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Old 04-17-2009, 11:28 PM   #1
Aphex28
Scooby Specialist
 
Member#: 11506
Join Date: Oct 2001
Chapter/Region: NESIC
Location: Manchester, NH
Vehicle:
2015 WRX
World Rally Blue+TE37-TA

Default EJ20g throttle issues

Hey guys.

I've got a sedan ej20g with a 16g. It's a GC8B48D and, according to catherineandken, by the trans code on the vin plate it should be a WRX tuned by STi. Either way, I'm running it with a z4.

The car doesn't really respond well to throttle input greater than maybe 20% yet idles fine. On partial throttle it responds well after a small hiccup and runs through the rev range fine. Yet, if I floor it, it sputters and stutters it's way up the rev range. I haven't been able to take it out and put it under any load, but it does all of this in neutral.
With the MAF unplugged it runs like normal and rev's great.


So far:
  • compression test came out perfect
  • Vaccum is in normal range at idle
  • There's no air leaks
  • no codes
  • tried 4 MAF's all the same symptoms
  • Changed and cleaned the IACV
  • changed the plugs to 1 step colder(NGK BKR7E gapped to .028)
  • did the GD coil conversion, and theres strong spark from all 4
  • changed the front o2, cam angle, coolant temp and crank angle sensors as well.
The replacement front o2 is questionable because whomever had it beforehand seems to have respliced the wires back together.
I've already searched beforehand at scoobynet, and it seems like they come up with similar answers as here.

I'm thinking I will try cleaning the boost solenoid, but I'm not sure if this will do it.

I can't really figure out this issue as I've pretty much tried everything.

Thanks in advance!
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Old 04-17-2009, 11:41 PM   #2
rockcrete
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Member#: 196721
Join Date: Dec 2008
Chapter/Region: VIC
Location: Maple Ridge
Vehicle:
1993 GF8 WRX Wagon
Black

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You either have a vac/boost leak or a bad maf or a bad wire..........

I'm voting for leak. What makes you think you don't have a leak?
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Old 04-18-2009, 03:07 AM   #3
Aphex28
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Member#: 11506
Join Date: Oct 2001
Chapter/Region: NESIC
Location: Manchester, NH
Vehicle:
2015 WRX
World Rally Blue+TE37-TA

Default

I just pressure tested it up to around 5-6psi at the shop, I wouldn't have put it down if I was doubtful about it.
There were previously a few leaks, including a crack in the rubber turbo inlet which led to me buying a Legacy SS one for something around $100 from the dealer. Very similar with one nipple in a different location.
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Old 04-18-2009, 01:19 PM   #4
rockcrete
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1993 GF8 WRX Wagon
Black

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The fact that it runs fine with the maf unplugged really points at a leak - it just runs off the map sensor then and you should hit fuel cut if you rev over 3000 rpm or so...... maybe pull the vac tube off the map sensor or unplug it and see what happens.....
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Old 04-18-2009, 01:25 PM   #5
rockcrete
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Location: Maple Ridge
Vehicle:
1993 GF8 WRX Wagon
Black

Default

If you suspect the O2 change it or unplug it and see what happens as well......
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