svmaine Posted January 27, 2006 Share Posted January 27, 2006 Sorry for the long post but I think the history might be important. It's a '99 L, 176k miles on it. Here goes: A year ago the car started hesitating during acceleration and chk engine light came on, diag. said "misfire #3 cylinder". We replaced the plugs and wires, plug tips were black and engine ran perfect. This happened 2 more times in the span of a year and each time we replaced the plugs and wires and then it ran fine. The 3rd time however a few weeks after we replaced the plugs and wires the chk engine light remained on and I noticed one week that I had suddenly lost 100 miles per tank in mileage. Yes, I'm an anal engineer who calculates each tank . So I took it to the dealer and the computer read "bad air sensor and cat. converter not running at peak" or something like that:). I bought the sensor from the dealer and replaced it at home but forgot to disconnect the battery to reset the computer. The car immediately died after starting with the new sensor. We put the old sensor in and it ran fine. The next day we disconnected the battery, replaced the sensor and again it died, it would accelerate ok but as soon as you let it idle it died. So maybe a bad air sensor? We put the old one back in and this time it ran a bit rough while idling. So ordered another new sensor, disconnected the battery, replaced it and the car did the same thing. We put the old sensor back in and the car would idle for a minute then die, accelerating was fine till you let your foot off the gas. We gave up and brought it to a mechanic and he found a clogged cat. converter, it was glowing red right near the oxygen sensor. He cleared out the clog, ran it and it didn't immediately die but would die after 5-10 minutes of idling. He spent a week running it off and on to try and get a code and nothing came up. He replaced the oxygen sensor and still nothing came up. His thought is that the computer might need to be replaced? I've got a voicemessage into dear Tom and Ray for the show but haven't heard back from them yet. Any thoughts? Quote Link to comment Share on other sites More sharing options...
RallyKeith Posted January 27, 2006 Share Posted January 27, 2006 Have you done a compression test? I'm thinking maybe there is something wrong with a valve that isn't closing that is causing problems. If an exhaust valve in #3 isn't closing all the way it be causing the misfire, and it could be pushing excess raw fuel into the exhaust which would in turn overheat the cat and cause the clog. I would also think it would cause power loss and possible idle issues. Also hooking up a vaccum gauge to the intake manifold might be a good thing to do. This is of course just a WAG (Wild A$$ Guess) but for some reason it all came into my head. Keith Quote Link to comment Share on other sites More sharing options...
svmaine Posted January 27, 2006 Author Share Posted January 27, 2006 A compression test was also suggested on a different forum so I called the mechanic this morning and he is going to do one today. I mentioned about a possible valve problem but since when you accelerate the car sounds beautiful, no stalling, so he doesn't think there is anything wrong with the valves. He took another look in his Subaru book and now thinks that it might just be that the timing is off, I hope:)!! Quote Link to comment Share on other sites More sharing options...
RallyKeith Posted January 27, 2006 Share Posted January 27, 2006 A compression test was also suggested on a different forum so I called the mechanic this morning and he is going to do one today. I mentioned about a possible valve problem but since when you accelerate the car sounds beautiful, no stalling, so he doesn't think there is anything wrong with the valves. He took another look in his Subaru book and now thinks that it might just be that the timing is off, I hope:)!! Ignition timing is set and controlled by the ECU. If it is valve timing then either something went wrong like a weak tensioner. Did you recently have the timing belt replaced? I know they can be difficult to get all lined up if it's a DOHC. Keith Quote Link to comment Share on other sites More sharing options...
svmaine Posted January 27, 2006 Author Share Posted January 27, 2006 Actually I the timing belt has never been replaced, whoops. I've owned the car since 47k, bad, bad!! I think it is a SOHC. Hopefully I'll find out the results of the compression test by tomorrow. Quote Link to comment Share on other sites More sharing options...
Downbound Posted January 27, 2006 Share Posted January 27, 2006 A compression test was also suggested on a different forum so I called the mechanic this morning and he is going to do one today. I mentioned about a possible valve problem but since when you accelerate the car sounds beautiful, no stalling, so he doesn't think there is anything wrong with the valves. He took another look in his Subaru book and now thinks that it might just be that the timing is off, I hope:)!! Had the same problem with my 99 forester, turned out to be a burnt exhasut valve in #3 but you would have never known it from driving it..smooth, no hesitation..you could just hear a bit of a put put put from the exhaust when idling.. Quote Link to comment Share on other sites More sharing options...
svmaine Posted February 10, 2006 Author Share Posted February 10, 2006 Good news:banana: !! The timing belt had slipped a tooth so when my mechanic reset it the idling was much better. It now surges when idling but it doesn't die. I'm getting the belt replaced and hopefully that takes care of the surging. Now maybe I can finally sell it! Quote Link to comment Share on other sites More sharing options...
svmaine Posted February 13, 2006 Author Share Posted February 13, 2006 Can some of you Subaru Gods and Goddesses clear up some confusion:-\ ? I posted to a couple of other forums the same thing as above, that the timing belt slipped a tooth, and they are telling me that my mechanics throwing the wool over my eyes. According to them the engine wouldn't run if the belt had slipped a tooth and even if he did tighten it the idling problem would still happen. So my mechanic tells me that he replaced the timing belt and now it doesn't die anymore, just surges up and down. I had thought that yes with some engines, interference(?), if the timing belt slips the valves get crushed and engine doesn't run. But my engine isn't that type so is my mechanic being honest? Quote Link to comment Share on other sites More sharing options...
cookie Posted February 13, 2006 Share Posted February 13, 2006 Probably is. I have heard of a couple late model engines that were set up wrong and ran poorly. Retiming them cured the problem. This is lucky because if it is far enough off the valves can tangle and that is expensive. There is a reason they tell you to change the belt. Quote Link to comment Share on other sites More sharing options...
tunered Posted February 14, 2006 Share Posted February 14, 2006 something smells here,first off if its a soc off one tooth i dont think you would have enough power to test drive,secondly you still have about the same problem you had with less money in your pocket.does it drive out better now,after the belt job? Quote Link to comment Share on other sites More sharing options...
cookie Posted February 14, 2006 Share Posted February 14, 2006 Actually Ed changing cam timing has been a common speed trick for years. You don't go too far but that's what a degree wheel does. My BMW has a system called a vanos that constantly changes cam timing. A couple folks I know have screwed up the cam timing on late models and gooten away with it after fixing the timing. I understand they can run pretty poorly but still drive if you make the right mistake. I think I have also heard of folks screwing up so badly they bent a valve. Quote Link to comment Share on other sites More sharing options...
tunered Posted February 14, 2006 Share Posted February 14, 2006 Actually Ed changing cam timing has been a common speed trick for years. You don't go too far but that's what a degree wheel does. My BMW has a system called a vanos that constantly changes cam timing. A couple folks I know have screwed up the cam timing on late models and gooten away with it after fixing the timing. I understand they can run pretty poorly but still drive if you make the right mistake. I think I have also heard of folks screwing up so badly they bent a valve. cookie.i understand the cam timing,i was really wanting to know how well it ran before the new belt and if it ran better after the belt fix,i bet it didnt change anything.i really believe the valve is burnt letting raw fuel thru to the cat plugging it up. dont understand the o2 sensor change making the engine stall. Quote Link to comment Share on other sites More sharing options...
tunered Posted February 14, 2006 Share Posted February 14, 2006 cookie,went back and read the first post,he said the mech found a plugged cat and cleared the plug,that means to me he took a pipe thru the cat and knocked some out,probally the same problem he started with. Quote Link to comment Share on other sites More sharing options...
cookie Posted February 14, 2006 Share Posted February 14, 2006 Could be Ed. Pretty hard when you can't see it. A new belt may make it run better and I'm sure its needed regardless. I wonder about the tensioner too as if it slipped why did it? Quote Link to comment Share on other sites More sharing options...
2.5GL Posted February 14, 2006 Share Posted February 14, 2006 The engine will run with the belt off a tooth or two, badly. AND not crash the valves. more than two teeth and you would be a little less lucky, and would be very difficult to run not to mention drive. If it continues to hunt for an idle speed let it run with the AC on for 5-10 minutes then turn off AC and go for another 10. Forgot:D ...clear the memory first or disconnect battery (I'm guessing...1 hour? I have an ODB II meter, so can't say how long.) If it doesn't settle down, might want to go after your IAC (idle air control) for idling prob. of air flow meter for off idle response. Quote Link to comment Share on other sites More sharing options...
svmaine Posted February 15, 2006 Author Share Posted February 15, 2006 Latest update is that it runs perfect, no surging, no dying, with the new timing belt. $500 later I think I learned my lesson about changing the timing belt. I asked the mechanic about why the valves didn't get smashed and he confirmed that it isn't an interference engine, phew! So anyone interested in buying it:) ??!! I hate to get rid of my dear Forester but need to sell it quick to pay for my "new" van. Quote Link to comment Share on other sites More sharing options...
svmaine Posted February 15, 2006 Author Share Posted February 15, 2006 P.S. Not that it really matters but Tunered if you want to use the correct pronoun, change your he to she:D, and thanks for posting! Quote Link to comment Share on other sites More sharing options...
cookie Posted February 15, 2006 Share Posted February 15, 2006 If it has the stock engine I think it would be interference. There is much confusion on this issue, but as far as I know all the late models are. With just one tooth off it would run poorly but would be unlikly to clash valves. Quote Link to comment Share on other sites More sharing options...
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