I did find when it first came in that when wet or cold it would miss and run rough. found #2coil contact and plug to be carbon tracking and 02 sensor stuck rich. replaced plugs, coils, wires and o2 sensors. that stopped the roughness and noticeable miss fire. but it still sets miss code for 3&4 under load above 5000rpm. checked all the engine compartment electrical conectors only found the air flow meter conector was corroded. replaced the conector and the meter. no improvement. checked compression and cylinder leakage both pass. sent it to Subaru and they checked the calibration and swapped ecu with a knowen good ecu no change. Subaru thought it was either the valve issue or short block problem. replaced with a complete used engine less wiring. still has the exact same issue setting p0303and p0304.
SOURCE: Cylinder 1 misfire on my subaru!!
What you should check first is the spark plug for the #1 cylinder and see if there is a white film on it this would be a sign of a coolant leak which would cause a problem with the O2 sensor
SOURCE: 91 LEGACY STARTED RUNNING ROUGH
The cylinders are numbered as on the spark pack you changed. You might have done better putting the seafoam in the tank as an injector cleaner. Not sure why you changed so many parts, you seem to know how to get the codes from test connector lead hookup and the blink pattern. You might also want to check the fuel rail pressure and the crank and cam angle sensors. Before replacing the injector, swap the #4 injector with the adjacent one and see it the code moves with the injector or stays put. If the code stays on #4, then check the injector wiring, if it moves clean or replace the injector.
SOURCE: Subaru Forester P0303, Cylinder 3 misfire problem
Having the same problem with my 2000 Legacy Outback. A mechanic friend of me said there is a limited number of things this could be (in order of likelyhood): plugs, plugwires, coil, fuel injector, bad compression/valve. He said he has 2 Subarus in his shop with a rough idle and bad gas mileage and both needed new coil packs. The coil packs in Subarus has 2 coils, one for the 1 and 3 and one for the 2 and 4. Each one of those coils has two coil wraps in each. These are wear parts and eventually they wear out. He said in Subaru they usually last 90,000-150,000 miles. So all things considered, he said it is 99 times out of 100 the coil pack. I would shop it around they seem to vary in price wildly from store to store. I found one for my car for $126 while another store had it for $200.
Is the wiring good going to the O2 sensors? Maybe just look the car over and see if you have any bad grounds. They can do weird things. Could be a bad ICU.
SOURCE: 90 Subaru Loyale Engine Miss
The simple solution will cost u about $20. Change out the Coolant temp sensor. Some people call them the master sensor,because they control so many things. Like the operation of your engine cooling fan, your on board computer takes readings off of this thing,and it not only controls your fan,but your FUEL. This little thing can cause all kinds of issues. Like over heating, running to rich or to lean. It can act like you have waterin your gas tank, or rotten varnish gas.it can drive you nuts. When you start hour motormin the morning this little sensor senses the temp ( of coarse) and tells the ECM the temp,in turn the ECM provides a richer fuel mixture when your car us cold.(modern choke if you will. The ECM also regulates how long the injector pulses are as well. As your engine warms up, this sensor tells the ECM, if it's working correctly,that the coolant is getting warmer as leans out your fuel mixture. This sensor can cause all kinds of havoc. Like it will start sometimes ok and at other times it won't or if it does it will be real heavy and want to die. Sometimes feathering the pedal will keep it alive but it will be stumbling to stay on and often die. Other times it will drive fine,then it will start bucking at all speeds,like it's loading up, or running to rich. This sensor can cause your engines fan not to come o. And cause overheating.it can also cause the fan to run when it shouldn't be. I had all of these problems,and rally thought that I hD some old gas a d it had started to varnish up everything, as my Subaru had sat for a couple of weeks while I changed out all of the wheel bearings.but after some detective work and a lot of reading I came to the conclusion that the culprit must be this sensor.I changed it out and now it runs great, and when I park it in the driveway and it reaches temp the driverside fan kicks on now. Can't remember the last time I heard it come on. Lol. The passenger side fan should come on when your AC is turned on, just so you know. And make sure when you put your filter cover and intake hose back on to get them on correctly, or you will get a resonating hum from hour air cleaner. The part is cheap, getting things out if the way to get to the sensor a little tuff, but it will I'm sure solve your problem. Good luck.
720 views
Usually answered in minutes!
×