I've been having problems when driving MY01 Sport Wagon GX on dual carriage ways as my CEL starts flashing. I've read off the codes (P0303, P0304), cylinder 3, cylinder 4 misfire. However, this only happens when I'm driving on a downward gradient and doing just over 70 mph. (Usually when I back off the accelerator slightly) This can sometimes not happen for months then all of a sudden it will do it for a whole journey!? The engine sounds fine and I can't detect any change whilst actually driving?

I recently changed the spark plugs but this hasn't solved the problem.

I've read a couple of threads regarding a neutral position switch, do you think that this could be the cause of this problem??

Thanks

 

Don't want to state the obvious but did you check the spark plug gap of the new plugs before fitting them? If the plugs in 3 and 4 or not correct that could be your problem. I had dodgy plugs in mine, the car worked fine normally but give it any sort of beans and it coughed and spluttered.

 

Hello Cornish.
It’s very likely that your guess at the neutral switch is correct. I have replaced the switch on my 01 WRX twice in the last 3 years. Mine used to come on at a similar speed while just cruising. Is there anyone near you with data logging software? , not sure what you read the error codes with, but Subaru specific data logging software often includes the facility to monitor the status of your neutral switch while driving, so you will know for sure if it’s that or not.

Keith.

 

Thanks for the info.

I'll check the plugs gaps but I'm pretty sure the problem was occuring before I had the plugs changed.

I read off the codes with a generic OBD reader so I'll try and see if I can get my hands on some logging software and monitor the neutral position switch.

If not I guess I'll have to take it to the local subaru dealer