friendly_jacek Posted March 11, 2005 Share Posted March 11, 2005 2000 legacy, no codes, O2 sensor works fine, but the mixture is super rich with cold engine, terrible smell of unburn hydrocarbons and 16 MPG on short trips. 4% gas in oil after some idling. I understand that subaru engines tend to run rich but this is too much. Is there a way to adjust somehow? How? Thanks! Quote Link to comment Share on other sites More sharing options...
Setright Posted March 11, 2005 Share Posted March 11, 2005 Coolant temp sensor? Quote Link to comment Share on other sites More sharing options...
friendly_jacek Posted March 11, 2005 Author Share Posted March 11, 2005 Coolant temp sensor? No, I checked it with OBD2 interface, the temp it reads is real, both in cold and hot conditions. Thanks anyway. Quote Link to comment Share on other sites More sharing options...
frag Posted March 11, 2005 Share Posted March 11, 2005 2000 legacy, no codes, O2 sensor works fine, but the mixture is super rich with cold engine, terrible smell of unburn hydrocarbons and 16 MPG on short trips. 4% gas in oil after some idling. I understand that subaru engines tend to run rich but this is too much. Is there a way to adjust somehow? How? Thanks! How cold is it where you are? I always get about the same mileage as your's in the deep of winter for short city trips. Since I get 30 miles to the US gallon on highway trips during the summer and with same settings, I put that on the climate conditons and on the kind of driving I do during the winter. Curious: how did you measure oil's fuel content so precisely? Quote Link to comment Share on other sites More sharing options...
friendly_jacek Posted March 11, 2005 Author Share Posted March 11, 2005 How cold is it where you are? I always get about the same mileage as your's in the deep of winter for short city trips. Since I get 30 miles to the US gallon on highway trips during the summer and with same settings, I put that on the climate conditons and on the kind of driving I do during the winter. Curious: how did you measure oil's fuel content so precisely? Well, it's alabama, so not that cold (freezing once, maybe twice a year :-) Fuel in oil content is a part of every standard oil analysis. I did the analysis in part to prove the problem to the dealer under warranty. Those "factory trained" idiots never ever heard of oil analysis. Now, the car is out of warranty, so I can play with the engine a little, just don't know where to start. To summarize, close loop operation is fine, it is the open loop I am concerned about. Quote Link to comment Share on other sites More sharing options...
mtsmiths Posted March 11, 2005 Share Posted March 11, 2005 Well, it's alabama, so not that cold (freezing once, maybe twice a year :-)Fuel in oil content is a part of every standard oil analysis. I did the analysis in part to prove the problem to the dealer under warranty. Those "factory trained" idiots never ever heard of oil analysis. Now, the car is out of warranty, so I can play with the engine a little, just don't know where to start. To summarize, close loop operation is fine, it is the open loop I am concerned about. If this is a continuing problem not resolved when you made record under warranty, it will still be covered ... if the monkeys can figure out what's wrong - or you can tell them. Quote Link to comment Share on other sites More sharing options...
blitz Posted March 11, 2005 Share Posted March 11, 2005 To summarize, close loop operation is fine, it is the open loop I am concerned about. Check your fuel pressure. If your regulator's malfunctioning or it's vaccum line is dissconnected it'll give a high fuel-pressure rich condition when the engine's running on the fixed map. The closed-loop operation can compensate up to a point although if the pressure gets too high the injectors cease to function properly. Quote Link to comment Share on other sites More sharing options...
friendly_jacek Posted March 12, 2005 Author Share Posted March 12, 2005 Check your fuel pressure. If your regulator's malfunctioning or it's vaccum line is dissconnected it'll give a high fuel-pressure rich condition when the engine's running on the fixed map. The closed-loop operation can compensate up to a point although if the pressure gets too high the injectors cease to function properly. Thanks Blitz, Is there an easy way to check the pressure? ECU does not report one via OBD2 and I don't see any pressure measuring ports on fuel line. This is SOHV phase 2 2.5L H4. Quote Link to comment Share on other sites More sharing options...
blitz Posted March 12, 2005 Share Posted March 12, 2005 Thanks Blitz,Is there an easy way to check the pressure? ECU does not report one via OBD2 and I don't see any pressure measuring ports on fuel line. This is SOHV phase 2 2.5L H4. Yeah the fact that the ECU doesn't monitor that parameter would explain why it didn't or couldn't throw a code for it. You'll need to tap in a fuel pressure meter. The point where the fuel line exits the filter is a good spot. The regulator allows system pressure to build by restricting return flow back to the tank. Conversely, the more it opens, the more return flow it allows and the more fuel pressure drops. It's pretty simple. It doesn't actually adjust the pressure on the fly, but rather holds it at a fixed value RELATIVE TO MANIFOLD VACCUM (not atmospheric). It tracks the conditions inside the intake manifold, that's why it's referenced to the intake manifold by a vaccum line. In other words, if the spec fuel pressure is 40 psi., then the regulator maintains the fuel pressure at 40 psi above intake manifold value. First you might just want to check the vaccum line to the regulator to make sure it's actually connected at both ends and intact (not cracked anywhere). Also with the engine off you can apply suction (with your mouth) to the regulator to check it's diaphram for integrity. You shouldn't be able to draw air by sucking. If you can, then it's punctured or cracked and needs to be replaced. Quote Link to comment Share on other sites More sharing options...
Setright Posted March 13, 2005 Share Posted March 13, 2005 Top quality analysis, Blitz! Quote Link to comment Share on other sites More sharing options...
SevenSisters Posted March 13, 2005 Share Posted March 13, 2005 How short is a "short" trip? I'm leaning with Frag on this one but not ruling out the other suggestions like fuel pressure you've received. Unless you're driving more than ten miles at a crack, 16 mpg and 4% gas in your oil wouldn't surprise me. Fill it up, take a nice Sunday drive on the interstate at the speed limit for about 300 miles, say hello to the tire guys in Cullman, and re-fill it. If you don't get about 26-27 mpg, get serious about the condition. I had poor mileage and the worst tail pipe odor you could imagine, kind of like wet, buring straw, that eventually (about a month) caused cylinder #3 to go out (not fire) and throw a fuel injector code. Replacement of the injector eliminated the problem and what I assume to be excessive gas into cylinder #3. If you're not driving much, a can of Seafoam or Techron may help. Quote Link to comment Share on other sites More sharing options...
blitz Posted March 13, 2005 Share Posted March 13, 2005 Top quality analysis, Blitz! Humble thanks. My one overwhelming characteristic is a sponge-like affinity for knowing stuff, laid-out in a practical way. I hate verbose, confusing, technical descriptions. My other overwhelming characteristics are an affinity for beer and cynicism. Quote Link to comment Share on other sites More sharing options...
friendly_jacek Posted March 14, 2005 Author Share Posted March 14, 2005 Humble thanks. My one overwhelming characteristic is a sponge-like affinity for knowing stuff, laid-out in a practical way. I hate verbose, confusing, technical descriptions. My other overwhelming characteristics are an affinity for beer and cynicism. Blitz, you're da man! I will check the pressure today when I get ahold of a gauge. I totally makes sense for that to be excessive. The ECU reports -11% long term fuel trim. Meaning that computer substracts 11% fuel to make the O2 sensors happy. Obviously, in open loop, the engine gets the excessive 11% fuel. Since all sensors work fine (it is so much easier to test MAP vs. MAF!), this points to fuel delivery. SevenSisters, The 16 MPG is with trips less than 10 miles, more like 3-4 miles or so (my wife has a short commute). But it used to be more like 20 when the car was new. Furthermore, I never got more than 25 MPG, even with pure, long distance hwy trips. I used techron and redline injector cleaners on many occasions. If the fuel pressure is correct, I will go after the injectors. Quote Link to comment Share on other sites More sharing options...
Setright Posted March 16, 2005 Share Posted March 16, 2005 Blitz: Mmmmmm, BEER! Quote Link to comment Share on other sites More sharing options...
friendly_jacek Posted March 19, 2005 Author Share Posted March 19, 2005 And the prize goes to Blitz. The pressure read 42/52 psi with/without vacum, respectively. According to my source, normal is 30-34/41-46 psi. I am going shoping for new fuel regulator. Attn: people with poor MPG and no ECU codes but negative long term fuel trim, check your pressure! Quote Link to comment Share on other sites More sharing options...
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