misfire mystery

Everyone likes a good mystery to solve right? Picked up a nice 2009 Outback 2.5i with 95k miles for a great price. Drives smooth, in great shape, the only problem, it throws a CEL for cylinder 1 and 2 misfire, but only at WOT near redline. It's also a pending fault, so the CEL doesn't stay current once out of WOT. The rest of the time it drives normal and smooth. Luckily I don't take the NA to redline much.

 

Incidental findings: The TPS sensor reads 14% at pedal up, and only 78% at WOT. It's the drive by wire throttle body and not adjustable that I know of.

 

Talking to the previous owner and looking at the Carfax, things seem to start to piece together.

 

7/2008 - 12/2011 - Only normal stuff reported, oil changes, title, etc

 

12/21/2011 - 26,000 miles - Minor accident to driver side fender

 

1/21/2012 - 26,248 miles - Fails emissions (pretty low mileage to fail emissions, a rational person could reason the CEL problem started here with the accident, although in Colorado you can fail emissions pretty easily for dumb stuff)

 

1/25/2012 - Passes emissions

 

2/29/2012 - Car sold to owner #2

 

6/2/2015 - 52,448 miles - Fuel injection system flushed at Grease Monkey

 

6/9/2015 - 52,630 miles - Induction system service at Subaru dealer (seems odd to do two fuel system services within a week, but then no more records for 4.5 years)

 

2/17/2020 - 82,952 miles - Car sold to owner #3, who purchases extended warranty

 

3/20/2020 - 83,467 miles - Engine is replaced for cylinder misfire, does not fix the issue (not listed in the Carfax, found this out by calling around). Also don't know if this was a shortblock with the rest swapped, or a full long block.

 

1/17/2021 - 95,000 miles - Owner CarMax's car with "major engine issues"

 

It seems this has been fuel system cleaner'ed to death, plus they replaced the engine with no change (crazy!). So what's left?

 

1) Voltage? Reading 13.8 with the car running, haven't looked at WOT.

 

2) Bad grounds? - I've pulled each and cleaned them, I'm going to replace the bottom two.

 

3) Fuel pressure? - haven't checked

 

4) Coil? - Have a spare I'll try, but it looks like someone may have put a new one on from how shiny the brass standoffs are. I can always check resistance on it. Has new plug wires and plugs.

 

5) MAF - I did pull it and clean it.

 

6) Damage to the bundle of wires in the driver's side fender during the accident? - I would think I'd see it more than just at WOT, but this seems plausible?

 

I guess I could also hook it up to a datalogger and log a pull when the CEL happens. I'll have to see if the cable for my '05 LGT works for this car too with the CANbus. What am I missing?

I've experienced injector failures on my 2.5 turbo. Depending what they replaced during the engine swap you could start there.

I thought about pulling them and having them cleaned. I'm starting with cleaning up all the grounds.

Have you swapped injectors from side to side and see if the CEL for the misfire follows ?

 

Don't 2.5i's have plug wires ? Have they been replaced ?

 

 

Back in 93' my 92 Civic has a slight misfire, the dealer had the car for three day's testing it with the "new diagnostic computer" plugged in driving it, and it showed nothing. Finally the mechanic went back to basics, took each plug wire off to test it with a meter, #1 plug wire was bad. Car was fine after that.

Edited March 26, 2021 by Max Capacity

The place I got it from did all new plug wires and coil by the looks of them. Seeing the history and seeing the engine was replaced, to no avail, has me going down slightly different paths than I normally would. It also has been injector cleanered to death from looking at the Carfax.

 

I've been pulling all the grounds, steel wooling them and hooking them back up with dielectric grease. So far since doing that I can't recreate the CEL. Not confident that fixed it, but cautiously optimistic. Would be crazy if they replaced the engine and ultimately sh*tcanned the car over a bad ground.

That would be funny and a plus for you.

 

Good Luck

Worth noting that our cars are old and injectors can leak with age. I got the ugly warning from Surgeline that my injectors appear to be heading out the door at 16 years old. A leaky injector will cause a misfire. In my car, you get the occasional WOT mild misfire or the really severe low speed misfire, as I've come to find the last couple days.

 

Try a vacuum leak test if you haven't. Or cross your fingers that the ground cleaning solved it! If you detached the battery at some point though, it probably will come back.

So I understood*this CEL wrong, at WOT it doesn't throw*a light, but at about 70-80%*pedal and kickdown it will throw a light for cyl 1 and 2 misfire.* Go easier (even with kickdown) or go WOT and it doesn't, so weird. And it's very intermittent, I went around beating on the car yesterday while logging, and it wouldn't throw the CEL no matter how much I tried. Edited March 28, 2021 by SSpeed

I would make sure all electrical connections are clean and tight.

 

Next would be a vacuum issue ?

 

Or may be check for a vacuum leak, can you pressurize the vacuum system and listen for leaks ?

 

Where is "apexi" he's good with 2.5i's

Thanks Max, I'm going to run a smoke test on it. I also ordered the bottom grounds and bolts to redo those as well.