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Old 01-26-2005, 03:21 PM   #1
Scooby Newbie
Member#: 79032
Join Date: Jan 2005
Location: Baltimore, MD
2002 Impreza WRX

Exclamation 02 WRX doesn't run after sparkplug change

i have a 2002 WRX with the TXS stage 4 (stock TMIC). i was getting the
occasional CEL flashing (knock) when driving on the highway in 5th gear
(about 3000-3500/rpm). since the UTEC firmware hadn't been updated since
about august 2003, i figured it was time to update to the latest.

the update went fine, and the car seemed to run a little smoother for
a while (no CEL), when it started missing slightly (and got a little worse
as time went on). so, i got some OEM replacement plugs and set out to
replace them.

i started by disconnecting the negative terminal on the battery. then i
started on the passenger side of the car by removing the harness from the
MAF on my cold air intake (AEM), and then removed the CAI tube.

i removed the back coilpack (black) first, gently (as possible) pulled
the pack off, then removed the plug. i then lightly applied dialectric
grease and never-seize to the plug (appropriate ends , threaded the
plug by hand, and tightened the plug with about a 1/4 turn, and replaced
the coilpack and harness.

i then repeated the steps above for the the front (white) coilpack and
plug. after the front coilpack was back on, i put the CAI tube back on
and forgot to plug in the MAF harness (this is the only thing i think i
screwed up on).

i reconnected the batttery, hopped in the driver seat and fired her up
(she was using the stage4 map/parameters found on TXS site). naturally
she didn't run well and it was then i remembered the MAF sensor. after connecting
the MAF sensor, i went back and tried again. she would start, the RPMs would
kick up to the normal warmup/idle speeds, then immediatly die. i tried
this a few times with the same results.

so, after taking the plugs back out, verifying the gaps, cleaning the
dialectric grease and never-seize, i put them back in again. same results,
so i took out the new plugs and put back the plugs that were in there before.
same thing again. so, i flipped my map selector to map 0 for stock mode, and
tried again. she actually started, sounded good for about 3-5 seconds, and
then started missing terribly. the car would run like this, although poorly,
and even let me give it gas (with nothing really even resembling a decent
throttle response). if i let it idle by itself, sometimes it would stop
missing, and start idling like normal, but then quickly start missing terribly

i then decided that i would re-flash my UTEC with the latest updates (it
was already running it, but i was out of ideas). so, i re-flashed my UTEC,
and reloaded the stage 4 maps, and tried again. still not running correctly.

at this point in time, there were no codes being thrown, so i had no idea
what the problem was. i didn't touch anything on the driver side, nothing
else anywhere on the car, etc. in an attempt to see if maybe i broke the
coilpacks, i unplugged the harnesses one at a time. the car actually ran
(at least the same, maybe a little better) on *only* the two driver side
cylinders than it did with all 4.

aha! coilpacks, i thought. so, i replaced both the coilpacks i touched with
brand new genuine subaru coilpacks. no love, still the exact same behavior,
but now it finally threw a code. MAF and misfires on all 4 cylinders.

dang, the MAF! so, i shelled out another $200+ for a brand new genuine
subaru MAF praying that it would work. it didn't.

we've looked for vacuum leaks, grounds, reset the ECU a dozen times,
tested the MAF and coilpack harnesses against what the factory shop
manual says they are supposed to be, etc.

i am really sorry for this long winded post, i am hurting for ideas as
is the mechanic who's shop my car was taken to. any ideas, suggestions,
advice, would be greatly appreciated as i am pretty much at the end of my
wits (and savings) from throwing money into replacement parts that didn't help.

thank you all for your ideas and suggestions
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Old 01-26-2005, 07:09 PM   #2
A. Moderator
Member#: 21095
Join Date: Jul 2002
Chapter/Region: TXIC
Location: Miss you, Charlie Murphy.
'09 Crystal red Tintcoat


MAF code was triggered because you tried to start the car without the MAF connected. As far as the misfire codes, did you do anything to the crank position sensor? Also, I'd check up with Turbo XS and see what happens when you disconnect the battery, and cause the ECU to relearn. <---My guess that's the problem, and you need to flash the map that you have in your UTEC back into the ECU.

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Old 03-30-2005, 04:11 PM   #3
Scooby Specialist
Member#: 15904
Join Date: Mar 2002
Location: WA
05 Impreza
09 Tribeca


Did this get resolved?
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