misfire

I keep getting cylinder 1,2,3&4 misfire code's should i change the coil packs, my car is running fine no loss of power, Ive already changed the spark plugs . anything helps thanks

 

Post-MAF leak?

 

How do you know it's running fine with no loss in power? Have you done a compression test?

 

I bought the car the beginning of December and it ran fine no CEL. then i got the recall for the fuel lines it was at the shop for like two weeks. got it back still ran fine same as how i got it. but a couple weeks after i got it back the first misfire code showed up. changed the spark plugs and it didn't show up for a while. Now it randomly shows up while driving. where would i get the compression test and how much would it cost.
thanks

 

do it urself its free to rent the tool other then the security deposit at most tool places.

 

or buy one for under $20... its very easy to do too... also why in the crap was it at a shop for 2 weeks fixing the fuel smell recall!!!??? haha

 

I have no idea they kept telling me the parts were late idk tho right before i left the car the mechanic said he had never done one of these before very reassuring. they gave me a free rental car tho ( 08 Mazda 6)

 

what brand gas you run??

use BP or Shell

 

yeah man if your gas is not high enough octane then it will cause missfires, anything under 92 i start to feel it, i only use 93 at the bp by my house or the one by my work.

 

highest around here that i can find is 91

 

theres your problem, buy some octane booster and try to put some of that in and see if it helps

 

There may be a few things in the thread I worked on when I was having a cyl 2 misfire. http://mnsubaru.com/forums/showthread.php?t=35831 This should answer a few questions and give a couple more things to check out.

 

If the car is new to you, you may not be aware enough to know it is low on power or not. If it is throwing misfire codes, usually it's running pretty bad by that point. A few things that cause misfires:
I've had these:
- low compression (down on power, rougher idle, usually some extra oil blow-by)
- bad injector (rougher idle, gas smell, mis/back fires if really bad)
- coil pack (rougher idle, down on power)

Others people have mentioned:
- bad gas (generally poorer running, temporary), 91 octane doesn't cause misfires, and your ECU will tolerate a bit of pulled timing before it throws a code.
- crank position sensor
- old spark plugs
- bad A/F ratio sensor (front o2) (runs worse, may run too lean or too rich)

When you did the spark plugs (did you do them yourself?) what did they look like? They can tell you if it is running rich or lean, or if a cylinder isn't running as well as others (plug wet, looks different).

The fact that it went away for a while after doing plugs, and then came back might suggest what is happening may be affecting the plugs or spark quality. If you weren't the one that changed the plugs, I'd suggest looking at them as see what they look like. You can buy a compression tester at a parts store for like $20, or pay a shop to do it, should take about a hour of work or so. I'm not sure about the 03 WRX, but my 04 FXT required a bit of work, including jacking the engine up to get the coil packs off to get the plugs out. If you just have a single coil pack, it's a lot easier to work with.

Misfire codes are tough, as they can be caused by a lot of things, and the cost to fix can vary from replacing a bad part to rebuilding a motor, I've done both

 

its not hard on a wrx, just remove the air filter housing on one side and the washer reservoir on the other side then the coil packs come out... not too hard.