subihoot03 Posted June 5, 2007 Share Posted June 5, 2007 So, yesterday I brought my car to the mechanic to investigate a misfire on one of my cylinders. This is a 2003 Subaru Legacy L, approx 103K. Mechanic tells me it's the plug wires, replaces those, gives it an oil change and sends me on my way. Backstory: I had been noticing poor gas mileage (in the 13-14 mpg range) and a slight miss when coasting, up until the time when my check engine light finally came on. As soon as I got the car back, I was thrilled - the slight hesitation was gone and the engine was running smoother than I have ever felt it run. However, it's too soon to tell if the plug wires have taken care of my mileage issue. This morning, I got into my car and started it so I could embark upon my commute. The idle suddenly dropped as quickly as it had peaked and the engine cut. I looked at the instrument panel in confusion, waited about ten seconds, and turned the key again. The car fired up just fine, but the tachometer needle was jumping in the 1500-2000 RPM range. I put the car in reverse, backed out and noted the faint smell of gasoline as I did this (the smell disappeared within seconds of me leaving my driveway, but sometimes these things bear mentioning). Has anyone else ever had a similar issue? Or am I just an auto-hypochondriac, noticing every little idiosyncracy my car has...? Help? Quote Link to comment Share on other sites More sharing options...
Legacy777 Posted June 6, 2007 Share Posted June 6, 2007 bump Quote Link to comment Share on other sites More sharing options...
porcupine73 Posted June 6, 2007 Share Posted June 6, 2007 If the battery was disconnected when the plug wires were replaced, it may not have relearned its idle parameters yet. Also Suby's tend to like their own OEM wires best. After it cut out and you restarted, it may have increased the fuel a little bit if it thought it died because of a lean condition. I can usually smell a little raw fuel on my Suby's at startup if I'm by the tailpipe but not too much. There are many things that can cause poor fuel economy. If you're still on your original front o2 sensor at 103k, you might consider replacing it since it's likely near the end of it's useful life anyway. Suby's like their own OEM front o2 sensors too. Of course, you're nearing 105k miles too, which means you're due for a timing belt replacement if not already done (unless you have the H6 engine...). Quote Link to comment Share on other sites More sharing options...
subihoot03 Posted June 19, 2007 Author Share Posted June 19, 2007 If the battery was disconnected when the plug wires were replaced, it may not have relearned its idle parameters yet. Also Suby's tend to like their own OEM wires best. After it cut out and you restarted, it may have increased the fuel a little bit if it thought it died because of a lean condition. I can usually smell a little raw fuel on my Suby's at startup if I'm by the tailpipe but not too much. There are many things that can cause poor fuel economy. If you're still on your original front o2 sensor at 103k, you might consider replacing it since it's likely near the end of it's useful life anyway. Suby's like their own OEM front o2 sensors too. Of course, you're nearing 105k miles too, which means you're due for a timing belt replacement if not already done (unless you have the H6 engine...). Hi Porcupine! Thanks for your reply - sorry it took me so long to confirm its receipt. I am going to have the o2 sensor looked into. The mileage is still suffering something wicked, and I notice a faint burning smell of indeterminate origin whilst climbing hills sometimes. It *almost* smells like burning oil, but this car isn't using a whole lot of oil right now. I'm still getting somewhere in the range of 15-17 mpg, combined city/highway...with lots of hill climbing. Timing belt was replaced at 96K when I bought the car. I insisted that it get replaced before I bought the car, because even though Subaru likes to push the 105K marker I thought it best to take care of it way before hand. I'm really not sure if the o2 sensor is original but all bets say it is! Also, I've noticed that the misfire is still probably present. The engine isn't throwing any codes right now but I do still get a slight "chugging" if I let off the throttle to coast down a hill. This Subi is quickly becoming my expensive but loveable problem child!!! Thanks again...your reply was very very helpful to me. Quote Link to comment Share on other sites More sharing options...
porcupine73 Posted June 19, 2007 Share Posted June 19, 2007 How does the vehicle run overall? I mean does it seem to have reasonable power and smoothness or is it struggling? Maybe this mileage isn't too unreasonable if you're climbing a lot of hills. When you come down the hills, are you having to brake and/or downshift? Quote Link to comment Share on other sites More sharing options...
subihoot03 Posted June 21, 2007 Author Share Posted June 21, 2007 How does the vehicle run overall? I mean does it seem to have reasonable power and smoothness or is it struggling? Maybe this mileage isn't too unreasonable if you're climbing a lot of hills. When you come down the hills, are you having to brake and/or downshift? It does seem to have reasonable power, and it usually runs well. It doesn't idle rough or anything. It's not too terribly sluggish - sometimes I do have a little difficulty on really steep grades maintaining speed. It is an AT so I'm not having to downshift but I usually do end up braking. I know that's probably not HELPING my gas mileage any! Quote Link to comment Share on other sites More sharing options...
porcupine73 Posted June 21, 2007 Share Posted June 21, 2007 Ok. Since you mentioned timing belt I was just wondering if the timing belt was off a tooth but doesn't sound like it. Quote Link to comment Share on other sites More sharing options...
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