Misfire cyl. #1

[Garrison]

I'm trying to track down the solution to a misfire I've been experiencing for quite some time now. I've replaced the sparks, wires, and coilpack. I've also cleaned my injectors, so it is unlikely that fueling is the problem either.

Does anyone have any possible solutions to fix this obnoxious misfire?
It's only cyl #1 and the CEL for it only pops up on very long 400+ mile road trips.

Thanks

[d1giPhux]

Do you have any exhaust leaks? Check between the CAT pipes and also in between the first cat pipe and headers. That was causing random misfires on all my cylinders. However yours seems a bit more specific. I'd still check it however. Also reset your ECU.

[Garrison]

I'll recheck the exhaust, it's possible that I mis-torqued a bolt or two last time I was in there.
Also, I've reset my ECU a couple of times. I feel the misfire anytime I'm at idle so it's gotta be something prevalent.

[d1giPhux]

Hmm, yeah, I never felt my misfire. So your actually feeling it bog down or whatever? Any other symptoms you can describe?

[02_Legacy]

Do you have UEL headers?
Right after I put on my UELs I got that code once, I didn't think anything of it because I ran it for a little while with no headers :twisted:
However it has recently come to my attention that I have very negative (-10 to -13) fuel trims at idle. I think the UEL's may be playing with the o2 sensor some how. If it did lean out the mixture enough it could cause a misfire.

[Garrison]

Hmm, yeah, I never felt my misfire. So your actually feeling it bog down or whatever? Any other symptoms you can describe?
Nope, it runs fine once I apply throttle it seems to disappear, though I'm sure I'm losing out on power :(

[Huffer]

Crank sensor?

[Garrison]

Crank sensor?
I'm afraid I'm pretty well in the dark about that and have no clue where it is. However, I saw a video on youtube about cleaning the cam sensor, so I'm off to do that now.

[Garrison]

I cleaned the cam sensor very well, and whilst fiddling around in the engine bay, I looked behind the crank pulley to see a (very dirty) sensor back there, I assume that's the one you were talking about huff? I pulled and cleaned the hell out of that one too. I'm gonna start it here soon see what's what in terms of updates.

[Garrison]

Okay, I pulled the "-" terminal, and reset the ECU by holding down the brake for a while.

The cleaning certainly helped the car, but the misfire is still there. Not as obvious, but still there. You're suggesting replacing the crank/cam sensors?

[Huffer]

That's a possibility - but just cleaning the sensors helped - so to me that suggests somewhere the car isn't getting appropriate signals. How is the grounding system? Much corrosion around the battery?

[Garrison]

No noticeable corrosion on the battery terminals, but I have not done the "grounding mod" yet. Does that help?

[nikolaus.conrad]

I'm just throwing this out there, but check your ignitor. It's the little black box on the firewall, about the size of a box of matches. If you have corrosion under that, you won't have a good spark. It takes about 5 min to check and clean, I feel it's worth a shot =]

[d1giPhux]

Yeah definitely clean any grounding wires out.. that can cause lots of weird issues.

I wonder if you scanned the issue again if it would come out with the same misfire code. At first mine seemed like it was just cyl 3 &4, but then went to 1&2 as well and randomly.

Do you have your old wires by any chance?

What if you try unplugging your CYL 1 wire and running the car? Then plug it back in and test again.

Do you use di-electric grease on your spark plug wires? Is your coil grounded out properly. I know this sounds weird, but make sure that the surfaces on your coil are clean, where they touch against the metal on the manifold, as well as where the bolt that goes through them touches the metal.

[Garrison]

I'm just throwing this out there, but check your ignitor. It's the little black box on the firewall, about the size of a box of matches. If you have corrosion under that, you won't have a good spark. It takes about 5 min to check and clean, I feel it's worth a shot =]
I'll definitely give it a shot tomorrow!


Yeah definitely clean any grounding wires out.. that can cause lots of weird issues.

I wonder if you scanned the issue again if it would come out with the same misfire code. At first mine seemed like it was just cyl 3 &4, but then went to 1&2 as well and randomly.

Do you have your old wires by any chance?

What if you try unplugging your CYL 1 wire and running the car? Then plug it back in and test again.

Do you use di-electric grease on your spark plug wires? Is your coil grounded out properly. I know this sounds weird, but make sure that the surfaces on your coil are clean, where they touch against the metal on the manifold, as well
as where the bolt that goes through them touches the metal.

I don't have my old wires, and pulling the wire to cyl 1 causes the car to run like shit.
Also, the code is so random that scanning never pulls up anything unless the CEL is illuminated. While I'm cleaning the ignitor I'll check for any grounding issues. Anywhere specifically I should check?

[Garrison]

A few updates for today:

I pulled the ignitor and cleaned it; no rust or corrosion to speak of, but it certainly was a bit dirty back there. Once I finished that I decided I wanted to seafoam the system after I found all that junk from the catchcan to the pcv. So I did, and low and behold the miss is gone now at idle.

That being said, upon restarting the car, the CEL did illuminate for misfires on cylinder 1 & 2 (wtf :roll: ), but I assume that was due to the car dying once whilst seafoaming and not giving it enough throttle. Silly me.
But as of now, my idle is smooth as butter, even after higher RPM lift, which has never been the case before.

[nikolaus.conrad]

Awesome!

[chuckthefuk]

A friend had a EJ251 and bad crank sensor wiring caused no starts most of the time but at the odd time it would cause #1/#3 to misfire.. Replaced and all was gravy..

When you changed the plugs did cyl #1 plug have oil on it?

Whats the current condition of your oxygen sensors? Heavily used.? Multiple re-and-re? Frayed wires? Replaced @ ???

I am assuming your timing is bang on since you only have this come up after long drives but by any chance can you confirm its on time?

[Garrison]

A friend had a EJ251 and bad crank sensor wiring caused no starts most of the time but at the odd time it would cause #1/#3 to misfire.. Replaced and all was gravy..

When you changed the plugs did cyl #1 plug have oil on it?

Whats the current condition of your oxygen sensors? Heavily used.? Multiple re-and-re? Frayed wires? Replaced @ ???

I am assuming your timing is bang on since you only have this come up after long drives but by any chance can you confirm its on time?

Cyl #1 did not have oil on the plug when pulled, just carbon.

O2 sensors are old, I haven't replaced them as long as I've used the car, and I did have the turbo/added fuel on it for a while, which blackened the rear* O2 sensor.


I'll check the timing on the crank, but I seem to remember it being spot-on.


The miss has reappeared; though different in characteristics. Now, it has a very distinct stumble every few/10 rotations of the crank; where as before it would stumble and get itself into a funk for a longer duration. So, improved, but not gone.

[nikolaus.conrad]

How old are the spark plugs? Is the gap the right size?

[Garrison]

How old are the spark plugs? Is the gap the right size?
A couple of thousand miles old at most.

Allow me to dispell a myth I seem to see a lot around these forums as well as others; if you buy the spark plugs that are specific to your car, they are gapped properly from the factory. While always good to check, I have yet to find a sparkplug that was even .001" off where it was supposed to be out of the box.

So, in short, yeah the sparks are gapped correctly.

[chuckthefuk]

Agreed but after extended use they do need to gaped again.

[96LegacyWagon]

i noticed that when i switched from the normal plugs to platinum x2 (2 arms instead of 1), it fired differently, then again there were other things involved that could have caused that too

[02_Legacy]

Do you have UEL headers?
Right after I put on my UELs I got that code once, I didn't think anything of it because I ran it for a little while with no headers :twisted:
However it has recently come to my attention that I have very negative (-10 to -13) fuel trims at idle. I think the UEL's may be playing with the o2 sensor some how. If it did lean out the mixture enough it could cause a misfire.

did you ever consider this? you never responded so I don't know if you saw it or not.

[Garrison]

[quote="02_Legacy":37z3odkb]Do you have UEL headers?
Right after I put on my UELs I got that code once, I didn't think anything of it because I ran it for a little while with no headers :twisted:
However it has recently come to my attention that I have very negative (-10 to -13) fuel trims at idle. I think the UEL's may be playing with the o2 sensor some how. If it did lean out the mixture enough it could cause a misfire.

did you ever consider this? you never responded so I don't know if you saw it or not.[/quote:37z3odkb]
Apologies, no I'm using oem headers.

[Huffer]

Could now be fuel delivery, or even a carbon deposit in the cylinders... is it a stumbling idle or actual misfire?

[Garrison]

Could now be fuel delivery, or even a carbon deposit in the cylinders... is it a stumbling idle or actual misfire?
CEL and frequency of event leads me to believe misfire.

[Garrison]

April 14th update:

I got misfire codes for cylinders 1 & 2 yesterday, and once cleared they came back almost immediately, but when cleared again did not return. Then, driving to work this morning, I exited the interstate, the car died at a traffic light, but restarted fine with no further trouble.

Any further ideas?

[02_Legacy]

can you get a scan tool hooked up to read your fuel trims? I read that sometimes as the o2 sensor fails it will read richer which will pull fuel to the point of misfires. Its worth a check.

[Garrison]

can you get a scan tool hooked up to read your fuel trims? I read that sometimes as the o2 sensor fails it will read richer which will pull fuel to the point of misfires. Its worth a check.

I'm starting to think o2 sensors as well. I've got a subaru master tech taking a look at a transmission oil leak later this week; I mentioned the misfire to him and he said he would simply have to take a look at it.

Will update with his diagnosis, hopefully it can help everybody else out who's experiencing this ridiculous problem.

[r3v_v3ng3]

My friend, who owns a tuning shop, stop by today to peep out what I have been up to with my car and he told me he diagnose a couple of subaru (forester and i believe a legacy) who's been having missfires. He told me to not to overlook the little stuff. One of them was the injector orings (which became brittle) and the other was the gasket between the big intake air box on the forester had a small leak that would cause a lean condition. Hope that helps

[Garrison]

Update for you all.

It's been almost a month now, and I'll detail what I've done:

Replaced front O2 sensor with OBX unit
Sprayed 1/3 can of carb cleaner in intake manifold
Cleaned MAF
Cleaned TPS
Cleaned IACV

I've been on 3 longer road trips >100 miles now and the code has not returned. The idle is not completely smooth yet; but the code seems to be gone.

[chuckthefuk]

no seafoam?

[Garrison]

I'll be doing a can of seafoam in two treatments, but it's definitely on the to-do list

[chuckthefuk]

at a boy!

[Garrison]

Thanks :grin:

Funny story today. Going to and from my airforce interview is 250 miles, and only on the last 30 does the CEL pop up. "Oh NOES!" I thought, thinking the misfire code was back. Nope, PO440. I guess seafoam really is in order, haha. All the system checks showed complete though, so once I foam it up, all should be good in the hood. Or, rather under it, I suppose.

[02_Legacy]

umm... seafoam is not going to cure a P0440.
With a P0440 first check your gas cap, if that is not the issue it is most likely going to be the vent solenoid or purge solenoid. It could also be a leak in the EVAP system somewhere.

[Garrison]

Can I disable (unplug) the vent/purge solenoid? I know that they don't work, the gas tank backs up all the time when filling with fuel. So if I had a guess, it would lie there.

[chuckthefuk]

don't mess with your evap system.. unplug the purge valve.. clean it.. reconnect it. Common problem with Subarus..

The last thing you want is a constant code..

[Garrison]

Okeedokie,

Seafoam: twice treated, used 2/3 of can.
Carb-cleaner in the IACV with the top removed for full articulation
Electronics cleaner on the purge valve, injectors, cam sensor, and any other sensor I could find

Car runs with no hint of a miss, smooth idle, and with any luck that PO440 shouldn't return.