October 7, 20178 yr I have a 2002 Legacy L with 200,000 on it that has been... abused, for lack of a better term. The PO let her boyfriend get his hands on it and, well.... anyway- runs ok for the most part. Has a new timing belt, new plugs and wires. I’ve set the valve lash and use good fuel but it has a misfire (cel code) when it’s idling at a light. Only thing I haven’t touched yet is the injectors. Looks like it may have a new TPS as well. The PO took of the cats but it still has the front O2 sensor. It is missing the second one though. Before I put any more money into it, need some ideas of where to start to diagnose the misfire. Any help is greatly appreciated.
October 8, 20178 yr plugs should be NGK - the cars can be picky about that. original plug wires could be bad - they also should be OEM. soobs will leak oil from bad valve cover gaskets on the plug wire boots causing misfires. have you scanned for pending codes? if your State inspection doesn't care, you can operate car-free with probably only a benign P0420 code. Edited October 8, 20178 yr by 1 Lucky Texan
October 8, 20178 yr Which cylinder(s)? Was it misfiring before you changed plugs? Swap plug wire from the misfiring cylinder with another. See if the misfire moves. Can do the same with a fuel injector if moving wires/plugs doesn't change it. Possibly a burned valve, a leak down test would tell.
October 8, 20178 yr We can help if we have car info, boyfriends and money can’t help us help you. I’m not trying to be a dork, just trying to drill down to information. When you say “misfire at a light” are you just guessing it’s a misfire or do you have codes or can you describe symptoms exactly? What do you mean “at idle” - what happens while driving? What code(s) does it have? How long before they come back if cleared? What brand plugs and wires? I’ve seen new wires cause misfires right out of the box on those engines if they’re cheap. Use NGK, OEM, Magnecor or something else documented good quality for subarus. How were the valves when you adjusted them? We’re they tight and which ones? Edited October 8, 20178 yr by idosubaru
October 8, 20178 yr Author We can help if we have car info, boyfriends and money can’t help us help you. I’m not trying to be a dork, just trying to drill down to information. When you say “misfire at a light” are you just guessing it’s a misfire or do you have codes or can you describe symptoms exactly? What do you mean “at idle” - what happens while driving? What code(s) does it have? How long before they come back if cleared? What brand plugs and wires? I’ve seen new wires cause misfires right out of the box on those engines if they’re cheap. Use NGK, OEM, Magnecor or something else documented good quality for subarus. How were the valves when you adjusted them? We’re they tight and which ones? When I am sitting at a light "at idle", it has a noticable misfire and the CEL starts blinking (indicating a misfire) when I am driving it seems to be fine and the blinking CEL goes away I will have to borrow my buddies reader so I know exactly what codes and what cylinder(s) for the misfire I haven't cleared the code(s) but the blinking goes away on its own. I have a constant CEL due to the missing O2 sensor Plugs are Bosch Platinum (I think) and not sure of the wires but changing both did nothing for the misfire When I did the valve lash, nothing was noticablly out of whack or tight so my guess is that the routine maintenance was kept up until a coulpe years ago when the boyfriend entered the picture. The car came from Michigan 2 years ago and I am the second owner. The girl who owned it originally, had all the maintenance done regular thanks to her fathers money Hopefully all that helps. My next step is the MAP sensor and then maybe the injectors unless someone has a better idea. I am a mechanic but this is my first Subaru. I've owned lots and lots of the air cooled VW's so I know the basics of boxer motors and I am not afraid to learn or get my hands dirty. Thanks again
October 8, 20178 yr get NGK copper core plugs (BKR6E11 is the recommended plug for this car) and either OEM or NGK (FX58) wires - these cars are fussy about plugs AND wires. aftermarket plugs & wires are known to be problematic (especially parts store wires) - just because it fits, does not mean it works well. also inspect the cam case covers (valve covers) for oil seepage - especially in the spark plug well - this is a common issue and easily fixed with new seals.
October 8, 20178 yr Author It had new NGK plugs in it when I switched to the Bosch ones. No change. I’ll try wires and cleaning the MAP sensor since that’s fairly easy. Valve covers have new seals since I did the valve adjustment but had no signs of leaks beforehand. I’ll have to get the gauges to do the compression test. Don’t have any on hand. Again, thanks for all the quick help. I’m sure I’ll get it worked out with y’alls help
October 8, 20178 yr 200K IS a lot of miles, compression test could save you time and money if bad - GenDis is a pro mechanic. if codes come back 1&2 or 3&4 - suspect coilpack , 'waste spark' ign. means cylinders share a coil. if they come should show 1&3 or 2&4, could be slipped timing though that is rare. Edited October 8, 20178 yr by 1 Lucky Texan
October 8, 20178 yr Author Timing could be the issue. The timing belt was replaced but only because it through the belt from a pulley going bad. I’ll double check that today. I didn’t even think to check that. I’ll pull codes today after church to see what cylinder(s) are misfiring and will post up my findings.
October 8, 20178 yr If it threw the belt then you most likely have one or more bent intake valves. Double check timing and then run compression test. GD
October 8, 20178 yr Author Just came from Autozone and the reader says misfire on cylinder 2 and 4. At speed (50-70mph) it runs perfect, just sitting at a light idling is when it seems to miss. I checked the timing marks and they seem to all line up at 12 o’clock like they should.
October 8, 20178 yr Author Just came from Autozone and the reader says misfire on cylinder 2 and 4. At speed (50-70mph) it runs perfect, just sitting at a light idling is when it seems to miss. I checked the timing marks and they seem to all line up at 12 o’clock like they should.
October 8, 20178 yr Likely bent intake valves on 2 and 4 due to the thrown belt. Check compression. GD
October 8, 20178 yr Author Yep. That’s the next step. Just gotta find the gauges to borrow or see if I can rent them
October 8, 20178 yr You can disable the crank position sensor and just listen to it crank or post a video of it cranking. It's obvious to the trained ear when compression is low in one or more cylinders. They crank like a dog running on three legs. You can also check amperage draw waveform on the starter, or use a pressure transducer hooked to the tailpipe and watch that waveform on a scope. Many methods. I can tell if an engine has uneven compression just cranking it. Takes me 30 seconds. Unplug crank sensor, crank engine. Tell customer bad news. GD
October 9, 20178 yr it through the belt.that makes this about as easy as diagnosis gets - it has bent valves. verify it first of course.
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now