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Old 02-22-2008, 04:20 PM   #1
kleen
Scooby Newbie
 
Member#: 69959
Join Date: Sep 2004
Chapter/Region: MWSOC
Location: Madison, WI
Vehicle:
02 WRB Impreza WRX
03 Dodge SRT-4

Default Shuddering on acceleration

Hi,

I recently put my engine back together after doing a bunch of upgrades. Now, it seems when accelerating past 4k the car will start to shudder and push back. I recently did a bunch of upgrades including the XPT 2.5 map although I donít believe this is a tuning problem since the logs look fine. I think this is something mechanical which is also what XPT told me.

The first time I tried to log the car threw 4 CEL's:
P0102 Mass air flow sensor circuit low
P0328 Knock Sensor 1 circuit Malfunction (high input)
P0303 Cylinder 3 Misfire detected
P0113 Intake Air Temp Sensor Circuit malfunction (high input)

Here is a list of my mods:
3" A'Pexi GT Spec Cat-back
BPM Turbo Inlet Pipe
GM BCS
3" Helix Down Pipe
Ported & Coated Intake/Exhaust Manifolds
STi "pink" Injectors
STi Up pipe
VF39 Turbo
XPT Stage 2.5 Map

Last weekend I visually checked for vac leaks and double checked clamps. I also cleaned my plugs and maf. I noticed that my plugs had a lot of carbon build up on them for only having 200 miles. I then took the car for a test run and it only shuddered once and ran beautifully after that.

Then about 3 days later, the symptoms came back. This time only one code which was detected cyl 4 misfire. I have yet to take the plugs back out, but im sure they are full of carbon again.

Does anyone know what would be causing these symptoms or the plugs to keep getting fouled? The car is running at a conservative mid to low 11's at full throttle. It was also suggested that fuel pump might be a problem. The last log I have does show it being at 100% between 3500 - 5k rpm.

I plan on trying to make a vac tester this weekend, but Iím not so sure the problem is vacuum related. I'll post up my last log tonight.

Thanks for your help,
Colleen


Here are the links to the logs. In both logs, the shuddering started around 4500rpm on up

http://spreadsheets.google.com/pub?k...XExvThi4QtSZbg
http://spreadsheets.google.com/pub?k...XEzvnjSbQrw7Qg
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Last edited by kleen; 02-23-2008 at 09:06 PM.
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Old 02-23-2008, 03:00 AM   #2
zachary.berrier
Scooby Specialist
 
Member#: 82476
Join Date: Mar 2005
Chapter/Region: AKIC
Location: Anchorage, ak
Vehicle:
GOD CREATED TURBO
LAG TO GIVE V8'S A CHANCE

Default

it sounds like your running rich enough to choke it out, whats the afr's looking like, nevermind just saw. well if the plugs are all carboned up and fouling out, this is generally do to running to rich. is that afr from a true wideband or from the ecus front sensor cause thats not a good tuning tool using an access port and reading that.
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Old 02-23-2008, 09:07 PM   #3
kleen
Scooby Newbie
 
Member#: 69959
Join Date: Sep 2004
Chapter/Region: MWSOC
Location: Madison, WI
Vehicle:
02 WRB Impreza WRX
03 Dodge SRT-4

Default

I added the logs to the original post.

Yah I am just going by the front sensor unfortunately. Im working on finding a deal or trying to borrow a wideband though.
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