May 30, 200718 yr I Have A Customer With A 2002 Legacy Outback With 78k, The Check Engine Light Comes On With Codes For Number 3 & 4 Cylinders, The Car Also Stumbles And Wants To Stall Once And A While Coming To A Stop And At Times Will Stall. The Car Runs Great All The Time But Only Gives The Problem When Either Slowing To Stop Or At A Complete Stop, I Have Changed The Coil Pack, Plugs & Wires, Last Week I Tried To Change Both Air Flow Sensors (o2 Sensors) The Car Now Runs Much Better With More Power But Still Will Stumble Or Stall While Coming To A Stop...any One Ever See This Before, Any Help Would Be Greately Appreciated.
May 30, 200718 yr 1) Which codes? Misfire (P0303, P0304)? Any others? 2) Idle RPM? 3) Idle quality (smooth, lopey, misfiring, etc.)? 4) Did you use new OEM coil/plugs/O2s? 5) How's the electrical system doing (voltage at battery terminals at idle)? 6) If DTCs are for misfire, the problem may be other than ignition-related. 7) Please restrict the use of capital letters, I'm getting a headache. 8) Welcome to the forum.
May 30, 200718 yr spark plugs should be stock NGK's. and the spark plug wires should be Subaru only, do not attempt to use other wires on this engine. not all subaru engines are like this, but in this case Subaru wires should be used. bgd, is that you?
May 30, 200718 yr How's the fuel pressures and fuel pressure regulator and fuel filter? Also, while idling with the air filter out of the way, a shot of throttle body cleaner aimed up at the IACV intake just before and above the throttle butterfly, might be a quick easy thing to try... I think there was something on EndWrench that said to make sure the negative battery cable was clean and securely connected in cases of poor idle.
May 30, 200718 yr when it stalls does it sputer or just quit? Missfire can be fuel supply as well as ignition. nipper
May 30, 200718 yr Author spark plugs should be stock NGK's. and the spark plug wires should be Subaru only, do not attempt to use other wires on this engine. not all subaru engines are like this, but in this case Subaru wires should be used. bgd, is that you? Yes all parts I use are OEM from a Subaru dealer, I have been working on Subarus for 27 years and never been stumpted before,thanks for the thoughts
May 30, 200718 yr Author How's the fuel pressures and fuel pressure regulator and fuel filter? Also, while idling with the air filter out of the way, a shot of throttle body cleaner aimed up at the IACV intake just before and above the throttle butterfly, might be a quick easy thing to try... I think there was something on EndWrench that said to make sure the negative battery cable was clean and securely connected in cases of poor idle. Fuel pressure at idle was around 40 Lbs. and steady. Fuel filter is new and I removed the back of the air filter cover and gave a shot of Carb cleaner but no help still have same problem
May 30, 200718 yr Fuel pressure at idle was around 40 Lbs. and steady. Fuel filter is new and I removed the back of the air filter cover and gave a shot of Carb cleaner but no help still have same problem Since i will have some trust in your years of exp, do you have an ECU you can try? Also ( i am so glad i keep old test equipment) do you have an oscilliscope? nipper
May 30, 200718 yr Author 1) Which codes? Misfire (P0303, P0304)? Any others? 2) Idle RPM? 3) Idle quality (smooth, lopey, misfiring, etc.)? 4) Did you use new OEM coil/plugs/O2s? 5) How's the electrical system doing (voltage at battery terminals at idle)? 6) If DTCs are for misfire, the problem may be other than ignition-related. 7) Please restrict the use of capital letters, I'm getting a headache. 8) Welcome to the forum. Sorry about the caps Only codes are PO 303 & 304 Idle RPm is 700 and smooth unless it decides to stumble and then idle real rough kinda like a huge vacum leak All parts I use are OEM from Subaru Voltage at idle and on acceleration is 13.7 volts Thanks for the reply
May 31, 200718 yr Not sure if this helps, but I saw this on EndWrench: A rough engine idle condition may occur when the vehicle’s battery is disconnected for less than 30 minutes on some 2001 and later Subaru vehicles, up to and including the 2003 Legacy and Baja. The rough idle condition only affects four cylinder, non-turbo vehicles. 2004 model year vehicles may also be affected. Clearing the memory with the Select Monitor will correct this condition. Also, the ECU will most likely clear itself if the battery is allowed to remain disconnected for more than 30 minutes.
May 31, 200718 yr Author how is the IAC functioning? Can you make the car do this on demand? nipper No it will only act up when it wants to, Usually every day it will act up at least once
May 31, 200718 yr Author Since i will have some trust in your years of exp, do you have an ECU you can try? Also ( i am so glad i keep old test equipment) do you have an oscilliscope? nipper I wish I could find a brain to plug in and try I have heard about newer Subarus with brain problems and heard about trying to reprogram (flash) the brain...Still waiting to hear from a reply on that one.
May 31, 200718 yr hrmmmm This sounds like an intermittent electrical issue. Do you have a scanner that can freeze data in real time? What i would try is dissconnets and re connect the conectors for the injectors, temp sensor, cam and crank sensors. This will clean the terminals. i am suspicous of the cam or crank sensors. Usually this is a sympton of one of them going bad. Make sure they are clean at the business end. INspect the knock sensor. The knock sesnor wil normally throw a code. The Cam and crank sensors wont if its an odd ball intermittent issue. nipper
May 31, 200718 yr Author I Have A Customer With A 2002 Legacy Outback With 78k, The Check Engine Light Comes On With Codes For Number 3 & 4 Cylinders, The Car Also Stumbles And Wants To Stall Once And A While Coming To A Stop And At Times Will Stall. The Car Runs Great All The Time But Only Gives The Problem When Either Slowing To Stop Or At A Complete Stop, I Have Changed The Coil Pack, Plugs & Wires, Last Week I Tried To Change Both Air Flow Sensors (o2 Sensors) The Car Now Runs Much Better With More Power But Still Will Stumble Or Stall While Coming To A Stop...any One Ever See This Before, Any Help Would Be Greately Appreciated. Problem solved I sent the customer to a local Subaru dealer and they re flashed the computer, (updated it) And so far so good.......I think I'm off the hook on this one
June 4, 200718 yr Doorstop, when you say you "tried to change the 02 sensor," does that mean you tried but couldn't change it? Or you tried and did change it? Just wondering cuz my prob turned out to be the front 02 sensor: Here is my review from a diff thread: I have a 2001 Forester L with 85k miles on it. I have been chasing an intermittent hesitation under load problem for the past year, since about 80k miles. Only occurred when engine was warm. The front 02 sensor had been replaced once at 40k miles. I suspected it again this time, but since the only codes thrown had been cyl's 2&4 misfire ( p0302 & p0304) I assumed it must be ignition related. So I replaced plugs and wires 8 months ago...no effect. Did the dollar bill test over exhaust pipe, it was fine. Misted the coil, no sparks. I mentally sort of ruled out the fuel filter since it only happened when the engine was warm. Finally, a week ago while cruising on hwy at 65 mph, I felt the hesitation again (I wasn't even accelerating this time) and a new code was thrown....p0172. AutoZone read it for me, I described the symptoms to the guy and asked if he thought it might be the front 02 sensor. He said, "absolutely." So I decided to replace it next. Cost me $100.75 incl tax for the oem part# 22791aa00a from Cityside Subaru. I asked the Parts guy there if his experience was that this model engine needed a new front 02 sensor every 40k miles. He said, "no, these sensors are good for 100k miles." Well, bullsnot on that. I replaced the new front 02 sensor in 1 hour reaching from the top over the passenger side of the engine using an adjustable wrench. Be sure to use the thread lube so you can get it out easily next time.....after another 40k miles. I took out the air channel assembly first for better access. That seems to be the fix. No further hesitation since. Car runs like new.
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