Frequent Cylinder 4 misfire code...Need Help

I'm hoping somebody here has a fantastic piece of information because I'm torn on this one. Money is tight and these parts aren't exactly cheap anymore so I'm trying to get it right in as few shots as possible.

 

My 1999 Legacy Outback 2.5L recently started running quite rough and throwing misfire codes my way. I've had it about 18 months and quite like it. I consistently get a flashing Check Engine Light (every time I drive and even multiple times on short trips) that reads as a P0304. I can easily tell right when the light will flash most of the time as the engine runs very rough.

 

A few things throw me off though. I also have had an appearance of codes P0303 and P0302 pop up (only once a piece and the P0302 was before the consistent appearance of P0304). I have also had a couple appearances in the past of an EGR code (can't remember the number anymore) and despite running checks on it and the lack of codes I still suspect it is not working properly. I started noticing the engine running VERY rough upon cold start when the weather got cold (I live in MI) and the codes and poor performance were soon to follow. Also I have been long frustrated by flickering lights at idle speeds which I suspect is a failing voltage regulator in the alternator (?).

 

The resistance checks out fine on the coil pack, however the posts for cylinder 3 and 4 both have mild discoloration and 4 even had some mild corrosion when I purchased the vehicle (I cleaned it up and bit and it doesn't seem to have gotten worse). My mpg have dropped to about 12 and you can smell that something is not right.

 

Within the past 18 months i have replaced the valve cover gaskets, plugs, wires, clutch, and a few other little things. My guts tells me to just go out and buy a new coil pack but I don't want to blow the cash if I'm missing something.

Any guidance is GREATLY appreciated by the way and thanks will be in order

hmm...misfire...i'm not too experienced with subaru's and misfires, but my audi had an issue at 92k with a detremintal misfire to a point where the engine died right on the road; popped the clutch, cruised to the side of the road, and called my friend haha. turns out it was the coilpack (not the best in the business), but damn it was like someone stuck a wrench in the crankcase. take it for what it's worth i guess, but if the resistance checks out, it's tough to say boo to that.

Sounds like you might have clogged injectors possibly. Try running some injector cleaner through them. I use gumout extra concentrated fuel injector cleaner and it works well. Its a cheap thing to give a shot.

Very carefully remove one wire at a time from the coil pack with the engine running. It might help to stand on a rubber mat and wear an electrical safety strap - metal wrist band you clamp to the chassis. The engine should run rougher or stall when you pull the wire from the coil pack. If one does't, then you at least have it narrowed down to a cylinder ( #4 from the misfire code.)

 

FWIW, I was getting misfires along with P0400 (EGR Flow malfunction) a little while ago. The P0400 code would come on once a week at first, and then, 6 months later, was on constantly. I misfired more often, but only rarely, and only when cold. Unfortunately, I replaced the plugs, wires and fixed my EGR problem - happened to be a stuck vacuum solenoid - so it's tough to figure out whether it was the EGR causing the misfire or the plugs/wires. Since you've already replaced the plugs/wires I would stick with trying to get your EGR system operating properly. Look up my name on here and nasioc for what I did to trouble shoot the issue.

 

How often does your P0400 code come in? Is it just sporadically and clears by itself? If so, that's how mine started.

I have only had the EGR code once. It was last winter and after toying with the EGR system (didn't do anything in particular) the light stayed off and nothing dramatic happened. I check the valve's operation once in a while and it seems to occasionally not work, but based on the frequency of the misfire code I can only assume that it's unrelated.

If those times when it doesn't work are just after starting the car, it's normal. With the car fully warmed, blipping the throttle will always produce a response. Just keep it in the back of your mind, since you really don't want to replace parts you don't have to.

We might be in the same boat digital except been on it for 20k buahaha. One day my engine started to do all your symtoms, run ruff, throw misfire code in cylinder 4 and all that bad stuff. Changed out everything from coil pack to new wires, to spark plugs, everything was fine. no oil in where the spark plugs were i feared for the worst and had it tested. I had low compression in the 4th cylinder it suppose to be 150 or somthing i had 32lbs of preasure. The subaru dealership and another mechanic rulled it out as a burnt valve thats causing it. You think this is somthing that you fix right away or stop driving the car till its fixed. But me NOPE! haha i use the car for work and have a 80 mile commute each day so i had to drive it and couldnt drive my outback as during that time my mom has wrecked her car and needed to use mine to go to work. So for a good 6 months now i been using my car, mom has her car back, yet my lgt still drives buahaha. I have the engine with me and a friend to help me put it in, but im corious as to how long I can go. Have taken 3 200+mph trips in the car and put over 20k since the problem started. To this day itI do regular oil changes and it runs like a champ!

 

But enough about my rant, check your spark plugs you might have a bad one or bad wire, i bought a coil pack and since it wasnt I was able to return it, just dont get it dirty. Spark plugs are cheap so replacing those is easy, and if all fails you get a compression test.

 

Thats just my 0.02

200+ mph trips!!!? Holy moly! : P

200+ mph trips!!!? Holy moly! : P

 

 

haha yup i live in the bay area and took 2 trips up to reno to play in the snow, and a trip down to la, hahaha i think i might do my engine swap right when dail hits 200,000 haha, almost there got another 11k to go haha

i think he was talking about the number 200 MPH hour...idk im confused? you were going 200 mph in your legy. wonder how that felt

i think he was talking about the number 200 MPH hour...idk im confused? you were going 200 mph in your legy. wonder how that felt

 

 

a trip to la, and two trips to the snow and back, planning another la trip during spring break!

 

but not to hijack the thread, try out some of the things i mentioned digitial and let us know what happening

how rough. cuase i have a problem i think but it was so small only i can feel the diff

Ughhh. 4th set of plugs in 60k miles because of cylinder number 4 misfire. Might run some seafoom through there.

wow. this thread is so old, I see amp!

wow. this thread is so old, I see amp!

 

Oh boy he must of got a life time ban lol

you need to have a compression test done. you may have a burnt exhaust valve in #4 cylinder. i hope not but a compression test should tell you something.

 

and or have the valve clearances check. the valves are supposed to be adjusted every 105k miles. lots of folks don't do it. or buy cars that have not had it done.

 

how many miles on the car?

hey man i just had the same problem with my 99 legacy outback 2.5 i took it to subaru and they pulled the codes po301 and po303 i had two cylinders down but what happened was the coil got to short and then wore my plugs down and shorted out my wires so i would start with changing the coil wires and plugs

^this