12-2008, 12:02 PM   #15
gtfaded
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thanx,... OE? as in organic, do u think semi metallic will damage something?

Last edited by gtfaded; 03-15-2008 at 12:40 PM.
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