I just bought an 02 wrx, and have a problem with cylinder misfire's, What should i do

[Kurbstomp]

Hey guys im new to everything subaru, I just bought a pretty nice bugeye its an amazing car but im already having trouble with cylinder misfire's, I dont want to dump money into parts i dont need. What should i look for?

[impretzel]

first, hello and welcome to the site!

you mentioned misfire"s", are more than 1 cylinders misfiring? have you pulled a code? how much do you know about the vehicles service history or previous owner(s)? did it used to belong to an old fart who garage kept it, only drove it on weekends and was up to date on all of its service intervals or were they young, broke and stupid who tried racing everything but didnt know how to turn a wrench?

when diagnosing a car for a misfire it's important to know if its a single cylinder misfire, or if its multiple cylinders. constantly misfiring or intermittently. will it misfire at idle? under load? or WOT?

in order for a combustion in the cylinder to happen, you need Fuel, Ignition, Compression, and Air.

check for fuel pressure. if it was a lean misfire, it could be a fuel filter in need or replacing, or injectors need or cleaning or replacing.

check for spark. spark plugs could be needing a replacement or just could not be gapped properly. i've never seen an 02, but if its distributor type check for worn points inside the distributor. or some plug wiring that could be worn and grounding somewhere instead of leading to the spark plug. also be a good idea to check timing.

check for compression. you could have a leaking valve causing you to lose compression. or it could just simple need a valve adjustment. you could also have a burned exhaust valve causing pre-ignition.

check for air? lol quite simple. make sure your airfilter isnt clogged beyong belief causing a rich misfire.

thats just about all i can come up with. i'm sure others can or will elaborate more on my suggestions. happy hunting!

edit: well damn this thread just put my post to shame lol

IF YOU HAVE A MISFIRE CODE ,PLEASE READ THIS!!!

oh well i tried

[Rico2611]

Check coil pack connection had same problem on my 2006 wrx missfire from 1-2-3-4 one of the coil pack connections clip was broke. So i replaced it hooked it back up and ran like a champ. Ta DA

[Kurbstomp]

first, hello and welcome to the site!

you mentioned misfire"s", are more than 1 cylinders misfiring? have you pulled a code? how much do you know about the vehicles service history or previous owner(s)? did it used to belong to an old fart who garage kept it, only drove it on weekends and was up to date on all of its service intervals or were they young, broke and stupid who tried racing everything but didnt know how to turn a wrench?

when diagnosing a car for a misfire it's important to know if its a single cylinder misfire, or if its multiple cylinders. constantly misfiring or intermittently. will it misfire at idle? under load? or WOT?

in order for a combustion in the cylinder to happen, you need Fuel, Ignition, Compression, and Air.

check for fuel pressure. if it was a lean misfire, it could be a fuel filter in need or replacing, or injectors need or cleaning or replacing.

check for spark. spark plugs could be needing a replacement or just could not be gapped properly. i've never seen an 02, but if its distributor type check for worn points inside the distributor. or some plug wiring that could be worn and grounding somewhere instead of leading to the spark plug. also be a good idea to check timing.

check for compression. you could have a leaking valve causing you to lose compression. or it could just simple need a valve adjustment. you could also have a burned exhaust valve causing pre-ignition.

check for air? lol quite simple. make sure your airfilter isnt clogged beyong belief causing a rich misfire.

thats just about all i can come up with. i'm sure others can or will elaborate more on my suggestions. happy hunting!

edit: well damn this thread just put my post to shame lol

IF YOU HAVE A MISFIRE CODE ,PLEASE READ THIS!!!

oh well i tried

Well this seems very helpful however i hate that there are so many causes for misfire. My car threw 2 codes for cylinder 1 and 3, i erased them drove 2 days then it threw the same ones. I noticed the misfire a few times. only at low rpms though, and sometimes idle. I'm afraid to drive it to much like this it is my daily driver. I dont know enough about the previous owner but he was not old and wanted more power out of the car however had PDX Tuning do all the work for it. I could take her there but i cant afford it.

[DiRty Impreza]

I had same problem with my 02 last year. First pull the code, or codes. Find what cylinder, or cylinder's you have issue's with. Check connector's on coil packs like Rico2611 said, they tend to break. Make sure white connector up front and black in rear, cause it does matter. Then I would start by changing plugs. If that doesn't work, swap coil packs. The misfire will follow the coil- pack if its the coil. If misfire changes to cylinder you swapped coil, then there is your problem. However if that is not the case, next i would check injectors. Use Stethoscope, think thats what the tool is called, try to see if u hear a slight noise diff. in injector compared to rest. Lot cheaper then replacing injector like i did. If injector's sound ok, then i would try a compression test and a cylinder leak down test. Hopefully you don't make it that far, and its something simple. Unfortunently i had to replace 2 piston's due to ringland failure. Your compression should be 165 across the board. Cylinder 2 and 4 tend to run lean

Oh then remove that up-pipe on your headers, the cat will get clogged up and destroy your turbo. Like it did mine