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Old 12-03-2011, 12:36 AM   #1
Scooby Specialist
Member#: 199635
Join Date: Jan 2009
Chapter/Region: RMIC
Location: Provo, UT
02-4 rSTI

Default need a favor

hey guys i've been having a hell of a hard time getting my car tuned, there is something mechanical wrong with it and it's being a pain to track down. i need to borrow an sti rear o2 sensor(04-07, unless the 08+still use the same part) and i need to borrow a maf sensor.

doing the maf scaling the car is acting like either an o2 sensor is bad, the fpr is hooked up backwards, or there is a boost leak or something else, at idle the maf scaling points go all over the place from +25 to minus 25% and it's not a tuning issue. it could be another set of bad injectors but this would be the second bad set, things i've done so far:

had solid auto do a boost leak check, they checked it to 22psi and said it was good, brody did the test.

changed front o2 sensor
changed fuel filter
changed spark plugs with ngk iridiums gapped to .27?, one step colder
cleaned maf
checked fuel pressure.
checked fpr routing visually the best i could, i'm 99.9% certain it is hooked up correctly.
changed out coilpacks on the cylinders that were misfiring the worst.

also the car will fluctuate rpm's slightly up and down, and right now won't idle unless i keep my foot on the gas.

i'm about to pull the plug on going topfeed conversion but want to eliminate the rear o2 and the maf sensor from the problems but i've already shelled out a lot on new sensors and etc that weren't the problem. if anyone knows a way to OBJECTIVELY test the maf and o2 sensor then that would be great, but i don't know any way other than maybe read their outputs in romraider but don't know what the acceptable ranges would be. (have it setup on the laptop)

anyone have a maf or rear o2 sensor i could borrow for a day?
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wrxkyle is offline   Reply With Quote
Old 12-03-2011, 01:46 AM   #2
n00b Moderator
Member#: 99397
Join Date: Oct 2005
Chapter/Region: RMIC
Location: Clinton, UT
15 WRX, 83 DR30,
93 R32 GTS-T, 93 R32 GTR


You can come try my parts, but I live in clearfield which is a pretty far drive for you. There is really only one way to hook up the FPR, if it was hooked up backwards the car wouldn't run, unless you are talking about the vacuum line, which should just go to a vacuum source on the IM.
bhhamblin is offline   Reply With Quote
Old 12-03-2011, 01:49 AM   #3
Scooby Specialist
Member#: 183634
Join Date: Jul 2008
Chapter/Region: RMIC
Location: At the "B"
02 wrx/ 92 ss
Booze fueled :)


sounds like some bad valves/compression issue. get a compression and leakdown test before you go any further, to make sure your not running on say 3 valves a cylinder.

Rear-o2 does effect trims, it's not necessary for the system but exposing it to free air while tuning isn't good.
907Bum is offline   Reply With Quote
Old 12-03-2011, 02:55 AM   #4
Scooby Specialist
Member#: 199635
Join Date: Jan 2009
Chapter/Region: RMIC
Location: Provo, UT
02-4 rSTI


ugh, i hope not an engine issue, really really hope not. this all started right after i did the fuel pump, 70mm intake and 1200cc injectors so i have hope that it's something in that mix, most likely the injectors which is why i'm thinking of scrapping them for top feeds that are more reliable and smoother running.

then again a bad motor would be a reason for a built one, but then i'll need a bigger turbo, and go rotated, and the "if you give a mouse a cookie" **** piles up really quick.

i need to go get my brakes re-bled by jason at inovative and have the fpr checked, i'll probably have him do a compression and leakdown. the misfire counts in rr follow the injectors when i switch them around, and cyl# 3 is the one with no misses, while #2 is very bad, #4 is bad, and #1 is meh. (used to be 4 really bad and 2 bad and i switched them back and forth.

if it were a valve or compression issue could that have been masked when the little stock injectors were in there and then greatly exaggerated by the 1200's?

Last edited by wrxkyle; 12-03-2011 at 03:32 AM.
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