Mike_N_Austin Posted April 17, 2006 Share Posted April 17, 2006 My State Inspection is up and they will not give me a stick if the check engine light is on......or if the computer reads a recent hard code fault. I took to Autozone and got the following - Misfire on 3 - Misfire on 4 - Faulty Knock Sensor - Faulty forward O2 sensor (the one located closest to the engine I have a 2001 Subaru Forester with 191K miles. I pulled the engine and resurfaced the heads last year at approx 175K miles. The misfire codes have existed since that time.....the Knock and O2 sensor codes are fairly new. Please help !!! :-) Link to comment Share on other sites More sharing options...
nipper Posted April 17, 2006 Share Posted April 17, 2006 with that milage the 02 sensor makes sense. Misfire can be loose connections on the fuel injectors. Also its interesting since it is a pair are on the same ignition coil. Both cylinders fire at the same times, its known as a waist spark system. Out of curiosity, when you did the HG, did you fully remove the spark plug wires? How old are the spark plug wires? Check the wirining and make sure you did not accidently upset a connection. Inspect the knock sensor and look for cracks. nipper Link to comment Share on other sites More sharing options...
Mike_N_Austin Posted April 17, 2006 Author Share Posted April 17, 2006 with that milage the 02 sensor makes sense. Misfire can be loose connections on the fuel injectors. Also its interesting since it is a pair are on the same ignition coil. Both cylinders fire at the same times, its known as a waist spark system. Out of curiosity, when you did the HG, did you fully remove the spark plug wires? How old are the spark plug wires?Check the wirining and make sure you did not accidently upset a connection. Inspect the knock sensor and look for cracks. nipper Thanks Nipper I experienced a very rough idle shortly after I did the HG. It ended up being broken spark plug wire. I ended up replacing the wires with a new OEM set. I also put in a fresh set of NGK plugs. I read somewhere that the plugs have a "crush washer". Perhaps i did not install my new plugs plugs tight enough ? I also remember replacing the front O2 sensor...but my memory could be mistaken on that....(unfortunately I do not keep good records :-) ) I will definitely inspect the knock sensor. Question - is the knock sensor a sensor that can become clogged.....in otherwords, would cleaning it possibly fix the problem with that sensor ? Link to comment Share on other sites More sharing options...
nipper Posted April 17, 2006 Share Posted April 17, 2006 Sparkplugs do have crush washers, and should be checked if you dont think you put them in tight enough. Inspect the coil towers for cracks and clean them of dirt. In the early evening spray the coil with water (use a spray bottle) and look for sparks. A bad knock sensor may cause the codes your seing (fault codes are like 6 degrees of seperation). a faulty knock sensor can be sending the wrong signal, retarding the ignition so much that it is read as a misfire, and the o2 sensor picking up bad emissions, so the o2 sensor thinks its out of range (just a theory people). A knock sensor is a piezo-quartz sensor. It produces an AC signal and the ECU interpits that signal, and changes the spark timing as it seems fit. Aparently there is no min/max setting in the ECU code, so sometimes it can make the car run really odd if it is going bad. All you can do is look at the sensor, see if it is cracked, and check to see if it shorted to ground. It is inexpensive enough to replace just-because. nipper Link to comment Share on other sites More sharing options...
nipper Posted April 17, 2006 Share Posted April 17, 2006 There are also some coil tests you can do, but i dont know if the values from a 98 will carry over to 2001... nipper Link to comment Share on other sites More sharing options...
Mike_N_Austin Posted April 17, 2006 Author Share Posted April 17, 2006 Sparkplugs do have crush washers, and should be checked if you dont think you put them in tight enough.Inspect the coil towers for cracks and clean them of dirt. In the early evening spray the coil with water (use a spray bottle) and look for sparks. A bad knock sensor may cause the codes your seing (fault codes are like 6 degrees of seperation). a faulty knock sensor can be sending the wrong signal, retarding the ignition so much that it is read as a misfire, and the o2 sensor picking up bad emissions, so the o2 sensor thinks its out of range (just a theory people). A knock sensor is a piezo-quartz sensor. It produces an AC signal and the ECU interpits that signal, and changes the spark timing as it seems fit. Aparently there is no min/max setting in the ECU code, so sometimes it can make the car run really odd if it is going bad. All you can do is look at the sensor, see if it is cracked, and check to see if it shorted to ground. It is inexpensive enough to replace just-because. nipper Nipper...Again....THANKS !!!!!!! Looks like I need to start with the Knock sensor then. Can you tell me where it is located and what it looks like ? I understand that is is located somewhere close to the throttle body...but I cannot locate it. Do I need to remove the air cleaner box to see it or to get to it ? On the Knock sensor...dealer is quoting $ 103.79. Best quote aftermarket is $ 80, so far...but nobody has stock. Link to comment Share on other sites More sharing options...
Mike_N_Austin Posted April 17, 2006 Author Share Posted April 17, 2006 Would it be worth it to spend the $ 60.00 to have diagnostics run at a dealership ? Link to comment Share on other sites More sharing options...
nipper Posted April 17, 2006 Share Posted April 17, 2006 if it was me, i would try the knock sensor first. All the dealer will do is pull the codes and tell you what you already know. You should be bale to get cheaper prices, around 60.00 if you go to one of the suppliers recomended here...www.SubaruGenuineParts.com toll free: 800.962.0822 mention this site and see if they can do you better Link to comment Share on other sites More sharing options...
Mike_N_Austin Posted April 17, 2006 Author Share Posted April 17, 2006 They have listed for $ 69...will mention this site...and hopefully the shipping is not too high :cool: do you know where the knock sensor is located ? Link to comment Share on other sites More sharing options...
nipper Posted April 17, 2006 Share Posted April 17, 2006 my book says under the intake manifold runner on the left rear of the engine. Do a search here on knock sensor and you may find a better desription or picture. You dont have to remove the manifold to repalce it, i think its fairly easy. nipper Link to comment Share on other sites More sharing options...
Mike_N_Austin Posted April 17, 2006 Author Share Posted April 17, 2006 my book says under the intake manifold runner on the left rear of the engine. Do a search here on knock sensor and you may find a better desription or picture. You dont have to remove the manifold to repalce it, i think its fairly easy. nipper YEP ! I just located a post on in the archive that has photo's and everything. This site makes these jobs very easy !!! Thanks for the feedback. I am hoping that the knock sensor clears my issues Link to comment Share on other sites More sharing options...
Mike_N_Austin Posted April 17, 2006 Author Share Posted April 17, 2006 Ok Nipper...a few more questions please First...have you really every used a nerf bat on someone ? Second.....can I clear/reset the ECM by disconnecting the battery overnight ? Link to comment Share on other sites More sharing options...
nipper Posted April 17, 2006 Share Posted April 17, 2006 Yes (and worse) and yes, thats a hard reset. The computer will take about 3 weeks to learn your driving habits again nipper Link to comment Share on other sites More sharing options...
nipper Posted April 17, 2006 Share Posted April 17, 2006 opps posted twice.. ignore this .. the nerf bat got away from me nipper Link to comment Share on other sites More sharing options...
cookie Posted April 18, 2006 Share Posted April 18, 2006 That's where it is on my 2.5. Link to comment Share on other sites More sharing options...
Mike_N_Austin Posted April 18, 2006 Author Share Posted April 18, 2006 Well...I pulled the knock sensor last night and inspected it. There are no cracks in the metal end of the sensor. I cleaned the sensor with throttle body cleaner and I also cleaned the contact point on the block. I then re-installed the sensor. I unhooked the ground battery connection and let it sit overnight. When I started it up this morning..the darn codes were still there....they never cleared. I also removed my idle control sensor and cleaned it with throttle body cleaner. I have been having a rough loping idle when in neutral. After cleaning it...and adjusting it....I now have a smooth steatdy idle. I will post this under a new thread for future searches. On the state inspection...I am going to try and get a sticker in a different county. My county is only 1 of a handful in Texas that is holding to the new emission standards Link to comment Share on other sites More sharing options...
cookie Posted April 18, 2006 Share Posted April 18, 2006 Cleaning the knock sensor is not likely to help. They fail internally. Link to comment Share on other sites More sharing options...
nipper Posted April 18, 2006 Share Posted April 18, 2006 Well...I pulled the knock sensor last night and inspected it. There are no cracks in the metal end of the sensor. I cleaned the sensor with throttle body cleaner and I also cleaned the contact point on the block. I then re-installed the sensor. I unhooked the ground battery connection and let it sit overnight. When I started it up this morning..the darn codes were still there....they never cleared. I also removed my idle control sensor and cleaned it with throttle body cleaner. I have been having a rough loping idle when in neutral. After cleaning it...and adjusting it....I now have a smooth steatdy idle. I will post this under a new thread for future searches. On the state inspection...I am going to try and get a sticker in a different county. My county is only 1 of a handful in Texas that is holding to the new emission standards im getting the nerf bat back out. There is nothing to clean with the knock sensor, like cookie said it works or it doesnt. The reset wont rid you of codes if the source of the codes is always there. nipper Link to comment Share on other sites More sharing options...
Mike_N_Austin Posted April 18, 2006 Author Share Posted April 18, 2006 im getting the nerf bat back out.There is nothing to clean with the knock sensor, like cookie said it works or it doesnt. The reset wont rid you of codes if the source of the codes is always there. nipper LOL But I was told here and other places to inspect for cracks. There were no cracks. I have also read and heard that just because you get a fault code on a part it does not necessarily mean that that particular part is actually failing. The code could be an effect of another downstream or upstream cause. So I am really leary about throwing money at parts if I don't know for sure that they are faulty. I have done this many times in the past. Link to comment Share on other sites More sharing options...
Mike_N_Austin Posted April 18, 2006 Author Share Posted April 18, 2006 Ok...calling on the part now Link to comment Share on other sites More sharing options...
Mike_N_Austin Posted April 18, 2006 Author Share Posted April 18, 2006 Ok...you can put the nerf bat away. I bought the part....and Jaimie says high. Link to comment Share on other sites More sharing options...
nipper Posted April 18, 2006 Share Posted April 18, 2006 Ok...you can put the nerf bat away. I bought the part....and Jaimie says high. hehehe but i LIKE the nerf bat, better then my wooden cane nipper Link to comment Share on other sites More sharing options...
Gnuman Posted April 18, 2006 Share Posted April 18, 2006 You guys owe me a new keyboard. I just spit coffee all over this one. . . Link to comment Share on other sites More sharing options...
nipper Posted April 18, 2006 Share Posted April 18, 2006 You guys owe me a new keyboard. I just spit coffee all over this one. . . i'll loan you my nerf bat nipper Link to comment Share on other sites More sharing options...
Mike_N_Austin Posted April 18, 2006 Author Share Posted April 18, 2006 You guys owe me a new keyboard. I just spit coffee all over this one. . . Ok..so what is the story on this seafoam stuff ? Link to comment Share on other sites More sharing options...
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