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Hi guys; haven’t been on here in a good while (life seems to do that with me. I just passed my first ASE test in brakes and have been busy doing that for a little while now. Anyway on to my issue. It’s my brothers car a 07 outback with the 2.5L N/A 5 speed with just about 110k on the clock. He purchased the vehicle a few months ago at a dealership and all was good until he had noticed cylinder 4 spark plug well full of oil; changed his drivers side valve cover and solved the issue. jump ahead about a month or two and he get’s a cel for a cylinder 2 misfire and since we had no record of his spark plugs being done we go ahead and do that; it solves the problem or so we thought; it’s been haunting us now for about a month and a half, and he’s been driving it like this for about the same time until he car started to become bogged down. My automotive mentor tipped me off to fuel supply being an issue. told me to check injectors and see if any of them have good spray pattern. Well I don’t have any tool to do that and we found out Napa will do that for you. So we pull all his injectors and have napa test them and rebuild/clean them up; in the mean time I decided to clean out his egr and that was just caked with carbon. We get the injectors back put everything back together and his subaru fires up better then it has been no misfire, idling normal for cold startup so we let it warm up on it’s own and we go for a little test drive. Everything seems normal and it happens again, his car stalls out releasing the gas pedal to come to a stop, runs real rough and acts like it’s towing the space shuttle. I am looking at the obdii data stream and don’t see anything that is out of the ordinary. He did tell me that he had run his car almost completely out of gas and that’s when he noticed the cylinder misfire and why we had Napa clean/rebuild his injectors. So it seems to happen when the car is at temp; a misfire on cylinder 2, very sluggish, and don’t want to accelerate. I don’t have any tools for a leak down test/compression test, I did check his coolant and it loorks normal. I can’t seem to figure this one out. Dealer said at time of test drive they did the timing belt but other then that absolutely no service history to speak of. Am I missing something pretty simple? I feel pretty stupid I can’t figure out my brothers car issue; I want to see him driving happily down the road in his ride that he absolutely loves. Any advice would be greatly appreciated because I can’t seem to figure this one out. Usually I can figure things out but this one is just stumping me. HELP!!!
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First place to start is to switch around anything related to spark, so switch around the wires or coils and check for signs of cracks in the boots. See if the misfire moves and replace parts accordingly. Pull the plug and check for signs of carbon tracking. Even thought hey are new, it is a possibility.
https://www.ericthecarguy.com/faq/solving-automotive-performance-issues
I forgot to mention we replaced plug wires too. Could it be possible a O2 sensor (upstream) could cause a miss? or could it be possible that the central coil is starting to go out and how would I go about testing the coil? I want to do as much diag as I can and not just fire off the parts canon.
Get yourself a spark tester and rig it up in line with the spark plug wire at the coil so that the spark still goes down and fires the spark plug. Watch and see if your spark starts to disappear when it starts misfiring.
Simply grab a bottle of something, I usually use a window cleaner as it’s usually available, spray down the coil pack and look for sparks. You don’t have to drench it, just a good mist on the outside to draw any stray current out. Then, if it’s dark you can simply look for stray sparking from the coil, use a screwdriver and move it around the coil, again looking for sparks. Or simply use a finger to ‘detect’ voltage leaking. Be warned, it will give you a decent zap but it won’t kill you.
The symptoms, to me, sound like its starving for fuel, rather than something with the spark.
Ran almost completely out of fuel? I’d honestly be looking at the fuel filter being filled with gunk and blocking the flow as a possibility. Same with the fuel pump pickup sock perhaps.
Another typical cause of suddenly running like crap after warming up could be the coolant temperature sensor, it has a pretty substantial influence on the quantity of fuel injected and can cause some very weird things if its borked. Is it repeatable (as in, after cooling down, does it run fine again?)
The computer is telling him he has a cylinder 2 misfire. there could be more but this is a 4 cylinder engine. If one cylinder is down then the engine will not run very well at all. I wouldn’t go chasing any wild geese. I would focus on that cylinder misfire and odds are when you fix that you will fix the other symptoms as well. Do the basics. you need spark, fuel, air and compression for that cylinder to work correctly. He needs to find out which one he is missing and trace that down.
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