misfire po303, tried the usuals.. now what.

[bustedbolt]

hello,

 

96 subaru legacy 2.2 AT brighton wagon 129k timing belt done @110

 

I get a po303 ocasionally to often. first happened going 70 uphill in WVA in december.

 

the history part:

It always seems to be 303 (but I didn't have a code reader on the first trip problems so I can't say for sure. I often disconnected the battery to freshen things up- since then have traveled with the code reader so I can clear it)

It was really bad from there I got some plugs and wires at a autozone;not so much help.

Passed a subaru dealership few miles after that so I bought plugs there and changed them out. things got better. I could travel, but still limped home with stalling whenever I was too hard on the gas. (350 miles)

Then I read here about aftermarket plugs and wire warnings. I did nothing right away since I was just driving around town and the misfire didn't bother me but it happened often in the first block. Maybe I put on 350 miles since december.

So I recently changed the plugs, wires, and the COIL pack- subaru of course. ran some seafoam too.

Haven't had a problem since then -four weeks-50 miles driven. passed inspection too. ran it hot out on the expressway. starts fine, idles fine (just have that mystery subaru in DRIVE vibration)

 

NOW:

Girlfriend borrows car and calls saying po303 stall at deceleration about 2 hours into a highway trip.

 

So I have tried the obvious, and searched the boards reading these threads- seems like people disappear before they solve things.

saw the Endwrench notes - thanks to whoever keeps posting those!

 

where do I go from here? Is my problem the same?

 

thanks,

 

Brian

[nipper]

mystery drive vibration?

 

Have you checked the fuel injector?

 

nipper

[OB99W]

[...]I get a po303 ocasionally to often. first happened going 70 uphill in WVA in december.

 

[...]So I recently changed the plugs, wires, and the COIL pack- subaru of course. ran some seafoam too.

Haven't had a problem since then[...]

 

NOW:

Girlfriend borrows car and calls saying po303 stall at deceleration about 2 hours into a highway trip.

 

[...]

Misfire is typically related to ignition or fuel-delivery (let's assume the cylinder itself is healthy). Since you've replaced plugs, wires and coil, and the code is recurrent for only one cylinder, it's likely that ignition isn't the problem now.

 

Since the misfire apparently is intermittent, it could be due to a poor electrical connection to the #3 injector (either at the injector or ECU end), some other injector/ECU electrical problem, or that the injector has a mechanical fault. You could disconnect the injector and check for corrosion at the terminals. If you have a multimeter, you could verify that there is at least 10 volts at the connector with the ignition switch on. Also, check that injector resistance is about 12 ohms; although they vary somewhat, it typically isn't more than a couple of ohms to either side of that. If you suspect the #3 injector, you might try swapping it with another cylinder's and determine if the problem moves with it.

 

See: http://endwrench.com/images/pdfs/ProperInsideEWFall05.pdf

[eagleb]

This may or may not be of use...

 

I was getting a P0304 code on uphill stretches at ~35-50 mph. Got a bit better with new plugs, wires, and a new #4 injector, but the problem still came back.

 

Earlier in the year, I took it to a Portland shop, and had my head gasket diagnosed as terminal.

 

While they were doing the HG swap, I had them clean the valves. Since the valves have been cleaned, I have not been able to reproduce the P0304.

 

Maybe you have a very dirty or burnt valve?

 

p.s. I'm no mechanic, just relaying some information in what seems like a similar situation.

[bustedbolt]

thanks all,

 

I will take a look at the injectors this weekend and get back.

 

 

brian