1995SubaruImpreza Posted September 16, 2009 Share Posted September 16, 2009 Hi I was wondering if anyone could help me, my 2001 Subaru has been running very rough, slow acceleration and losing power. At an Idle it bucks and sputters, on the way home from work today (which I wasn't sure I was going to make it) I got a check engine light on and it is showing code P0170 and the code reader has a red light that comes on...Anyone know what is wrong? Oh I have run fuel injector cleaner through it, changed the fuel filter, spark plugs, air filter, and PCV valve. Quote Link to comment Share on other sites More sharing options...
Log1call Posted September 16, 2009 Share Posted September 16, 2009 That code says it is running too rich. Check the small rubber hose is attached to the fuel pressure regulator properly and that it has no holes or crack in it. Quote Link to comment Share on other sites More sharing options...
OB99W Posted September 16, 2009 Share Posted September 16, 2009 [...] it is showing code P0170 [...] The title of your thread is ''P0172'', but in the post you mention ''P0170''. Although there's some overlap of possible causes with those two codes (having to do with causes of excessive fuel pressure), knowing which is the correct one could lead to easier diagnosis, so please clarify. Also, can we assume we're discussing a Forester? How did the plugs you removed look -- were the firing tips sooty/blackened, tan/white, etc.? Is there any black smoke from the exhaust? Until we have more info, you could begin by checking for intake leaks and a ruptured fuel pressure regulator diaphragm (pull off its vacuum hose and see if there's any gas in it). Quote Link to comment Share on other sites More sharing options...
1995SubaruImpreza Posted September 16, 2009 Author Share Posted September 16, 2009 The title of your thread is ''P0172'', but in the post you mention ''P0170''. Although there's some overlap of possible causes with those two codes (having to do with causes of excessive fuel pressure), knowing which is the correct one could lead to easier diagnosis, so please clarify. Also, can we assume we're discussing a Forester? How did the plugs you removed look -- were the firing tips sooty/blackened, tan/white, etc.? Is there any black smoke from the exhaust? Until we have more info, you could begin by checking for intake leaks and a ruptured fuel pressure regulator diaphragm (pull off its vacuum hose and see if there's any gas in it). Sorry yes it is P0172, 2001 Subaru forester, the plugs look in pretty goods shape not burning/soot etc the on plug did have a bit of dried oil on it. Quote Link to comment Share on other sites More sharing options...
Log1call Posted September 16, 2009 Share Posted September 16, 2009 Get a compression check done. Put a vacumm gauge on and check the vacumm at idle is even(not fluctuating) and high, eighteen inches of vacumm is good. Quote Link to comment Share on other sites More sharing options...
1995SubaruImpreza Posted September 18, 2009 Author Share Posted September 18, 2009 The title of your thread is ''P0172'', but in the post you mention ''P0170''. Although there's some overlap of possible causes with those two codes (having to do with causes of excessive fuel pressure), knowing which is the correct one could lead to easier diagnosis, so please clarify. Also, can we assume we're discussing a Forester? How did the plugs you removed look -- were the firing tips sooty/blackened, tan/white, etc.? Is there any black smoke from the exhaust? Until we have more info, you could begin by checking for intake leaks and a ruptured fuel pressure regulator diaphragm (pull off its vacuum hose and see if there's any gas in it). I checked what I think is the hose is (very small hose) with the help my my hayne's manual it looks in good shape but where it connects there is no hose clamp and it slides on and off very easily Quote Link to comment Share on other sites More sharing options...
1995SubaruImpreza Posted September 18, 2009 Author Share Posted September 18, 2009 The title of your thread is ''P0172'', but in the post you mention ''P0170''. Although there's some overlap of possible causes with those two codes (having to do with causes of excessive fuel pressure), knowing which is the correct one could lead to easier diagnosis, so please clarify. Also, can we assume we're discussing a Forester? How did the plugs you removed look -- were the firing tips sooty/blackened, tan/white, etc.? Is there any black smoke from the exhaust? Until we have more info, you could begin by checking for intake leaks and a ruptured fuel pressure regulator diaphragm (pull off its vacuum hose and see if there's any gas in it). As for the exhaust no smoke or anything... Quote Link to comment Share on other sites More sharing options...
OB99W Posted September 18, 2009 Share Posted September 18, 2009 (edited) I checked what I think is the hose is (very small hose) with the help my my hayne's manual it looks in good shape but where it connects there is no hose clamp and it slides on and off very easily Any loose-fitting vacuum hoses and other possible intake leaks should be dealt with. As I mentioned before, if there is any sign of gas in the vacuum hose at the fuel pressure regulator, its diaphragm might have a hole. Possible causes of P0172 include excessive fuel pressure, intake temperature/pressure sensor problems, engine coolant temperature sensor failure, and even loose engine ground connections. In rare cases, a hole or loose connection in the exhaust system can ''confuse'' the oxygen sensor. If you don't have the experience to safely/carefully check those things yourself, I'd suggest taking the car to a good independent Subaru specialist, or the dealer. Edited September 18, 2009 by OB99W Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted September 18, 2009 Share Posted September 18, 2009 Does it do this as soon as it starts or only after it warms up? Could be a bad O2 sensor. How many miles on this car? Quote Link to comment Share on other sites More sharing options...
1995SubaruImpreza Posted September 20, 2009 Author Share Posted September 20, 2009 Does it do this as soon as it starts or only after it warms up? Could be a bad O2 sensor. How many miles on this car? Happens as soon as the car is turned on or within a minute or so. The car has 277,000kms I have had it since 198,000kms so I do not have the repair history on it before that. Since I have had it I have replaced the transmission, an axle, front output seal, and some other minor stuff like plugs wires etc Quote Link to comment Share on other sites More sharing options...
Log1call Posted September 20, 2009 Share Posted September 20, 2009 It might pay to concide that it could have a burnt valve or blown piston too at those miles and seeing as it's doing it right from cold. A compression test or putting a vacumm gauge on it might show you something interesting. Quote Link to comment Share on other sites More sharing options...
1995SubaruImpreza Posted September 23, 2009 Author Share Posted September 23, 2009 Hi Everyone, I just brought my car in the mechanic pulled the codes from it today and he said he got the same code as well as a code for a miss-fire on each of the cylinders and and one for the MAP sensor. So they cleaned the sensor and reinstalled this seemed to work but after about 15mins it started acting up again, so he is assuming it has shorted. He is suggesting replacing it, which is going to cost me about 600.00 with diagnostic time and parts and he is not sure if that will fix the problem. Has anyone experienced this, and does anyone know if it is likely to fix the problem. Also he said it is getting oil soaked because of oil blowby or something due to the mileage on the car (although he says it is not that bad). So if this is the case will it not just ruin the new sensor? I mentioned to him about a compression test but he said because the problem is intermittent the compression test would not be worth while. When he unplugged the sensor completely he said that the car has lots of power . Quote Link to comment Share on other sites More sharing options...
OB99W Posted September 23, 2009 Share Posted September 23, 2009 A compression test might reveal whether the rings are worn enough to be allowing excessive blow-by. However, given the sensor oil-contamination, taking another look at the PCV could be helpful. You mentioned changing the PCV valve in the first post of this thread -- was the replacement an OEM Subaru part, and did you make sure that the associated ''plumbing'' is all clear? Also, has the new air filter become oil-coated? Quote Link to comment Share on other sites More sharing options...
1995SubaruImpreza Posted September 25, 2009 Author Share Posted September 25, 2009 A compression test might reveal whether the rings are worn enough to be allowing excessive blow-by. However, given the sensor oil-contamination, taking another look at the PCV could be helpful. You mentioned changing the PCV valve in the first post of this thread -- was the replacement an OEM Subaru part, and did you make sure that the associated ''plumbing'' is all clear? Also, has the new air filter become oil-coated? The PCV valve I picked up at part source I think it was Fram, so no not a Subaru part. I got the car back today with the new MAP sensor and within about 15mins I didn't think it was going to make it back to the mechanics, but no check engine light. I asked about the compression test and the vacuum test again, and they have said the same thing that the problem is intermittent so they can not see how that can be the problem, also they checked the exhaust system and said it seems fine, I am not sure what they did. They cleaned the throttle plate..??? (I think that is term they used) They check the fuel pressure if I recall correctly they said it was 41 or 42 psi..??? I have left the car with them they are going to continue to work on it and see what they can do. I was wondering if anyone might be able to throw some more ideas on what they can check, they said they will do the compression test. As for the vacuum test what does that consist of? As for other bits of info. Fuel filter was changed about 3 weeks ago with what ever brand they carry at part source, I changed it and ran high grade gasoline with a bottle of injector cleaner through it. Spark plugs are NKG NGK (??) Platinum changed about 2 weeks ago The spark plug wires are Bosch changed about 6 months ago The transmission was changed out with a used one about 6-8 months ago Thanks everyone for all of your continued support! Quote Link to comment Share on other sites More sharing options...
OB99W Posted September 25, 2009 Share Posted September 25, 2009 They check the fuel pressure if I recall correctly they said it was 41 or 42 psi..??? Not being certain of the pressure or where it was measured makes it difficult to diagnose the problem. Typical fuel pressure from the fuel pump should be a bit higher than what you stated. However, it's important to check the fuel rail pressure, which should be about 32 psi if the regulator is working correctly. If it's too high there, the mixture could be too rich, resulting in P0172. Quote Link to comment Share on other sites More sharing options...
officerNordberg Posted October 6, 2009 Share Posted October 6, 2009 Any update on this? I'm having almost the exact same problem and I've tested or replaced many of the same things listed here and still the engine runs badly and I keep clearing a P0172 out of the computer. Quote Link to comment Share on other sites More sharing options...
Log1call Posted October 6, 2009 Share Posted October 6, 2009 The fuel pressure needs to be checked at idle to make sure the regulator is working, then again with the vacum hose off or the motor reving to be sure you have full pressure. As has been suggested, if the regulator has a hole in it's diaphram you will get high fuel pressure and a leak of fuel straight into the motor. The maf sensor is only one input to the ecu and should be over-ridden by the O2 sensor, so I'd doubt it is the cause, but it may contribute if the problem is a combination of factors. The small hose going to the fuel regulator... you say it's a loose fit, that could be letting the vacumm excape and that could do it. You don't actually say you have checked for fuel in that hose either... it may be a good idea to do that. If you could get it onto a laptop you could check what the IPW is like and that would help decide whether it's a sensor playing up or a fuel injector/regulator problem. Quote Link to comment Share on other sites More sharing options...
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