ferret

I have seen this a few times where it was the Front Oxygen sensor. Happens after warmup. Sometimes so bad the engine cuts out completely, only to restart without a hitch. When it's acting up, stop the car and UNPLUG the front oxygen sensor. This WILL set a code and the Check engine light. The engine is now running in OPEN loop on a preset of fuel mixture. Now drive the car. If the cutout is gone, the front sensor is a good candidate. If not, my next candidate is the MAF. A good cleaning here is inexpensive using an aerosol MAF cleaner from an auto parts store. On some vehicles, you can unplug the MAF, cycle the key a few times and the engine will start and run again in open loop mode, although not very well. Just a few thoughts after reading this thread.

I don't think the front O2 sensor was defective, I would put the original back in then go after the Lean P0170. The 99 was a MAF engine and each time I troubleshot a P0170 it turned out to be a vacuum leak. So I would check hoses and their seating. It could also be the MAF needs cleaning also, so a can of CRC MAF cleaner is a cheap fix to try. I DID have 2 that along with P0170, the cruise didn't work. The vacuum hose, at the cruise actuator, was off. That's mounted on the passenger side firewall, and when that little hose comes off, many times you will not even notice it unless you are looking for it. Good luck.

I use my years and a vacuum gauge to troubleshoot this code. With the engine warm and running, from under the hood, hit the gas for a few seconds and LISTEN, you should hear a 'click' from the EGR solenoid mounted right below the back pressure transducer. Then see the EGR diaphragm move. No click, then I would put the vacuum gauge right there, ensure you have Ported vacuum coming to the solenoid, and AFTER when you hit the gas. From there it goes into the Back pressure transducer. If it is present coming in, but not out DOES NOT mean the transducer is bad, it could be a clogged line from the exhaust to the bottom, OR full engine vacuum missing from the 4th port on it. If there IS ported vacuum coming thru the transducer when you hit the gas, then the EGR itself it the suspect. It could have a damaged diaphragm or just STUCK. In this case I take it off and clean the pintle on the tip. Only saw 1 stuck in all the years I have worked on these. A few defective EGR's, and many clogged tubes and defective solenoids.

Airbag light is not manually reset. Evert time the car starts, it runs diagnostics and if it finds any fault, the light remains on. You need someone to read the code for you to be certain what the problem is. See the age of the car AND if it were NOT in an accident, I might ask if the horn or cruise ( if equipped ) work. Right around the 10-11 year mark, I see Clockspring/Rolled Coil failures. This is the flat wire coil assy that allows power to the steering wheel controls ( horn, cruise AND air bag module ) while allowing the steering wheel to be turned more than 360 degrees.

They are expensive. Even the part itself on EBAY. I usually look on Ebay for an entire Throttle Body with the IACV on it. You can usually get one cheaper than the individual part. http://www.ebay.com/itm/1999-1998-97-98-99-subaru-forester-impreza-2-5-throttle-body-/260900398761?pt=Motors_Car_Truck_Parts_Accessories&hash=item3cbee026a9&vxp=mtr http://www.ebay.com/itm/00-01-SUBARU-LEGACY-OUTBACK-2-5L-4CYL-THROTTLE-BODY-THROTTLE-VALVE-ASSY-/120895629051?pt=Motors_Car_Truck_Parts_Accessories&fits=Make%3ASubaru&hash=item1c25f0e6fb&vxp=mtr Let me ask ...... is this a 5 speed ? If it is, the Idle Switch on the transmission can be causing this also. I usually see this when someone is driving/moving. It tells the ECU when you are in gear, This and speedometer pulses tell the ECU you are moving, so the ECU does NOT control the idle. When the switch goes BAD, the ECU sees the car moving, but NOT IN GEAR, like coasting in neutral. So the ECU TRIES to control the idle, but since you ARE in gear, it can not, so it sets P1507.

Sticky thermostat, WRONG ( aftermarket too shallow ) thermostat, radiator fans maybe not plugged, radiator partially blocked ( feel the entire radiator by hand after warmup ). Just a few things to look for before going for headgaskets. But even if they were replace, I have seen a few cars come in that either used aftermarket ( Ebay I suspect ) gaskets and fail again, OR surfaces not cleaned / heads not planed and then they wonder why it failed again. Just what first comes to mind reading this thread.

not rich, but just plain bad ..... does your 01 have an EGR?

When it idles rough, does the exhaust smell REALLY BAD ?

Is this a problem at idle or at speed?

After re-reading the first post, do you have loss of power while driving? If so my post above still stands. Or do you have an Idle problem after running, but the car runs fine at highway speeds? Different problem.

You are in the year range for some front O2 sensors that act up. I have seen MANY of these since 2002 even to the point an Outback wouldn't even start and was flatbedded to the dealer only to start there. Does it do it AFTER warmup? If so this is the start of the front o2 symptoms diagnoses. If you can, when it's acting up, shut off the engine. Open the hood and on the passenger rear side by the firewall, reach down and unplug the front o2 sensor ( THIS WILL SET A CHECK ENGINE CODE ). Now start the vehicle and drive it to see of the bucking had stopped. ( It WILL run, you are in open loop mode and running on a set of predetermined fuel mixture parameters ). If the bucking STOPS, chances are you have a defective front sensor. If it continues, the front sensor is NOT the problem. Either way you now have to reset the Check engine light, but have done at least 1 valid check for your problem. This certain run of sensors ( 2001 to 2004 various models ), after warmup intermittently indicate the exhaust is RICH. In turn the ECU leans out or shuts down the fuel injectors until the sensor reads nothing. I mapped one years ago while trying to diagnose my first one of these. Then you have to determine, " is this the Cause, or the Effect of something else".

Check the small coolant hoses on the IACV and Throttle Body. When you removed and replaced the intake, it's easy to damage these so there is just a small pinhole that weeps and coolant runs down the side of the motor by the oil pan. Depending on where it runs down, it also may follow the head and look like a leaking head gasket. A guy once told he had a leaky head gasket and was relieved to find out it was just a small coolant hose buried under the intake.

With the engine warm, open the hood and raise the RPM. You should hear a click from the EGR solenoid just below the EGR valve, then see the EGR diaphragm move. If you do not hear the click, then chances are the solenoid is defective. If you DO hear the click, but the diaphragm does NOT move, then use a vacuum gauge to follow the hoses back through the BPT ( back pressure transducer ) to the ported outlet on the intake manifold. IF you hear the click AND have vacuum at the EGR, then it is either stuck ( remove and clean the pintle at the bottom ) or the diaphragm is leaking. Either way replacing it should fix it. MOST TIMES, I have found either a clogged port, or the solenoid inlet/outlet is clogged.

Here is some interesting reading ... about reply #31, I posted a fix that I have now 'tripped' over a few more times on others cars I fix. http://www.subaruforester.org/vbulletin/f88/low-idle-stuttering-erratic-jerking-various-rpms-76450/

I AGREE .... used head .... I did this 2 years ago when my timing belt shreaded. choices $900 to rebuild my heads, or $200 for both from a 2003 legacy with 85K. http://www.subaruforester.org/vbulletin/f88/every-2-5l-interference-engine-64410/ Took the used ones ...... only down side, I never used oil before between changes, now I use a quart .... not a lot, but something that didn't cross my mind at the time. Would I do it again ....ABSOLUTELY .... can't even predict if the rebuilt heads wouldn't develop an oil seal problem either.

They have been around a LONG time. I have dealt with them since the mid 80's over the phone and driving from NJ to pick up. Did a LOT of Air suspension changes in the 90's on Legacy's and got the replacement strut/spring assy's from them. Again before the internet. In the past 10 yrs or so, since the internet, their prices have definitely gone up. You can still haggle a little bit with them, but if you have a Subaru, chances are they have a used part for it. And if you need a manual tranny from them, they defiantly have the 'snout' kit with the stainless steel sleeve and bearing to fit. They will recommend that even for tranny's they sell.

Check this link .... page 2, post 11 is what I usually find: http://www.ultimatesubaru.org/forum/showthread.php?t=102171&page=2

Starting in 2002, Subaru moved the valve to the rear crankcase end. Different part number and threads. Up to 2001, it's in the throttle body with the valve opening toward the threaded end ( toward the throttle body ). From 2002 on, it's in the rear crankcase, just above the rear separator plate ( the other end of the hose ), different thread size, and now the valve opens to the hose end ( still toward the throttle body ). Peaty ( those who know he documents the world from other Subaru Boards ) documented it at the link below. If you can't see the pictures, you have to register, but registration is free: http://www.scoobymods.com/pcv-valve-t16.html?t=16&highlight=pcv

I had a similar problem with MY04 Forester. Many others I have talked to since, and posted on many Subaru boards have now come to the same conclusion. You can read about it: http://www.subaruforester.org/vbulletin/f88/low-idle-stuttering-erratic-jerking-various-rpms-76450/index3.html#post887065

Right out of the EJ engine Technicians Reference Manual: The 2.2 liter (SOHC) (Phase 1) has been enhanced starting with 1997 model year. The single overhead camshaft engines have had internal and external changes that yield an approximately 10 % increase in power and 3% increase in fuel economy. Accomplishing this involves many factors, one of which is engine friction reduction. The piston, a major source of engine friction has been coated with a friction reducing agent called Molybendum. This thin coating not only allows a smoother travel through the cylinder but also reduces cylinder wall scuffing. This coating will wear off over time and is not an indication of a problem. The skirt of the piston has been reshaped and the overall weight has reduced by approximately 100 grams. Compression ratio has been increased to 9.7 to 1 by reshaping the crown of the piston. This eliminates the clearance that was available between the piston at TDC and a fully opened valve. Piston pin offset has been changed to 0.5 mm. Piston to cylinder wall clearance has been reduced by increasing the piston diameter. Another source of high engine friction is the valve train. Hydraulic lash adjusters are always in contact with the camshaft or valve rockers. The hydraulic pressure of the lash adjuster must be overcome during operation and the most critical time of engine start. To overcome this situation and to contribute to the total reduction of friction loss the SOHC engines will have solid valve adjusters. The scheduled service of these valve trains is set at 100,000 miles and is not required during the PDI. The SOHC engine uses an adjustment screw and locknut. The intake manifold has been reshaped to increase the air flow mass and speed, contributing to improved low and mid engine speed operation. Components located on the intake manifold have been relocated as compared to the 1996 models. EGR Solenoid, Purge Control Solenoid, etc...

I had a similar problem last summer on MY04 Forester. If your Outback has an EGR, and I'm pretty certain it does, you can read what I documented over on Subaruforester.org: http://www.subaruforester.org/vbulletin/f88/low-idle-stuttering-erratic-jerking-various-rpms-76450/index3.html#post887065

I would contact CCR, sounds like the heads were NOT torqued properly. The pressurized oil passage to the heads is toward the front top on the drivers side ( IIRC ) and toward the top rear on the passenger side. Both sides use the same gasket,, so it's toward the front on the top of one side and the rear on the other. But this is without seeing, touching or being around the vehicle, just from your description. Take pictures and send them to CCR. They used to give a 3yr/36K warrenty and this is something you could not have caused.

If you have the Auto-Climate controls, here's a writeup for the 03/04 Forester: http://www.subaruforester.org/vbulletin/f85/diy-hvac-bulb-replacement-2004-forester-51964/

If you own a M/T, this can also be the sign of a defective neutral switch. Car coasting while in gear, very normal, but the neutral switch indicates to the ECU you are in neutral not a gear, so the ECU tries to control the idle speed and is unable to. Later models set a P1507 IIRC. If you have an automatic, follow the recommendations in the service manual for P0507. The above does not apply.