big_dummy Posted January 9, 2012 Share Posted January 9, 2012 Hi, I have a 2001 Forester that has issued P0301, P0302, P0303, P0304 codes (most frequently cyl 3 and 4 together (not in pairs of 1 and 3, 2 and 4)). In my OBD software, I get activity on O2 bank 1 sensor 2 (0-1V), but constant 0V on bank 1 sensor 1. It never moves up no matter the how long the engine runs, nor the amount of throttle applied. I replaced the sensor with a Bosch (since it was the weekend and it was the only thing AZ had) but no change. The low RPM (takeoff and idle) is where the misfire occurs, if I am above 1500 or so, no issues at all. Also replaced the fuel filter, is my next step a fuel pressure test? I have oem parts coming for a valve cover seal job, and will replace plugs, wires, and grommets/boots together, but don't think this is part of the misfire. Any ideas? Thanks guys. Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted January 9, 2012 Share Posted January 9, 2012 so many possibilities. a coupla things to put on your list to check; IACV - might explain poor running at low rpm. alt/battery; my wife's OBW began throwing spurious codes, mostly misfires, when her battery had a bad cell. Link to comment Share on other sites More sharing options...
Cougar Posted January 9, 2012 Share Posted January 9, 2012 I would guess then you may have a severe air leak on bank 1 somewhere after the MAF or the injectors may not be working correctly. Have you looked at the fuel trim values? Link to comment Share on other sites More sharing options...
Fairtax4me Posted January 9, 2012 Share Posted January 9, 2012 Low RPM misfires at idle or under load are typical with bad spark plug wires. If the misfire occurs when the engine is cold (right after first startup) then the O2 sensor is not at fault because the ECU does not take O2 sensor data into account until the sensor warms up to about 1100 degrees. It takes a few minutes. The software may not deciphering the information from the ECU correctly thus it reads no voltage even though it may be working correctly. Link to comment Share on other sites More sharing options...
porcupine73 Posted January 9, 2012 Share Posted January 9, 2012 What brand/type plugs and wires are in there? Link to comment Share on other sites More sharing options...
big_dummy Posted January 10, 2012 Author Share Posted January 10, 2012 Thanks for the ideas. I have a new set of wires and plugs (OEM) that I will be installing in a day or two. Also have been putting off a valve cover seal job for far too long and will do that as well. All of that needs to be addressed anyway, hopefully it will show an improvement. I will keep you guys posted on that. Good thought about the software not deciphering ECM data. Perhaps I will put a DVM on the ECM cable if I can do it without disconnecting the ECM to confirm. Is it possible that all wires failed at the same time? Is it possible that it could be the coil? Can I test it on an ohmmeter? Has anyone used BWD/Intermotor? Normally I would use OEM, but local store is quick and convenient. I think my software monitors fuel trim, but I don't know how to diagnose problems based on the information. What do I need to know? More info - Misfires don't occur until the engine warms up (5+minutes) but that may be because it is cold here and the idle is higher when the temperature is cold, lower when the engine warms up. The problem first showed up on the coldest morning of the year so far. Here is my list of steps based on recommendations so far: 1. Replace wires and Plugs to OEM (preventive/needs to be done anyway) 2. Check Fuel trim in software to determine if the car is adjusting fuel delivery based on O2 sensor information. If so, O2 readings in software are wrong, sensor is likely good. 3. Idle Air Control Valve - how do I test this? 4. Battery/alternator testing Would it be worthwhile to do a fuel pressure test? Would a lack of fuel cause misfires? Link to comment Share on other sites More sharing options...
Cougar Posted January 10, 2012 Share Posted January 10, 2012 You stated you replaced the O2 sensor with a new one so the sensor should be ok. The fact that you aren't seeing any voltage from it is puzzlling. If there was a problem with the wiring to the sensor you should see a code indicating that. Have you checked to see if the injectors are working ok on the right side for #1 and #3 and they are firing ok? Link to comment Share on other sites More sharing options...
big_dummy Posted January 10, 2012 Author Share Posted January 10, 2012 Good point about the wiring of the sensor. It would have an error code if the ECM was truly not wired. I know you are right because when I disconnected the cable, I got an error code. How do I check the injectors? The only way I know is a big screwdriver used as a stethoscope. Is there something more technical? Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted January 10, 2012 Share Posted January 10, 2012 3. Idle Air Control Valve - how do I test this? AFAIK, most folks use throttle body cleaner to clean it. (be careful what solvent you use) I have no idea if there's a 'test' for it. Link to comment Share on other sites More sharing options...
Cougar Posted January 10, 2012 Share Posted January 10, 2012 How do I check the injectors? The only way I know is a big screwdriver used as a stethoscope. Is there something more technical? Try removing the electrical connection to #1 injector and see if there is a difference in the engine operation. Link to comment Share on other sites More sharing options...
big_dummy Posted January 21, 2012 Author Share Posted January 21, 2012 UPDATE: It seems to be resolved!!! Thanks for all your help guys. Here is what I did... Replaced O2 sensor - no change, still misfiring on all cylinders. Removed air filter - no change, installed new unit - no change. Replaced fuel filter - no change I had so much oil in the spark plug cavities that I figured it might have been ignition related. Since it needed it really badly anyway, I replaced valve cover seals, spark plug seals, and rubber washers on valve cover bolts, spark plugs and spark plug wires (all OEM of course) - vastly significant improvement for 5-10 miles, then misfiring again. Since I had the valve covers off, went ahead and readjusted intake and exhaust valves using feeler gauge set. They weren't far off, but it is very easy to do anyway. Ordered coil (OEM of course) and replaced coil - 100% improvement Still getting a problem with the 0V on bank 1 sensor 1 O2 sensor, but no performance problems. I think I will go ahead and order an OEM O2 sensor to replace the BSCH that I got from the local store. I much prefer OEM stuff. The local stores are good for weekend work and diagnostics, but if you want to keep the car running, OEM is the only way to fly! Thanks for all the help. :headbang:You guys ROCK!!!! Keep up the great work! Link to comment Share on other sites More sharing options...
Cougar Posted January 22, 2012 Share Posted January 22, 2012 use a DVM meter to check the voltage of the O2 sensor at the input of the ECU. Compare that reading with the other front sensor and see if they are about the same. If they are then the trouble would have to be inside the ECU. Link to comment Share on other sites More sharing options...
big_dummy Posted April 15, 2012 Author Share Posted April 15, 2012 Thanks for all the help, I have gotten the misfires handled by replacing coil pack, valve cover gaskets, wires, plugs, and I have even adjusted the intake and exhaust valves using feeler gauges since I had the valve covers off. I have only one code (P0420) left which is vexing me, and I am still getting nothing but 0V on the front O2 sensor in my software. I would like to check the voltage directly on the sensor, but I don't know the pinout. I have the service manual, but it doesn't indicate the signal type for individual pins (which are heater, which are sensor). There are five wires coming from the sensor, does anyone know what the wiring is supposed to be for the 2001 Forester front O2 sensor? Any help would be greatly appreciated. Link to comment Share on other sites More sharing options...
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