CPAScott Posted February 7, 2011 Share Posted February 7, 2011 A few days ago a pulley for the serpentine belt broke in my 2005 Outback H6. I had it repaired straight-away, but the mechanic could not get a new belt. He advised changing it as soon as convenient when I picked the car up. Two days later the check engine light went on. I went to AutoZone to have the codes read and they noted multiple cylinders were misfiring -- particularly, cylinders 1, 3, and 5 along with some fuel/O2 mix issues and an O2 sensor heat issue, the latter two issues likely caused by the misfires. A return trip to the shop (a different one than the one who replaced the pulley and tensioner) ran full diagonstics on the car and noted the same issue, advising that the ignition coils needed replacement. At $150+ per coil plus labor, an expensive job. But these seems suspicious to me. Am I to believe that three ignition coils -- all on the exact same side of the engine -- all went out at the same time? Could it be causally related to the pulley breaking? Should I have the codes reset and see if they reappear? Have the work done? Take it to another mechanic for a 2nd opinion? Thoughts appreciated! Scott Quote Link to comment Share on other sites More sharing options...
naru Posted February 7, 2011 Share Posted February 7, 2011 Simultaneous failure of all the coils on one side seems unlikely to me too. An extra large splash of water making it past the spark plug well seals might be a better explanation. Did they make this diagnosis solely on the basis of misfire codes? What type of fuel/O2 mix issues did the codes show? It would be helpful to know exactly what the codes were. FYI,coils are $60 at Rockauto. Can`t see how the broken pulley would affect anything unless something was disturbed during the repair. How does it run? CEL still on? Vacuum leak or failed o2 sensor are possibilities. I advise seeking another opinion,resetting codes and noting exactly which come back. Quote Link to comment Share on other sites More sharing options...
Cougar Posted February 7, 2011 Share Posted February 7, 2011 (edited) I think your logic about the misfires causing the O2 sensor code may be backwards. My thinking is if you fix the O2 heater code issue the other troubles may clear up since the ECU uses data from the O2 sensor to determine the fuel mixture. The misfires also shouldn't effect the O2 heater circuit as far as I know. I also think a O2 heater code will go away as soon as the trouble has been fixed. Edited February 7, 2011 by Cougar Quote Link to comment Share on other sites More sharing options...
naru Posted February 7, 2011 Share Posted February 7, 2011 (edited) At least 98% chance you need to replace the o2 sensor to rectify the o2 sensor heater code. Good place to start.Not so sure a faulty o2 sensor heating element would cause the other problems,but just possible. Edited February 7, 2011 by naru Quote Link to comment Share on other sites More sharing options...
bheinen74 Posted February 7, 2011 Share Posted February 7, 2011 Did the mechanic set timing right? If a pulley bearing let go, it very well may have jumped. Does the mechanic know about Subaru interference engine, or what marks to use? Quote Link to comment Share on other sites More sharing options...
94Loyale Posted February 7, 2011 Share Posted February 7, 2011 The OP has a an H6, it was the serpentine belt pulley that broke. Not the idler pulleys on a 4cyl. I have very rarely seen those coils fail. If your shop immediately takes a misfire code as an excuse to replace 3 coils. Then your first step is to find a shop that knows what they are doing. 1,3,5 are on the same side of the motor, so i'd check for a loose connection somewhere. As far as the o2 heater code, that will prob not cause any problems you are going to notice. The heater only effects how quickly the car will go into closed loop. I'm curious about the o2/fuel mix issues also? Quote Link to comment Share on other sites More sharing options...
idosubaru Posted February 7, 2011 Share Posted February 7, 2011 i too would start with the thing you will have to replace anyway - the O2 sensor. clear and drive and see what returns. there's no way, except for a freak accident, that all three coils failed. so you didn't explicitly say it - but you had the serpentine pulley failure right? be advised - there are two pulleys both with the same bearings and both have frequent failures. the bearings are like $5 and easily replaceable - it takes literally a matter of minutes. i would have the other one replaced now if it wasn't. i replaced mine preemptively and they were not in great shape, glad i did. this is a really common failure on the H6's...but luckily it's really easy. i did both of mine for like $6 (i got the bearings cheap) and 20 minutes, it's really easy. Did the mechanic set timing right? If a pulley bearing let go, it very well may have jumped. Does the mechanic know about Subaru interference engine, or what marks to use?this is a timing chain. Quote Link to comment Share on other sites More sharing options...
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