Misfire, Sluggish, Bad gas mileage - ONLY WHEN WARM

[STAROHMER]

Hey guys, I have a 2002 Legacy GTB and have been having the most frustrating issue.

It started a couple months back, and it only happens when the car is warm, it seems the longer it is running the worse the issue gets. It first started with a small periods of misfiring, then it would snap out of it and run great, the weeks went by and the periods of misfiring would be more frequent and last longer. A few more weeks went by and then it started to feel like more cylinders were starting to misfire, and it was almost constant when the car was warm, I also did smell gas fumes on initial start up. Fast forward until now, once the car is warm, it is almost un-drive able. It feels like it is practically running on one cylinder, zero power. It will sometimes snap out of this mode and drive fine for a few minutes, and then out of now where, Boom the misfires start again.

I have changed the coolant temp sensor and the ignition coils are fairly new (10,000 kms). I am stumped and am wondering any suggestions so I don't pour money into things that won't help.

Thanks, 

Aaron

[doublechaz]

First two questions:  Do you have any test equipment at all?  How old are your oxygen sensors?

 

If your oxygen sensors are 200,000 miles old there is a good chance that is your problem, but it would be best to take measurements and find out for sure what the problem really is and then fix just that.

Your best bet for test gear would be anything that can plug in to your OBDII port and read live engine data.  From there we can see if your data makes any sense, if it shows something out of normal range, any codes, etc.

[STAROHMER]

1 hour ago, doublechaz said:

First two questions:  Do you have any test equipment at all?  How old are your oxygen sensors?

 

If your oxygen sensors are 200,000 miles old there is a good chance that is your problem, but it would be best to take measurements and find out for sure what the problem really is and then fix just that.

Your best bet for test gear would be anything that can plug in to your OBDII port and read live engine data.  From there we can see if your data makes any sense, if it shows something out of normal range, any codes, etc.

1. I do have some test equipment yes, I do believe the 02 sensors are original, and the car has about 150,000 kms on it.

2. I was able to plug in a code reader and it gave my the following code: PO118. It was not displaying live data as it is a JDM model and apparently they output different readings compared to the American ones? Is this true?

[doublechaz]

At that mileage it would be up in the air if the O2s are good.  They could be fine, they could be used up, depends on how things happened to them during that time.  I wouldn't feel comfortable saying "just replace them" without some test data.  If you have a multimeter and can get connected to the sensors while it's running you can watch for the correct type of voltage swings to see if they are ok, or if they are stuck or lazy.

I don't know about JDM lacking OBDII live data.  That could be.  Seems like they wouldn't build two kinda of computer flash for JAP and US markets, but there are big differences between the markets, so maybe they would do that.