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Old 04-10-2005, 05:56 PM   #1
Keith
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Default surging when letting off the throttle?

When I let off the gas while in gear, the car surges. (almost like i'm hitting the gas a bit then taking my foot off).
for example, if I'm in first gear rolling through a parking lot (no gas), the car will start to buck as if I was some noob 5speed driver.
Weird thing is that it only starts after I have been driving the car for a while. Today I was driving for about 10 mins, then it started.

Another thing, If I throw it in netural and just watch the tac, I can watch the needle jump. If i put my heat on, it doesn't do it as bad. Again,this only happens after a few mins.

That is new. Normally when I take my heat off the car will start to idle at like 1500 rpms-2300 rpms.

93 impreza L with 02wrx swap.
was fwd auto, now 5speed manual. Harness was done by someone with expereince.
Another thing, may be unrelated, after a few mins I can't get past 4.5k-5k rpms without the car hitting fuel cut. Boost is normal (not over boosting).
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Old 04-11-2005, 10:06 AM   #2
Keith
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ideas? There is a high likely hood of me burning this car.
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Old 04-11-2005, 01:50 PM   #3
burrito007
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it just happens with the older wrx ecus i think... maybe a reflash will help? it helped my 04
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Old 04-11-2005, 03:44 PM   #4
Keith
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no, i don't think it was the same thing that I got on my 02 wrx before. I'm talking about serious surging..not just the "blank spot" that happens inbetween 3-4k rpms.
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Old 04-12-2005, 10:31 AM   #5
Diz
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IAC solonoid or TPS? I'm not 100% sure of this, though. If you had a bad solonoid or sensor, I would expect the car to throw a CEL. Good luck finding the problem.
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Old 04-15-2005, 04:31 PM   #6
DiscoGsus
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Assuming its not just the compressor surging. i.e.. you build up some boost and totally let off the throttle, it closes the throttle plate but the compressed air from the turbo literally forces the throttle plate open, giving you a little surge.

Sounds like an electrical gremlin thats messing with you.
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Old 04-15-2005, 06:22 PM   #7
dentprone
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i recently swapped an 02 wrx engine into my 99 rs and it does the same thing...when i let off the throttle..it surges like i didnt even close the throttle..i dunno what it could be either...please let me know if you figure it out .........thanks
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Old 04-15-2005, 06:30 PM   #8
GlobalWaste
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im no professional but isn't the bucking you're speaking of (rolling in first gear) just from the engine running rich? My 02 wrx does this as well and so did the other 02 wrx I've driven.. regarding the surge though, not a clue...
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Old 04-15-2005, 08:35 PM   #9
Keith
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no i don't think it is from running rich.


more detail, it happens when I'm just applying light throttle.
at idle, it seems like it is hunting, like it is the tps?
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Old 04-15-2005, 10:00 PM   #10
Davenow
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My car was doing the same thing ever since my motor went bad, I was seeing WAY high EGT's and whenever that happened (at LOW boost 90% of the time, like 1-3psi)
it did exactly what you are describing. It was from running LEAN.

I added a bit of fuel to the maps and it seems to have fixed the surging. Do you have an EGT gauge in the car?
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Old 04-15-2005, 10:42 PM   #11
Keith
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naw I need to get one
oh and some money to buy one
headers are tapped, just need the probe and the egt gauge
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Old 04-16-2005, 03:52 PM   #12
dubrXSti
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Good luck fixing it and keep us posted
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Old 04-17-2005, 08:55 PM   #13
Davenow
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do you have any connections at any service shops that may still have the last generation smog check machines? If so, get them to read the car and see how rich/lean it is running.


Also, Keep in mind that my experiences with this may be SO VERY different from your situation, as my motor is basically blown, so there are a lot of variables that could be causing it in mine...
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