subegrl Posted August 2, 2007 Share Posted August 2, 2007 2001 Forester, 172k miles. I wrote in recently saying that I thought I might need a catalytic converter, because my car was intermittently acting starved for gas. It was suggested that it might be an 02 sensor instead, as it had thrown the p0420 code before in the past... meanwhile the check engine light was going on intermittently, too. It would stay lit for a day or two then go away... I left it at my mechanic's and surprise, it didn't do any of the lurching, hesitation, I-need-gasoline that it had been doing all weekend. The CEL was not on but the computer showed a history of p0328 - knock sensor. I had replaced this sensor a couple of months ago. I had also replaced the fuel filter last winter. He replaced the fuel filter again, and asked me to drive the car over to him while it is doing it's 'thing' to try to get a decent diagnosis. But I can't do that, it seems, because the problem is almost gone - almost. None of this makes sense to me. Should I go ahead and replace the front 02 sensor anyway? Link to comment Share on other sites More sharing options...
uniberp Posted August 2, 2007 Share Posted August 2, 2007 2001 Forester, 172k miles.I wrote in recently saying that I thought I might need a catalytic converter, because my car was intermittently acting starved for gas. It was suggested that it might be an 02 sensor instead, as it had thrown the p0420 code before in the past... meanwhile the check engine light was going on intermittently, too. It would stay lit for a day or two then go away... I left it at my mechanic's and surprise, it didn't do any of the lurching, hesitation, I-need-gasoline that it had been doing all weekend. The CEL was not on but the computer showed a history of p0328 - knock sensor. I had replaced this sensor a couple of months ago. I had also replaced the fuel filter last winter. He replaced the fuel filter again, and asked me to drive the car over to him while it is doing it's 'thing' to try to get a decent diagnosis. But I can't do that, it seems, because the problem is almost gone - almost. None of this makes sense to me. Should I go ahead and replace the front 02 sensor anyway? I get an occasional 'bucking' (usually just one 'buck') when the car is loaded at highway speed. The knock sensor was replaced some time ago, but I am considering moving it to a different location to minimize the effect. Another test would be to simply run premium gas. That should knock less. The repeated references (here) to how much fuel additives/injector cleaners (seafoam, Techron) improve performance, seem to me that they simply reduce knock enough to reduce timing retardation. At least for THAT tank of gas. ?? Link to comment Share on other sites More sharing options...
subegrl Posted August 2, 2007 Author Share Posted August 2, 2007 I get an occasional 'bucking' (usually just one 'buck') when the car is loaded at highway speed. The knock sensor was replaced some time ago, but I am considering moving it to a different location to minimize the effect. Another test would be to simply run premium gas. That should knock less. The repeated references (here) to how much fuel additives/injector cleaners (seafoam, Techron) improve performance, seem to me that they simply reduce knock enough to reduce timing retardation. At least for THAT tank of gas. ?? Well, I haven't run premium gas in it in a long long time, so I will run a tank thru and see if that last bit of hesitation goes away. Strange thing is I usually run a bottle of Techron in it every oil change and so I would think that would remove fuel related problems. Link to comment Share on other sites More sharing options...
idosubaru Posted August 2, 2007 Share Posted August 2, 2007 was the knock sensor replaced with a new one or a used one? was it tightened properly, that would be a good component to make sure is torqued to spec. Link to comment Share on other sites More sharing options...
subegrl Posted August 2, 2007 Author Share Posted August 2, 2007 was the knock sensor replaced with a new one or a used one? was it tightened properly, that would be a good component to make sure is torqued to spec. new one. I can check and see if it is loose. good suggestion! Link to comment Share on other sites More sharing options...
uniberp Posted August 2, 2007 Share Posted August 2, 2007 Well, I haven't run premium gas in it in a long long time, so I will run a tank thru and see if that last bit of hesitation goes away.Strange thing is I usually run a bottle of Techron in it every oil change and so I would think that would remove fuel related problems. Do you notice the hesitation when you have techron in the tank? That's kind of my point. Fuel additives, even those that are supposedly just cleaners, may reduce knock. Link to comment Share on other sites More sharing options...
subegrl Posted August 2, 2007 Author Share Posted August 2, 2007 Do you notice the hesitation when you have techron in the tank? That's kind of my point. Fuel additives, even those that are supposedly just cleaners, may reduce knock. No, but then again, it's been 3 months since I put the Techron in... I just got my oil changed last week when they were researching the hesistation so I could put some Techron in again, however do you think that's mudding up the problem by adding another element to it? Link to comment Share on other sites More sharing options...
subegrl Posted August 3, 2007 Author Share Posted August 3, 2007 hmmm, checked the knock sensor, it is not loose. Link to comment Share on other sites More sharing options...
subegrl Posted August 6, 2007 Author Share Posted August 6, 2007 Put techron and premium gas in it. Drove out of state and back. Still have the problem. Still intermittent. A friend was insistent that it *had* to be my catalytic converter, because his (nissan truck) had the same symptoms. However, after I got home I thought about it. My gas mileage has not suffered. Wouldn't a clogged converter kill my gas mileage? Link to comment Share on other sites More sharing options...
Manarius Posted August 6, 2007 Share Posted August 6, 2007 A clogged cat would produce a pungent smell you couldn't miss. Link to comment Share on other sites More sharing options...
subegrl Posted August 6, 2007 Author Share Posted August 6, 2007 A clogged cat would produce a pungent smell you couldn't miss. for real?!?!? Because I haven't noticed any weird smells... Link to comment Share on other sites More sharing options...
Cougar Posted August 6, 2007 Share Posted August 6, 2007 I would guess the occassional bucking may be due to the fuel pump. It could also be the plugwires causing this problem. Link to comment Share on other sites More sharing options...
uniberp Posted August 6, 2007 Share Posted August 6, 2007 Put techron and premium gas in it. Drove out of state and back. Still have the problem. Still intermittent.A friend was insistent that it *had* to be my catalytic converter, because his (nissan truck) had the same symptoms. However, after I got home I thought about it. My gas mileage has not suffered. Wouldn't a clogged converter kill my gas mileage? Maybe to clarify: is it 'bucking' or 'bogging' or ??? The Legato bogs down at 2.2k-2.6k rpm and I have been through the same series of fixes you have with no real improvement. I get very good gas mileage 25city-full30highway. I'm thinking now about fuel pressure. A techsheet suggested the fuel filter, which I'll now check/change. If fuel pressure is at the low end of the permissible range, it may cause a lean/ping/knocksensor triggering and retard timing condition. 145k miles on this one. Link to comment Share on other sites More sharing options...
subegrl Posted August 6, 2007 Author Share Posted August 6, 2007 Maybe to clarify: is it 'bucking' or 'bogging' or ??? The Legato bogs down at 2.2k-2.6k rpm and I have been through the same series of fixes you have with no real improvement. I get very good gas mileage 25city-full30highway. I'm thinking now about fuel pressure. A techsheet suggested the fuel filter, which I'll now check/change. If fuel pressure is at the low end of the permissible range, it may cause a lean/ping/knocksensor triggering and retard timing condition. 145k miles on this one. Sometimes bogging, sometimes bucking. Mostly on hills. Can be a smooth upward gradient, not just a steep hill. I think the suggestion to check the fuel pressure is a good one. I did have them change the fuel filter, and there was some improvement I think, but it's so hard to say definitively with a problem that is intermittent. I haven't had the plug wires changed in 73k. But I did run the car at night and lift the hood to see if I saw any sparking, and I did not. Link to comment Share on other sites More sharing options...
OB99W Posted August 6, 2007 Share Posted August 6, 2007 http://endwrench.com/images/pdfs/07FebFuelEW.pdf http://endwrench.com/images/pdfs/FeedNov06EW.pdf Link to comment Share on other sites More sharing options...
uniberp Posted August 6, 2007 Share Posted August 6, 2007 Sometimes bogging, sometimes bucking. Mostly on hills. Can be a smooth upward gradient, not just a steep hill. I think the suggestion to check the fuel pressure is a good one. I did have them change the fuel filter, and there was some improvement I think, but it's so hard to say definitively with a problem that is intermittent. I haven't had the plug wires changed in 73k. But I did run the car at night and lift the hood to see if I saw any sparking, and I did not. I just did a search on this board on "MAF Bogging" and I'm going to try cleaning the MAF with come of that CRC Electronics cleaner tonight. Link to comment Share on other sites More sharing options...
subegrl Posted August 6, 2007 Author Share Posted August 6, 2007 I just did a search on this board on "MAF Bogging" and I'm going to try cleaning the MAF with come of that CRC Electronics cleaner tonight. Where do I find the MAF on a 2001 Forester? That certainly seems worth a try - what have I got to lose? Link to comment Share on other sites More sharing options...
montana105 Posted August 6, 2007 Share Posted August 6, 2007 This almost sounds like a classic fuel pump/heat related problem.Your car has lots of mileage in a short time.Does the symptoms appear in warmer weather on hotter roads? Or does it matter the conditions? In hotter weather with my American cars with higher mileage where the road surface is very hot I have experienced intermittent fuel pump pressure irregularities,on one car it was to the point where on a hot summer day,hot pavement the fuel pump would cut out car would die and I'd coast it to the side of the road,had to wait 30 + minutes for the fuel in the tank to cool down,car would fire up and run great for an hour.Managed to limp it into the dealership and cough up 500.00 for a new pump + labor. This isn't just an isolated incident and not just American cars,I've had it happen to both American and Imports,it is a definite problem with high mileage fuel pumps in tank,at least with passenger cars as their tanks sit close to the pavement/asphalt and cause the fuel to boil,swelling the venturies of the pump.Don't get me wrong as the in take pumps last a lot longer then then old style mechanical pumps.But it is very hard for a mechanic to check fuel pressure on a pump that only acts up under stress and after sitting all night. Link to comment Share on other sites More sharing options...
subegrl Posted August 6, 2007 Author Share Posted August 6, 2007 This almost sounds like a classic fuel pump/heat related problem.Your car has lots of mileage in a short time.Does the symptoms appear in warmer weather on hotter roads? Or does it matter the conditions? Those are good questions, and I don't know the answers, because it's the middle of summer. However my suspicion is that the conditions outside are not a factor. Week before last, for instance, it rained several days in a row, which I would think would make the pavement/asphalt cooler, and the car had the same intermittent problems it has now. In hotter weather with my American cars with higher mileage where the road surface is very hot I have experienced intermittent fuel pump pressure irregularities,on one car it was to the point where on a hot summer day,hot pavement the fuel pump would cut out car would die and I'd coast it to the side of the road,had to wait 30 + minutes for the fuel in the tank to cool down,car would fire up and run great for an hour.Managed to limp it into the dealership and cough up 500.00 for a new pump + labor. This isn't just an isolated incident and not just American cars,I've had it happen to both American and Imports,it is a definite problem with high mileage fuel pumps in tank,at least with passenger cars as their tanks sit close to the pavement/asphalt and cause the fuel to boil,swelling the venturies of the pump.Don't get me wrong as the in take pumps last a lot longer then then old style mechanical pumps.But it is very hard for a mechanic to check fuel pressure on a pump that only acts up under stress and after sitting all night. I need to ask my mechanic if he checked the fuel pressure. I am perfectly willing to replace the fuel pump or catalytic converter or whatever... it's true my car has a lot of miles on it in a short time, but they are highway miles... Link to comment Share on other sites More sharing options...
Manarius Posted August 6, 2007 Share Posted August 6, 2007 Bucking is almost always associated with MAF troubles. Link to comment Share on other sites More sharing options...
nipper Posted August 7, 2007 Share Posted August 7, 2007 At 172,000 miles on the OE O2 sensor is a long long time. The sensor is near the end of its life (anything after 100,000 miles is cream). When blu hit 180,000 he got a tuneup and a new O2 sensor, It stopped the angry light from coming on and got rid of my bucking. nipper Link to comment Share on other sites More sharing options...
jon38iowa Posted August 7, 2007 Share Posted August 7, 2007 Put techron and premium gas in it. Drove out of state and back. Still have the problem. Still intermittent.A friend was insistent that it *had* to be my catalytic converter, because his (nissan truck) had the same symptoms. However, after I got home I thought about it. My gas mileage has not suffered. Wouldn't a clogged converter kill my gas mileage? Another way to tell if your Converter is toast is: A minute or two after starting the car, reach under and feel(or close to its surface) the converter. It should be hot, regardless whether the rest of the exhaust system is or not. If not, then chances are its seen better days. Link to comment Share on other sites More sharing options...
nipper Posted August 7, 2007 Share Posted August 7, 2007 Another way to tell if your Converter is toast is: A minute or two after starting the car, reach under and feel(or close to its surface) the converter. It should be hot, regardless whether the rest of the exhaust system is or not. If not, then chances are its seen better days. nononononono If he has a malfunctioining FI system, and the converter is running hot, he can get burned. nipper Link to comment Share on other sites More sharing options...
Manarius Posted August 7, 2007 Share Posted August 7, 2007 Like I said before, a bad cat would give off an odor nobody could miss. There's no reason to be reaching under the car in the chance of burning yourself. Link to comment Share on other sites More sharing options...
subegrl Posted August 7, 2007 Author Share Posted August 7, 2007 At 172,000 miles on the OE O2 sensor is a long long time. The sensor is near the end of its life (anything after 100,000 miles is cream). When blu hit 180,000 he got a tuneup and a new O2 sensor, It stopped the angry light from coming on and got rid of my bucking. nipper I think this is the 3rd or even 4th 02 sensor on my car. I looked in my Haynes Subaru repair book last night and it didn't list where the MAF sensor is. Anyone know where that is on an 01 Forester? Ah - did a search - I bet it has a MAP not a MAF. Link to comment Share on other sites More sharing options...
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