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2001 Subaru outback 2.5l miss/power loss upon acceleration
Hi,
I'm working on a Subaru outback that is missing during acceleration. The vehicle bucks and the rpms jump down and back up again. The engine also loses power while missing and feels gutless. It has a p0420 and a p0442 which I think are unrelated to the problem. The customer overfilled the oil and drove it that way for about a week. Now the oil level is correct. Also I cannot get missfire data from my verus edge on this model so was not able to check that. Any help is appreciated.
Thanks,
Elijah
Hi,
Did I do something wrong with my post?
If I did please let me know, I don't seem to be getting any responses. I suspect an ignition type missfire but I'm new to Subaru they just aren't user friendly to troubleshoot.
Thanks,
Elijah
www.rs25.com/forums/f13/t173940-obd-code...20-p0442-help.htmlMr
Google mentions
replacing o2 sensors for those two codes quite a few times. I'm not saying that being a parts changer is the solution without doing diagnostics, just interested in the discussion and my first response is to do some research to add to it.
Getting involved in discussions because I have a lot to learn still.
P0420 and P0442 are unlikely to have a common cause.
Dealing with the P0420 and the misfire is the priority.
P0420 is basically a check on if the cat is working it, the engine computer compares the output of the post-cat sensor with the pre-cat O2 sensors and if it sees either too little activity on the post-cat sensor or it sees the the post-cat sensor following the hi-lo-hi-lo-hi-lo pattern of the pre-cat sensors it flags up a P0420.
The causes of P02420 can be a number of things not just a faullty post-cat sensor or faulty cat it can be an electrical issue or more often the cause is the cat isn't getting the exhaust gas in a correct fuel-air ratio for the cat to start working. Or as it is a Subaru it would not be the first have the guts taken out the cat for a few more HP.
You would have to look at live data from the pre-cat and post cat o2 sensors and also the short term and long term fuel trims.
But a misfire really screws up fuel trims and the operation of the cat.
Added to the considerations is this is a flat 4 engine and if overfilled with oil this could lead to oil fouling of the spark plugs, the O2 sensors and the cat.
A misfire under acceleration is usually a pointer to a ignition secondary issue although if is back firing through the intake it tends to indicate weak fuel-air ratio.
In any event look at the fuel trims and condition of the secondary ignition --- often spark plugs fouled with synthetic oil don't recover even if cleaned or given an Italian tune up.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
Hi,
Thanks for the helpful replies. I wasn't able to find fuel trim data on my verus edge. What category would it be in on Subaru? I was really perplexed to not be able to find it. I will post again if I find those pids. Is there a SD video you would recommend to better explain fuel trim numbers? I haven't done alot with them.
Thanks,
Elijah
Hi,
It seems like Andy was correct about the plugs getting coated by the overfilled oil. Plugs we're replaced and the problem is gone! Thanks for your wonderful help. If you have any recommendations on informative fuel trim videos from SD that would be awesome.
Thanks,
Elijah
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