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Old 07-29-2021, 10:42 PM   #1
tharex
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Default 2006 WRX - How should I troubleshoot an electrical related misfire?

2006 WRX - 180k miles - Snorkle delete, turbo back, DW 255.

I replaced the stock downpipe as it was rusting at the flanges with a High flow Invidia which now completes my full Invidia turbo-back exhaust. I flashed with a local tuner's profile to get me on the road.

As soon as I took it out the CEL flashed, and AP read P0302, P0304. Misfire -_-

That was more than a month ago at this point.

I've replaced the charge tubing with the Mishimoto 3 piece set to rule out any tears with the intake piping. New Cyl4 coil pack and plugs all the way around (AP only reads roughness on Cyl 4). Flashed back to Cobb's Stg 1. It actually made it run worse. Flashed back to the local tuner's profile.

I think this is an electrical issue because I pulled the plug on the passenger side to relieve fuel pressure while trying to replace the fuel pump assembly gasket. It was the green plug into a white socket (next to an all brown plug) in the passenger footwell. It didn't actually help at all so don't do it.

Anyway, my passenger side headlight harness melted and I noticed a melted earth coming off the intake mani right next to the wastegate. I replaced both but no luck. So I assume there could still be another melted earth or a bad connection somewhere causing electrical issues resulting in a misfire.

How would I go about finding it? I have a multimeter but no idea where to begin.

EDIT:

Compression test complete.

Cyl 4 - 25
Cyl 2 - 130
Cyl 3- 120
Cyl 1 - 130

Anybody want to buy an 06 WRX?
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Last edited by tharex; 08-08-2021 at 01:41 PM.
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Old 07-30-2021, 08:18 AM   #2
undyjr
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I seem to recall a You tube video where they were chasing an electrical issue. It was a GR chassis and they found a fuse block behind the glove box. You can also download a factory service manual on line, they have very descriptive wiring diagrams.
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Old 07-30-2021, 10:24 AM   #3
xtremewlr
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P0302 is a cylinder #2 misfire.
P0304 is a cylinder #4 misfire.

You said you replaced the #4 coil pack. Have you replaced the #2 coil pack as well? Are you still getting the misfire codes at all?

If you're still seeing misfire codes, pull the coil pack for the bad cylinder and move it to another location to see if the misfire code moves with the coil pack. That's a fairly surefire way to see if you have a bad coil.
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Old 07-30-2021, 07:32 PM   #4
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^^^agreed. Good advice

While your in there
Pull plugs
Make sure they look same
If yes, then pretty sure electrical issue(coil pack or coil pack harness/pigtail)
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Old 08-01-2021, 07:03 PM   #5
tharex
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Quote:
Originally Posted by AliBenn View Post
^^^agreed. Good advice

While your in there
Pull plugs
Make sure they look same
If yes, then pretty sure electrical issue(coil pack or coil pack harness/pigtail)
When I pulled all of the plugs 1, 2, and 3 looked burnt to a crisp. 4 was pretty oily.

I did not do the pack on Cyl 2 as I donít get a roughness count the way I do cyl 4 and it sometimes goes away with just a P0FFFF and a cyl 4 misfire being read.

Could a bad cyl 2 pack cause cyl 4 to misfire? Surely not.
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Old 08-01-2021, 07:05 PM   #6
tharex
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Quote:
Originally Posted by xtremewlr View Post
P0302 is a cylinder #2 misfire.
P0304 is a cylinder #4 misfire.

You said you replaced the #4 coil pack. Have you replaced the #2 coil pack as well? Are you still getting the misfire codes at all?

If you're still seeing misfire codes, pull the coil pack for the bad cylinder and move it to another location to see if the misfire code moves with the coil pack. That's a fairly surefire way to see if you have a bad coil.
Misfire on cyl 4 with a roughness being counted. Thatís after replacing the pack and all 4 plugs. Cyl 2 misfire comes and goes. So I didnít replace the pack. I wanted to see if the pack on cyl 4 fixed it first before spending any more money on this issue.
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Old 08-01-2021, 09:28 PM   #7
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Hmmmm
As u said had melted HL harness/pigtail

I would concentrate on really inspecting all 4 coil pack pigtails
Look for cracks/melting

When u say 3 of 4 plugs were burnt to crisp
Were they white or black burnt?
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Old 08-02-2021, 08:06 PM   #8
tharex
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Quote:
Originally Posted by AliBenn View Post
Hmmmm
As u said had melted HL harness/pigtail

I would concentrate on really inspecting all 4 coil pack pigtails
Look for cracks/melting

When u say 3 of 4 plugs were burnt to crisp
Were they white or black burnt?
White burnt.

Probably 20k or 30k miles on them. Perhaps less. I changed them last year sometime and I commute quite a bit.
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Old 08-03-2021, 02:23 PM   #9
xtremewlr
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Quote:
Originally Posted by tharex View Post
Misfire on cyl 4 with a roughness being counted. Thatís after replacing the pack and all 4 plugs. Cyl 2 misfire comes and goes. So I didnít replace the pack. I wanted to see if the pack on cyl 4 fixed it first before spending any more money on this issue.
Ok, so ruling out the plugs with new ones and replacing Cyl #4 coil pack, all good.

Now, Move #2 coil pack to another cylinder and see what happens. Does the misfire follow it? Move # 4 to a different cylinder as well and see if the misfire follows that coil. Don't need to replace them right away, just move them around on the engine.

If the misfire is following the coils, then replace the coils. If the misfire doesn't, then the issue is elsewhere.

Also wouldn't hurt to verify that all your ground straps in the engine bay are still intact and don't have corrosion at either mounting spot.
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Old 08-03-2021, 10:56 PM   #10
AliBenn
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Again good advice^^^^

Hmmmm
#2 white with misfire code
#4 oily with misfire code

Would definitely do what Xtreme suggests first

Again, would inspect the harness pigtail that plugs into the coil packs
All 4
I had brand new OE short block installed with a constant P0303
Found the engine harness pigtail that plugs into the coil pack cracked (and glued/epoxied together)
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Old 08-04-2021, 04:12 PM   #11
tharex
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Quote:
Originally Posted by AliBenn View Post
Again good advice^^^^

Hmmmm
#2 white with misfire code
#4 oily with misfire code

Would definitely do what Xtreme suggests first

Again, would inspect the harness pigtail that plugs into the coil packs
All 4
I had brand new OE short block installed with a constant P0303
Found the engine harness pigtail that plugs into the coil pack cracked (and glued/epoxied together)
Iím recovering from having my wisdom teeth pulled. Iíll definitely go back to the coil packs this weekend.

Thatís hopeful advice. I was very close to just taking the car in.
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Old 08-04-2021, 06:25 PM   #12
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Get well!

Hopefully issue is coil packs
Im thinking with 180k.and a mentioned melted HL harness
Heat after any long period of time degrades plastic
If u find out that the pigtails from engine harness that plug into the coil packs do not click and firmly seat in the coil packs, u found the issue
You will have to deal with next issue
Subaru only sells the complete harness like $300 or something
Lets cross that bridge when u find exact issue or combo of 2
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Old 08-08-2021, 12:01 PM   #13
tharex
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Quote:
Originally Posted by AliBenn View Post
Get well!

Hopefully issue is coil packs
Im thinking with 180k.and a mentioned melted HL harness
Heat after any long period of time degrades plastic
If u find out that the pigtails from engine harness that plug into the coil packs do not click and firmly seat in the coil packs, u found the issue
You will have to deal with next issue
Subaru only sells the complete harness like $300 or something
Lets cross that bridge when u find exact issue or combo of 2
Thanks.

I managed to pop the hood today.

Swapped packs across from driver side to passenger. Still P0302 and P0304 with a steady 0/100 roughness on Cyl4.

I believe cyl4 clicks into place pretty firmly. Itís difficult to take out without really getting the clip off.

I also didnít remove the harness whilst doing the downpipe which was when this problem cropped up.

The O2 sensor was the other thing I figured and swapped it out for an aftermarket universal one. About 2 weeks ago. No difference.

Iím really trying to avoid going to a shop. I suppose the next step is compression. I have a gauge. Iíll report back once itís complete.
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Old 08-08-2021, 01:35 PM   #14
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Okay what is causing your wires to randomly melt ? You should always disconnect the battery before starting any work on your car. Did you have an engine fire or something? Wires don't typically melt for no reason.
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Old 08-08-2021, 01:39 PM   #15
tharex
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Quote:
Originally Posted by murrdogg24 View Post
Okay what is causing your wires to randomly melt ? You should always disconnect the battery before starting any work on your car. Did you have an engine fire or something? Wires don't typically melt for no reason.
The wire didnít melt. The contact clip between the two wires melted. The contact clip on the bulb melted too.

Iíve always disconnected the battery.
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Old 08-08-2021, 01:41 PM   #16
tharex
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Compression test complete.

Cyl 4 - 25
Cyl 2 - 130
Cyl 3- 120
Cyl 1 - 130

Anybody want to buy an 06 WRX?
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Old 08-08-2021, 02:58 PM   #17
benflynn
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You always wanted real pistons anyways.
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Old 08-09-2021, 11:35 AM   #18
aidanmurphy
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Tragic compression results at least you found your issue. Engine rebuild?
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Old 08-09-2021, 07:46 PM   #19
AliBenn
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Well Crap

Next
1-determine if you want to keep car
2-determine if you want built motor or a stock short block


From recent experience
The cheapest route is stock short block
About $2k for SB from Subaru
Plus all the parts you really need yo replace bc it is free labor (clutch/timing belt)
Host of other costs
My stock SB rebuild was $5500
Not including tune
The built motor, do not want to even guess
Will be more 100% ($2-4k guessing)
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Old 08-09-2021, 08:31 PM   #20
MikeG4936
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Block is probably fine. I had this issue with my 06 WRX last year and it was a cracked exhaust valve.
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Old 08-13-2021, 07:36 PM   #21
tharex
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Quote:
Originally Posted by MikeG4936 View Post
Block is probably fine. I had this issue with my 06 WRX last year and it was a cracked exhaust valve.
Im really hoping itís a gasket or valve issue. I will take it to Subaru once I have the money for them to troubleshoot further. Once I know for sure the issue Iíll decide how I want to move forward. I figure anything over $2k will not be worth the price and Iíll post her up to Craigslist.
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Old 08-13-2021, 08:40 PM   #22
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Man, I am sorry
As mikeG4 says, could be heads(valves)

This might be too much
But
This is old school way to do leak down test

#4 is bad from your post
1st need to get #4 at top dead center
(#1 cyl is easy, I am sorry but another member will have to chime in how to get #4 TDC)
Next take out #4 plug
Stick compressed air hose in #4
IMO the more air pressure the easier but could be done with a electric tire inflator. Just as long as the air pressure is as air tight as possible at spark plug hole on #4(get a buddy to hold the hose)
The listen in these areas
-air intake(air box/air filter or just b4 turbo inlet) if you hear hissing of air would be intake valve on #4(head
-exhaust pipe(yeah rear of car) if you hear hissing exhaust valve (head)
-oil filler tube(where u put oil in) if you hear hissing could be both I and E valves or worse, air pressure going past piston rings and sound coming out/thru bottom end of motor and thru oil filler tube
GL
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Old 08-14-2021, 04:02 PM   #23
tharex
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Quote:
Originally Posted by AliBenn View Post
Man, I am sorry
As mikeG4 says, could be heads(valves)

This might be too much
But
This is old school way to do leak down test

#4 is bad from your post
1st need to get #4 at top dead center
(#1 cyl is easy, I am sorry but another member will have to chime in how to get #4 TDC)
Next take out #4 plug
Stick compressed air hose in #4
IMO the more air pressure the easier but could be done with a electric tire inflator. Just as long as the air pressure is as air tight as possible at spark plug hole on #4(get a buddy to hold the hose)
The listen in these areas
-air intake(air box/air filter or just b4 turbo inlet) if you hear hissing of air would be intake valve on #4(head
-exhaust pipe(yeah rear of car) if you hear hissing exhaust valve (head)
-oil filler tube(where u put oil in) if you hear hissing could be both I and E valves or worse, air pressure going past piston rings and sound coming out/thru bottom end of motor and thru oil filler tube
GL
This is dope. Iíll consider it if I can figure out how to get Cyl4 TDC.

Thanks for this.
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Old 08-14-2021, 09:41 PM   #24
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Let us know man
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Old 09-02-2021, 03:46 PM   #25
tharex
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Quote:
Originally Posted by AliBenn View Post
Let us know man
Shop said there are signs of scoring on the cylinder wall. The valves are all jacked up too so they decided*an engine rebuild was really the only route. They're reputable and I trust them.

In any case.

One of the techs wants to buy the vehicle and to pitch a price. I'm wondering how much I should ask.

180k on the body. ~110k on the tranny. No after-market stuff besides the exhaust.
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