YeuEmMaiMai Posted February 23, 2018 Author Share Posted February 23, 2018 driving the car over the last few days I am still at 21-22mpg mixed... this is beyond ridiculous Link to comment Share on other sites More sharing options...
laz Posted February 23, 2018 Share Posted February 23, 2018 driving the car over the last few days I am still at 21-22mpg mixed... this is beyond ridiculous Are you checking at the gas pump or going by the MPG computer? --- Link to comment Share on other sites More sharing options...
dgoodhue Posted February 23, 2018 Share Posted February 23, 2018 It doesn't sound like the dealer did anything, so your results aren't that surprising. Link to comment Share on other sites More sharing options...
YeuEmMaiMai Posted February 23, 2018 Author Share Posted February 23, 2018 Are you checking at the gas pump or going by the MPG computer? I do it by the math method... with that said. the MPG indicator is typically off by about .3MPG as I have gone into the cluster and adjusted it Link to comment Share on other sites More sharing options...
nads Posted February 24, 2018 Share Posted February 24, 2018 You might post your longs, some folks here are pretty savvy with looking at them, extra eyes can't hurt. Its interesting you bring up MAF signal issues. Have you looked into Vacuum leaks? Lean condition can cause cold running. Do you have surging idle at all? Sluggish response? Have the spark plugs ever been out? A loose plug(s) could cause some of these issues. Link to comment Share on other sites More sharing options...
YeuEmMaiMai Posted February 24, 2018 Author Share Posted February 24, 2018 I have not smoked the car yet but I am certain it is MAF... Thursday it was 30F outside and MAF was reading 3.6 to 4 grams/sec Today it was 12F outside and MAF was reading 2.6 to 2.9 and idling smooth as butter when I let it sit when I got to work. During the trip it almost stalled out twice and each time MAF spiked to nearly 5 while the car was partially warmed up Diagnosis confirmed: Faulty MAF.. either it is not heating right or it is broken when cold and once the car warms up the sensor starts working right.... and the Subaru Dealer Tech could not find this? it literally stares you in the face.... Link to comment Share on other sites More sharing options...
dgoodhue Posted February 24, 2018 Share Posted February 24, 2018 It is a little premature to confirm this is your issue until you replace the part and resolves your problem. I would not say the difference between 3 and 4 grams per sec is staring the technician in the face. I almost never look at the g/sec for diagnosis of drivability. If the main O2 sensor feedback is working properly, it should eventually compensate for the change once the ECM is in closed loop operation. What does the vacuum read at both of those temperature (values)? What does the AFR look like? Link to comment Share on other sites More sharing options...
dgoodhue Posted February 24, 2018 Share Posted February 24, 2018 FYI I am not trying to be argumentation, just playing devils advocate. I have done a bunch diagnosis on one particular vehicle using my scan tool for local owners. If your MAF was faulty I would expect erratic changing values or larger difference and the fuel trims to be out of range. Link to comment Share on other sites More sharing options...
YeuEmMaiMai Posted February 24, 2018 Author Share Posted February 24, 2018 It is when the car cannot idle right and wants to stall when coming to a gradual stop... why would maf report correctly at 19F and not report correctly at 30F.. that is staring right in at the tech...something is not right here. Air density is directly related to temperature and MAF should not be reporting higher density at a higher temp.. that goes against the laws of physics... Maybe I should be scotty kilmer and use a cigar to smoke my intake tract lol Link to comment Share on other sites More sharing options...
cww516 Posted February 24, 2018 Share Posted February 24, 2018 Well, Wikipedia says that a good check is to whack the sensor with the back of a screwdriver while the car is running and see if anything changes- if you're thinking there might be an intermittent connection in the sensor itself, I'd give that a whirl while logging both mass airflow and intake air temperature, see if you can see anything in the log file. There's also a diagnostic procedure in the vacation pics to test both sides of the MAF sensor (velocity and temperature). I'd rattle that off, but I think the MAF sensor is different on the FB25, although I could be wrong. Also, in the tech's defense- the diagnostic tree in the vacation pics says that at warm idle, car in neutral, everything turned off, anything between 2 and 5 g/s is considered passing, so the difference you're seeing wouldn't necessarily catch their eye. Doesn't mean there's not something there, though. Link to comment Share on other sites More sharing options...
YeuEmMaiMai Posted February 24, 2018 Author Share Posted February 24, 2018 those are integrated into the same sensor assembly right behind the air filter... 2-5 that is a HUGE difference when the engine is idling at 6XX rpm ... btw I did my testing on fully warmed up and cold and when everything is good (in park) the readings are 2.6 to 2.9... when it runs like crap MAF is all over the place and short term goes right to 35% correction... starting up car and smelling rich for a moment is one thing but smelling raw fuel is quite another... Link to comment Share on other sites More sharing options...
cww516 Posted February 24, 2018 Share Posted February 24, 2018 They're in the same housing, but there are two discrete sensors in there- should be 3 wires for power/ground/signal on the hot wire (velocity) and 2 wires for the cold wire (temperature). Granted, if you're replacing the thing, it doesn't make a whole lot of difference which one is bad, I'm more curious than anything. Link to comment Share on other sites More sharing options...
YeuEmMaiMai Posted February 24, 2018 Author Share Posted February 24, 2018 Well find out in about 8 days max... funny thing is as the temps get warmer the car returns to normal. IAT seems to be inline with what I would expect based upon outside temp Link to comment Share on other sites More sharing options...
laz Posted February 25, 2018 Share Posted February 25, 2018 You just need to move to a place without winters. Florida is nice! --- Link to comment Share on other sites More sharing options...
nads Posted February 25, 2018 Share Posted February 25, 2018 It is when the car cannot idle right and wants to stall when coming to a gradual stop... why would maf report correctly at 19F and not report correctly at 30F.. that is staring right in at the tech...something is not right here. Air density is directly related to temperature and MAF should not be reporting higher density at a higher temp.. that goes against the laws of physics... Maybe I should be scotty kilmer and use a cigar to smoke my intake tract lol It maybe MAF. Typically issues I have had arise when things get warm, that's when things expand. How do the MAF counts look when driving? Like steady state cruize or going up a hill? Is MAF even in the equation at idle? Link to comment Share on other sites More sharing options...
YeuEmMaiMai Posted February 25, 2018 Author Share Posted February 25, 2018 they are all over the place when the car is drinking gas... relatively normal at other time Link to comment Share on other sites More sharing options...
nads Posted February 25, 2018 Share Posted February 25, 2018 Can you log the coolant temp sensor readings? Link to comment Share on other sites More sharing options...
YeuEmMaiMai Posted February 25, 2018 Author Share Posted February 25, 2018 ok i will get some logs...i cleaned MAF and changed out air filter Link to comment Share on other sites More sharing options...
dgoodhue Posted February 25, 2018 Share Posted February 25, 2018 Do you have an oiled aftermarket air filter like a k & n? Link to comment Share on other sites More sharing options...
YeuEmMaiMai Posted February 25, 2018 Author Share Posted February 25, 2018 nope 100% stock Link to comment Share on other sites More sharing options...
YeuEmMaiMai Posted February 26, 2018 Author Share Posted February 26, 2018 i tried to upload files but this website will not allow it so you are just going to have to take my word for it. I cleaned MAF and fuel economy went up a bit on my drip from 22.5 to 23.1 Coolant temp came up to and remained stable at 192-194F Link to comment Share on other sites More sharing options...
laz Posted February 26, 2018 Share Posted February 26, 2018 they are all over the place when the car is drinking gas... relatively normal at other time I just calculated my mpg’s at the pump. 22mpg over 16 gallons. --- Link to comment Share on other sites More sharing options...
nads Posted February 26, 2018 Share Posted February 26, 2018 i tried to upload files but this website will not allow it so you are just going to have to take my word for it. I cleaned MAF and fuel economy went up a bit on my drip from 22.5 to 23.1 Coolant temp came up to and remained stable at 192-194F So has your running cold issue gone away? As I recall you had a no to low heat situation and the car never would reach full temp. Link to comment Share on other sites More sharing options...
YeuEmMaiMai Posted February 26, 2018 Author Share Posted February 26, 2018 They found air in the cooling system (again) and bled it out. car is much warmer now the car running rough/hesitation when starting off when cold has not gone away... Link to comment Share on other sites More sharing options...
nads Posted February 26, 2018 Share Posted February 26, 2018 Well you got 1/2 the issues resolved. Link to comment Share on other sites More sharing options...
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