grinderdust Posted January 17, 2015 Share Posted January 17, 2015 Sorry if this has been covered, I searched but couldn't find the exact problem. This is a 98 legacy outback wagon with all the goodies and a 5 speed manual. Car has been giving me poor mileage and performance issues for a while now. I just replaced the knock sensor with a cheapie from ebay. It seems to run better and the CEL hasn't come back yet. I am still noticing a very low idle but at least it is not stalling anymore when I push in the clutch. I notice that if I just barely touch the throttle that the rpms drop for a split second before it starts to tach up. This causes some hesitation and makes the car buck sometimes if I have to slow down and pick up again without shifting. Anyway, here are some questions: Is the throttle position sensor adjustable? I ask because it seems that the intake butterfly might be opening a crack before the throttle sensor picks up it's position. This would cause a temporary lean condition leading to the symptoms I describe. Does anyone know what else might cause this? Do EFI cars even still have accelerator pumps? How can I adjust the idle up a bit? I don't have a way to verify the rpms but the tach on the dash says it is idling below 500 and sometimes even lower. The idle is so low that it knocks sometimes if I have to get moving quickly or start off on a hill. I live in an area with extremely steep hills so this car is a bit of a challenge to drive. Thanks for looking and thanks in advance for any help I can get. Quote Link to comment Share on other sites More sharing options...
lmdew Posted January 17, 2015 Share Posted January 17, 2015 The TPS is adjustable but I doubt that is your problem. Start with he simple stuff: - Copper core plugs NGK, how old are your plugs? - Clean the IAC, it controls the idle speed - New NGK or Subaru Plug wires - New Air Filter, & clean the MAF - New fuel Filter Do as necessary to bring your maintenance up to date. No accelerator pump. 1 Quote Link to comment Share on other sites More sharing options...
grinderdust Posted January 17, 2015 Author Share Posted January 17, 2015 Wow, fast reply, thanks. Plugs,wires,coil all replaced within the last 1000 miles. Made it run ever so slightly better. Replacing the knock sensor and clearing all the codes made a much bigger difference. I will look up IAC (intake air control?) and MAF (mass airflow?) and how to to clean them. Air filter is not new, not old but I vacummed it out and I can still see light through it. Maybe I'll go ahead and change it to be sure. Would a fuel filter do this? I thought the fuel sytem on an EFI car was put under considerable pressure after the filter. Also, the car runs fantastic once it is moving through the gears. The maintenance is not exactly up to date but I can't get too spendy on this. Car is at 180,000 and it's kind of rusty, ripped axle boot or 2 etc. etc. Quote Link to comment Share on other sites More sharing options...
lmdew Posted January 17, 2015 Share Posted January 17, 2015 MAF Sensor, they have MAF cleaner spray at Auto Parts Stores IAC - Grab a can of Seafoam and pour 1/3 of the can into the large 1" tube going to the Idle Air Control IAC Valve. Let it sit for about 30 minutes and then start it up. Expect smoke as the seafoam will be sucked into the cylinders. Quote Link to comment Share on other sites More sharing options...
grinderdust Posted January 26, 2015 Author Share Posted January 26, 2015 Returning for an update...a whole new can of worms has opened up. Seems at least some of the worms are escaping the can through the head gasket!!!! Did the MAF cleaner and the seafoam into the IACV. Drove up to the local ski resort and the car overheated bad. The main reason I am posting at this point is to keep people from spending unneccesary money. My advice is to look at the coolant reservoir before spending a dime on a 2.5. If it smells like exhaust or has a film, the head gasket is failing. If the car is rusty or high miles,it's not worth putting any money into it. I just spent close to $200 and wasted a bunch of time on coil,plugs,wires,knock sensor,seafoam,etc....Even though this engine is a basket case and on it's way out, I had the codes read again yesterday. I now have a vehicle speed sensor code. After some reading, I found out the IACV trouble code is likely being caused by a failing Vehicle speed sensor which causes the the computer to go into limp mode which causes a poor idle which causes the IACV code and also the knock which causes the knock sensor code. All this is a separate issue from the low coolant/ headgasket problem. So.... please check the VSS and the headgasket before you spend money on tune up parts. Also, I do not recommend pouring seafoam into the IACV or anywhere for that matter. Here is why: I poured less than 1/3 can into the air tube leading to the IACV and let it sit for 30 minutes. I then started the engine, which started rough but smoothed out quickly. I knew full well that even a small amount of liquid in the combustion chamber could cause a temporary hydrolock (this is why I only used about 1 1/2 oz.) On most engines this wouldn't be a problem, but if the head gasket is near failure (All the phase one 2.5's are) the increased pressure could blow it out big time. Not saying this caused the gasket to blow but it is definitely not helpful in this situation. Thanks for reading the long post and I hope It saves somebody some trouble. Quote Link to comment Share on other sites More sharing options...
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