Misfire troubleshooting (not just codes)

[mmiller2002]

I was asked to create a new thread instead of clogging up the sticky any further.
IF YOU HAVE A MISFIRE CODE ,PLEASE READ THIS!!!

I will try to go down Donkey's list again, and also try datalogging with my AP. Thanks for any advice.


Background:
I just started chasing a P0302 with the bouncing motor on my '02 with 8x,xxx miles with a stock motor and Cobb AP Stage 1 map.

A year or more ago I got the P0302 and swapped #2 & #4 coil packs. Code went away.

This time, to start, I'll put new plugs in and swap the coil packs around and see what happens.

Does that sound like a good start?

PS, I also had a P0171 a couple weeks ago that seemed to go away with MAF cleaning and some post-MAF intake tube clamp tightening.

Next:
OK, new plugs, swapped coil packs around, but now I have 2 misfire codes. And, they didn;t follow the original #2 pack...Ugh.

ugh, originally a P0302, now P0303 and P0301
New plugs, new fuel filter, swapped coils as follows:
#2 to #1
#4 to #2
#1 to #4
#3 stayed put

And, it's not just a code since the engine runs bad like a misfire. How are the misfire codes detected by the ECU? Just a sensor for vibration, or is it some electrical test of each cylinder? In other words, how does it determine which cylinder to flag?

Is there a way to probe the connectors? I hate to throw $$ at parts.
Would a dealer/shop have any special tools that would make it worth the expense? or, would they just throw parts at it too?

Thanks y'all for the time and advice.

Next:
Thanks for the comments and info.

I swapped coils from driver's side to passenger and still got the same P0301 and P0303 codes with rough running.

I'll try an easy reset and drive it a bit and see if it's consistently the same codes and running. I may also recheck my plug gaps.

Is there a safe way to check the harness at the coil pack connector?

Thanks
--------------------------------------------------------------------------------
Yesterday 08:18 AM #50 Donkey
Moderator

You can easily check the connectors with a multimeter or test light but you are on the wrong trail. I highly doubt the issue is power to the coils since the car is actually running. Even missing 1 cylinder would be extremely obvious.
Last edited by Donkey; Yesterday at 08:29 AM.

[mmiller2002]

Recommended from another forum:

"quick test. With the engine running, open your oil filler cap. Is there smoke coming out or can you smell fuel? If so, you blew up a piston. This happened with my last car and you can check this way.

If you do smell fuel/see smoke, do a compression test immediately just to verify."


Just did this test. No gas smell to my nose. No smoke. Does the engine have to be hot?
Still P0301 and P0303 and rough running.
The exhaust smells gassy.

I also sprayed starting fluid around the intake tract and other hoses with no noticeable increase in rpm.

I guess its back to one more swap of the coils and a look at the newly installed plugs... :-(

[mmiller2002]

Thanks for the inputs, I appreciate it.

BTW, the CEL flashes even though the engine runs totally bad.

I did double check the plug gaps. I swapped plugs across the engine today. Left the coils the same. Same results with codes p0301 and p0303, bad running.

If it were the injectors, wouldn't it be so very unlikely that 2 would stick all of a sudden? I hate to try to run it a lot to get injector cleaner through.

I checked some more for intake leaks by spraying starter fluid around all the hoses i could see. And, I cleaned all the grounds I could find. nothing.

I guess I'll try to swap coils back across the engine one more time since I'm out of things I can do, or feel comfortable doing.

[mmiller2002]

Since I'm giving up and sending it to the dealer for injector, compression, leakdown, and timing tests, I guess I'll probably get the timing belt changed while its there. Other than the water pump, what else to do "while they're at it?"

[Anub1s]

Sorry you didn't get any responses there, but the tests you're having the dealership do are what everything basically boils down to. I would make sure to get the tests done before you commit to having any work done on it though. Sad to say, but you may need a rebuild.

[My04STILA]

I might have a solution for you...Since you have a p301 and a p303 u should also have a p0011 right? try removing your AVCS oil screens.

[My04STILA]

go to this link http://www.scoobymods.com/tsb-02-97-...0301#post20301 and keep reading it all the way thru...It should solve your problems

[T0rque]

any oil smell? what did the old plugs look like? I was fouling spark plugs because the inner part of the valve cover gaskets went bad and soaked the plug with oil.

[mmiller2002]

Thanks for the input. I didn't have the P0011. No oil smell, but I did have gas smell, like a misfire.

The TSB is applicable to '04. Would it also be to my '02?

The dealer's tech is puzzled. He doesn't know why the injectors are "wide open at 6.2"

[MainFrame]

I might have a solution for you...Since you have a p301 and a p303 u should also have a p0011 right? try removing your AVCS oil screens.

02 WRX doesn't have AVCS.. therefore it also does not have the screens.

[mmiller2002]

Well...still no resolution. Tech has eliminated everything easy to access. Talked to Subaru for a "few hours" and consulted other techs. I went ahead and had them R&R the timing belt, water pump, thermostat, and associated idlers and tensioners as part of the diagnosis. Nothing.

All sensors appear to be OK. He said that all indicators point to an intake leak causing the ECU to think its lean, maxing the fuel injectors. Next, he wants to pull the intercooler and look at the turbo to intercooler pipe...UGH

Its so rare that take my cars to the shop, this hurts.

[mmiller2002]

After a long ordeal, I think that the root cause may have been a wiring open/short in the harness that goes to the #2 and #4 coils.

Story:
As I was troubleshooting the original #2 misfire, I probably miswired #1 and #3 coils, causing those misfires. While moving the harness to swap coils and plugs, the intermittent #2 misfire went away. This left the #1 and #3 misfires that never left due to miswiring.

Sent car to dealer because I couldn't solve. Dealer didn;t catch the #1 - #3 miswiring and tried everything in the book.
So, I sent the car an hour away to a specialty shop, awdtuning. Within a day, they located the #1 - #3 miswired coils. Ugh.
Picked up the car, driving home, had a misfire again, #2. took it back and in about 2 hours they determined it must be the harness short/open to #2 and/or #4 because it went away when the hareness was juggled/flexed.

I took the harness to #2 & #4 apart as far as I could and retaped/wrapped the wires. So far, so good.

So, lesson learned.

[EvoEatr]

I was just browsing through here and came across your post. I just want to mention. I have come across (on more than a couple occasions) that the two large harness connectors in front of the washer fluid resevoir can become loose/ the wires can back out a tad and cause exact problems like this. just something to throw into the back of your mind if you ever run across this again.

[mmiller2002]

Thanks for the tip

[mmiller2002]

happened again. #2 misfire code and rough running. disconnected and reconnected the #2 coil connector and all is fine. may have to replace.