P0303 & P0304!! Random Misfires.... its knock sensor! FIXED!

[d1giPhux]

I replaced the exhaust gasket as of today.. no CEL so far. We'll see how long this lasts. Took it on the highway and did the test to see if I could get the CEL to come on. Nothing. Hoping this fixed it! *knock on wood*

[AustinNW]

I have a 3 & 4 miss fire code in my 98 2.5 bd also. I have reset it a few times and it seems to come back on the freeway at 70+ , especially while on cruise control. I've had it happening for almost a year but just learned how to turn it off by removing battery last week and just had the code checked for the first time today. It has ngk plugs with about 15k on them some kind of schucks wires from the same time. New fuel filter, new cone filter post missfiring. It does have 234k going to try some of these things suggested.

[AustinNW]

Went to pull & save in Spokane today and tracked down a coil pack and associated wire/plug from a 99 neon with 123k miles on it. I don't know how much I expected to pay but I almost laughed when the girl told me $3 for the coil. Took a hacksaw to my stock coil to remove the mail connecter from it, wasn't the prettiest job but now that I know what the inside looks like I could do it cleaner. Soldered the 3 wires to the male coil connecter and hot glued it to seal it up. Glad I was able to make that work because I did not want to cut my harness.

Seems to run smoother, have a little more power, and have faster throttle response. So far no more cel but it's only been 10 miles so we will see on that. It also seemed to make my already horrendously rattling cats/heat shield or something in my exhust slightly worse. I am thinking about getting the accel coil pack off eBay for $39. I've read about msd results but none from that one so I am still undecided.

[d1giPhux]

Well.. after having this be gone for a while, it has returned. Same as it was. 70mph on cruise on freeway. Threw PO303, and PO304 today.

Replace spark plug wires last weekend with new NGK, didn't fix the problem.

Wondering if it could possibly be timing belt? I hear some squeaking sounds and such, and know for a fact there was a hole in the timing cover for a while. Maybe one of the idlers is in bad shape?

Any ideas what I should try now?

[afterbangin]

You may want to check your plugs and make sure none of them are fowled by oil or anything. Our cars really like OEM plug wires but I've switched over to the NGK ones with NGK Iridium plugs and my Legacy seems to like it. If you need a good deal on some plugs, I have a brand new set of the Iridum IX that I didn't use because I opted for the Laser Iridium since they have a longer change interval. Even though I just love changing plugs on the EJ25D, I decided a few more bucks was more it

As posted above, a knock sensor could be a problem put they usually throw a code before they completely take a dump on you. I would put an OEM coil pack back on, new plugs, reset the codes, and see what happens.

[afterbangin]

Also, a worn idler bearing wouldn't cause a misfire. If your timing is off, that definitely could. You may want to take the cover off and see if your tensioner is tight on the bracket and your belt isn't loose. The belt could have jumped a tooth without tossing the belt completely off. With an EJ25D, as you probably already know, a timing belt problem is not something you want to deal with.

[d1giPhux]

It didn't jump a tooth, i've had that issue before.

Also, i replaced the plug wires with brand new NGK's a couple weeks ago. Didn't fix the problem. Not really sure WHAT is causing this, but the car isn't acting abnormal AT ALL. It just randomly comes on sometimes while cruising around 70mph on the highway. No stuttering, no nothing. The car runs perfect, but it still throws the CEL light randomly. Went away for months, and now its back!?

[Odycee]

When you speed up to 70 mph, it puts a large load on the electrical system and the ECU monitors the required voltage to keep up with the load. Since you messed around with the electrical system, you changed the resistance path to the coil even though you thought you put it back to the original condition. Therefore, the ECU flashed the CEL to tell you it's NOT a permanent code but rather voltage out of range. As you stated, it runs fine until it hits 70 mph.

Instead to try to repair to resolder the original wires, go to dealership buy the wires to replace it is your best option.

[d1giPhux]

Cant really replace the wires, as these are the wires coming off the engine harness. I would have to replace the whole engine harness. I sort of have the feeling that is where the problem is coming from. However, now I actually had a first bucking surge from a backfire as of yesterday. At full WOT it kicked REALLY friggin hard and was not cool at all. However after bucking once, it went back to driving perfectly. Not sure what the heck is causing this, but its really getting on my nerves I cant figure it out.

Either way, I COULD re-solder the wires coming from the harness going to the coil pack plug, but they seem pretty well soldered to me now and I don't think it would make much of a difference. The connections ARE good. Only throws CEL code when cruising around 70mph for a while. And the bucking problem has only happened once in all this time (months).

I'm going to clean the MAF and hope that may have something to do with it. However, if the maf was dirty I'm sure I would be getting other symptoms as well!

[98legacygt22]

Give your knock sensor a check, if it even has the tiniest crack then that is most likely the problem. Mine was throwing random miss fire codes and it was due to that, same with my buddies legacy.

[d1giPhux]

Really? Is it easy enough to replace? When did yours give misfires? Did you notice the engine running rough at all when it 'misfired'??

[Huffer]

Knock sensor is an easy check/fix. I know when I accidentally exposed the knock sensor on my car to water (removed the scoop blanking plate cos I thought it was cool) the car ran like crap. I also found a few random misfires even when it was running fine.

There's plenty of threads on installing/removing the knock sensor.

[Garrison]

I'm going to try 2 things before I resign myself to replace the coilpack.

-New knock sensor
-New PCV valve (I think this could actually turn out to be legit)

Obviously I'll do them one at a time to see which, if either, works.

[98legacygt22]

Yeah this is what mine looked like when I went to go replace it, I still have a miss fire but it's not all 4 cylinders like it was before. Previous owner put 2.5 plug wires on the car and they werent contacting correctly, also I need a rear o2 sensor I think.

[d1giPhux]

I think you guys were really onto something! finally my car has thrown a knock sensor code. Pretty sure that the knock sensor must be going. The car now randomly throws misfire codes for multiple cylinders and a knock sensor code! you were definitely onto something. This may be the reason for my TERRIBLE gas mileage all along too!

I'm going to replace the knock sensor this weekend, and hoping it sorts it out.

Any tips on replacing the knock sensor?

Just wanted to keep this thread updated in case anyone runs into this in the future. I'm pretty sure it must be the knock sensor!

Thanks guys! I should have listened sooner!! Hoping the new knock sensor will fix this issue! Now I just need to figure out how to align the knock sensor wire, as it says 45 degrees to the engine. Not sure which way the wire should be.. but I will try to see how mine is currently. Pretty damn hard to see down into that part of the engine!

[Grimmrican]

Something I learned about knock sensors is to try some seafoam. Pour it down the vacuum hose while running. Hopefully u guys know what seafoam does. Seafoam will help break up all the carbon build up in the engine. Too much carbon will cake up and make the smallest ping sound like u have a nasty knock to the knock sensor. I tried seafoam in my 95 bk 246k miles and it worked (Results may vary) but I'd rather go spend 12$ and try it out than go spend something way more expensive. Hopefully it'll work out for u guys

[d1giPhux]

My engine doesn't actually ping, or run weird at all. I've seafoamed my engine and nothing ever came out.. probably because it was recently rebuilt a couple years back. Good tips though for those who may find it useful!

I'm pretty sure my sensor must just be cracked like they usually are on these engines. Going to pull it this weekend and check.

Also, i bought my knock sensor on ebay for $8 shipped. They are incredibly cheap as long as you dont get them OEM!

[Garrison]

I'll be doing the same (still getting misfire codes on cylinders 1, 2, 4).

Make sure you don't torque it down too much, it causes the sensor to be extra sensitive (or to crack)

[Grimmrican]

I'll be doing the same (still getting misfire codes on cylinders 1, 2, 4).

Make sure you don't torque it down too much, it causes the sensor to be extra sensitive (or to crack)

There should me an actual torque spec around here somewhere >_>

[d1giPhux]

Its 15ft/lbs as far as I've seen everywhere. Which isn't much. I'll just make sure to get it down but not torque the hell out of it. After all, its plastic. I heard that the torque amount also has to be correct or the sensor may not make a proper reading on the engine. I have an old torque wrench (one with the needle) and I will use that to torque it down. Hoping to get to this sunday when I'm not so damn busy! Hopefully it won't be a total pain.

Anyone have any tips for getting the bolt back into the hole without dropping it off into the engine bay? It seems like quite a ways down to be fumbling with.

[d1giPhux]

putting this new knock sensor in is driving me fucking crazy!! ARGH!

Seems like the bolt wont thread into the hole properly.. and I'm hoping the damn hole isn't stripped or something. Maybe I just need to use a die on the bolt or something, as the end threads may be worn :smt012

[d1giPhux]

Finally got it! What a PAIN!

I bought a m8x1.25mm die from NAPA and ran it over the threads on the bolt. Then filed the end to a 45 degree angle a bit. Pushed on it while screwing down and it worked out. WOOHOO.

Weird question: I disconnected a coolant hose going to the throttle body/intake manifold area. Does this mean there is going to be a pocket of air in the line now? How can I bleed the system easily? Run the car with the radiator cap off? I had to disconnect it so that I could move it out of the way a bit.. annoying, but it had to be done.

Thanks.

[d1giPhux]

After driving the car.. the check engine light has NOT come back on. And i did some highway miles and was NOT able to trigger the misfire at 70MPH. This is AWESOME news. All along it must have been the knock sensor failing!!

Going to keep driving around and will post results. But so far.. this is looking like it fixed the issues I was having with misfires on random cylinders, and fixes the knock sensor code that eventually showed itself!!

[Garrison]

I'm about to try this, and I was wondering if you had any tips for going about it.

I just took a look at it, and if you disconnect the throttle cables it seems like you could slide a socket and extension down through that opening without removing the intake manifold or the throttle-body. Is this correct?

[r3v_v3ng3]

If you want more room, just unbolt the throttle body and move it aside. You dont have to take out the coolant lines just leave them on. Of course disconnect the throttle/cruise cable. I never had problem reusing throttle body gasket (many times). This way you have more room to connect disconnect the wire

[Garrison]

If you want more room, just unbolt the throttle body and move it aside. You dont have to take out the coolant lines just leave them on. Of course disconnect the throttle/cruise cable. I never had problem reusing throttle body gasket (many times). This way you have more room to connect disconnect the wire

Sounds great, thank you kindly!

[d1giPhux]

Don't bother un-doing the throttle body. Its un-necessary. All i needed to do was disconnect 1 rubber line that was in the way (had coolant in it) and then get at it with a 10" extension and 12mm socket.

Once you take a look at it, you will realize its not that hard. Just a pain to get at.

Also, to get the bolt back in what I did was line up the sensor on top of the hole, and then take a piece of paper and put it in my socket on top of the bolt so that the bolt sits tight inside of the socket and wont drop out. Unless you have magnetic sockets this will be the way to go. I actually used a paper towel and just folded it over the top of the bolt and then jammed it into the socket for a tight fit.

You will definitely want to have a magnet on hand in case you drop the bolt or something.

[Garrison]

You guys nailed it with the supporting information of switching out the knock sensor, thanks!

Little sucker had a nice crack in it too:





The soob runs much smoother now. I think I'll still have to replace the crank sprocket and woodruff key eventually though.

[d1giPhux]

Glad you were able to fix yours as well! Awesome! After driving with a new tank of gas, I'm seriously getting over 40% better gas mileage than I have EVER gotten before! Its insane!

[Huffer]

Nice...