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

[d1giPhux]

Okay, so here is the deal. Installed the MSD coil on my 99 Subaru Legacy GT. Soldered all the connections. Everything ran fine, except when hitting 70MPH or so in 5th gear, it will flick the CEL light on. I don't notice any shuttering or anything going wrong, it just trips the CEL light.

Got the CEL code read, and its coming up as p0303 and p0304, cylinders 3 and 4 misfires.

I took the MSD coil off and put the stock coil back on. Re-soldered all the connections and wrapped them proper. It still seems to run fine, but is now throwing codes p0303 and p0304 still. This was NOT happening before the MSD install.

Not sure what may have gone wrong, but I think swapping the ignition coil caused something to trip the CEL lights. I've reset it multiple times and it keeps tripping the light. The car doesnt shutter or do anything weird that I notice, it only trips the light.

Looking for some suggestions as to what I can check? I'm guessing this is some weird type of electrical error, or something else that may have gone bad during using the MSD coil. Any help would be greatly appreciated!

Edit: A bit more info. I'm running the STOCK coil with 8mm Magnecore wires. Everything was working fine until installing the MSD and running it for about a week. It threw the CEL code right after I installed it, and now its throwing it with the stock coil as well. NOTHING was wrong before. So its either related, or a complete coincidence.

[d1giPhux]

Anyone have any ideas of what I should check? Anyone know if cutting the stock coil harness / rewiring it could have caused this??

[d1giPhux]

Gonna try a couple things today and try to sort this problem out:

-Replace plugs with new NGK V-Powers
-Clean spark plug wire ends and re-lube with dielectric grease
-Clean main ground wire and apply dielectric grease.

Hoping one of these things solves the issue.

Its not so much an issue of the car running badly, its just annoying because it keeps tripping my CEL light. The car itself runs fine, which makes me think its something minor that occurred after installing the MSD coil.

Any other tips or tricks would be greatly appreciated! I'll be posting pics later of what I've done and what I find.

[d1giPhux]

Okay, so this is what I did:

- Removed Air filter and Cleaned MAF with electrical cleaner (i don't suspect this is the case, just figured id do it anyways)
- Replaced spark plugs. All were white/tan colored and in decent condition. Gap wore to .46 on all of them. (doubt this caused CEL)
- Removed coil, cleaned surface where the coil grounds to body of the car. Re-tightened coil down properly. Proper ground.
- Reset ECU by removing battery cables for 2 hrs.
- Also tested the plug wires for continuity(??) and they seemed to give a weird reading. Not sure what to think of it. Read .02V

CEL is off, took it out for a test drive on highway to see if I could make it trip the CEL. Nothing so far.. I'll keep this thread updated if it trips it, and when it does.

[Huffer]

I would have swapped the wires to a different cylinder to see if the misfire moved to that cylinder.

[Dead91silvia]

^ swapping the wires sounds like a good idea if you have the same problem.. I have a miss fire code for cyl4 that pops up on my BH when I do a hard 80-100mph pull on the freeway, but thats it.

[d1giPhux]

^ thats basically what was happening on mine. So far.. no CEL. I think the big thing here people are missing is that the coil needs to be clean on the bottom and making a good ground connection through the screws / base of the coil. Not calling this one dead just yet.. still waiting to see if it ever comes back. Hope it wont. If it does.. i'll try switching the wires around.

[d1giPhux]

:smt013 BAD NEWS.. CEL light came back on. I'm really wondering WTF causes this. It didn't happen until pulling the coil / plugs, and now it does it every time i put the car on cruise control at 70MPH in 5th gear and cruise for about 2 miles.

Is it possible that a minor gasket leak in the exhaust could cause this? The car really does NOT act weird at all.. it just keeps tripping the CEL light.

So.. I'm back at square one.

Anyone know any good tests for testing the spark plug wires? Anyone know where to get some new magnacores if I DO in fact need to buy new ones??

[Huffer]

Did you try my suggestion...

[d1giPhux]

I did not yet, because every time i gotta pull the wires i have to pull the batt, airbox, etc. I replaced the spark plugs, and then everything seemed okay for a day or two.. then back to the misfire CEL light going off. I'm going to go get it scanned again, see what cylinders are misfiring now.

If i pull the wires to switch them around.. I need to pull the entire wire I'm assuming right? I'm guessing my wires just randomly are going bad or something.. totally sucks.

Should I use lots of the dielectric grease on the insides of the plugs and such when connecting them back up?

[d1giPhux]

Update: Was driving around a couple of minutes ago, and once again the CEL was flashing and setting off new codes. Looks like I'm getting misfires on ALL the cylinders. P0301, P0302, P0303, P0304. Something definitely NOT RIGHT here.

I have a feeling its not the wires.. its gotta be some weird grounding issue or something.

Does anyone know how hard it is to pull the main ground off the engine that runs from the battery? Looks like its attached to some weird bracket.. not sure if cleaning this up would help or not.

Need some help here!

Here is what I know:

-The Coil IS good.
-The wires WERE good before this started.. not sure if they are or not now.
-Misfires seem to occur when driving on the highway, and usually while using cruise control.
-I was told a while back that i had a MINOR leak between the cats because the gasket was getting worn away. Could this cause it?

[d1giPhux]

Tested the wires last night using soapy water and sprayed them while the car was running. No arching out, or any sparks. Pretty sure the wires are good..

[Huffer]

Has to be your connection then between your harness and the coilpack. It's what you cut/spliced soldered.

[d1giPhux]

Argh.. hope not. Never should have cut the damn thing! Not really sure what I can do but re-wire it. Not sure why cutting / re-soldering it would cause this issue.

So.. an exhaust leak couldnt cause this problem? Its really weird.. only seems to happen around 70MPH on cruise. Gonna reset ECU and see what comes up next.

[Garrison]

I'm experiencing intermittent misfire on cylinder 1; and rarely cylinder 3 as well. Perhaps if you find a solution I can apply it to my situation.

[DLC]

After getting a quieter and more restrictive exhaust installed on my 97, I got my first CEL on the freeway. At about 70MPH.

P0301 and P0302.

Interested to follow this and see what happens after I unrestrict some of the exhaust, as this was the first time I'd run the car at that speed with the changed exhaust, but not the first time at that speed with the relatively new car.

[d1giPhux]

I reset the ECU.. and so far, hasn't tripped yet. But I know it will be back.

Going to replace the exhaust gasket soon and hope that may fix it. Not sure what exactly is causing this.. pretty weird. :smt017

[Huffer]

I'm no electrician, but did you check for even resistance on your spliced/resoldered coilpack mod?

[harrymaneuvers]

Just read this... my thoughts:


Misfire on all 4 cylinders means it has to either be timing, fuel, air or spark. Since you were messing with the coil pack, I am going to assume is has something to do with that.


If it is still doing it with the OEM coil pack... then I would be looking at the wire splicing.


The only time I experienced misfires on all four cylinders was after my crank pulley came off... it caused my crank sprocket to have a gap where the woodruff key sits... so it could wiggle back and forth on the crank shaft itself.


I know it sounds weird... but if the problem is intermittent and doesn't seem to be affected by swapping coil packs... take 20 second and reach your hand down to the main crank bolt that keeps your crank pulley (harmonic balancer) bolted to the crank. If it is loose, you just found your problem.


Otherwise, when was the last time you did a timing belt change... I would imagine that the same misfires could happen if your timing belt skipped a tooth or even wore away a tooth... possibly the same with a faulty tensioner.

[d1giPhux]

Timing belt was done a couple years ago. I will check the crank pulley as well. No CEL yet.. but I'm just waiting for it. I know it will be back.

Huffer: I'm not sure how I would check the resistance? Any more help with that? Its probably something i SHOULD look into.

Car is getting some work done on it tomorrow.. gonna take a look at some of this stuff.

Edit: A bit more detail about where the exhaust is leaking. Its leaking inbetween the front pipe (header) and First CAT converter. So basically its leaking right before the first 02 sensor. I'm guessing this may be the issue. Going to replace the gasket.. then drive and report back.

[Huffer]

It's not likely for the exhaust leak to cause a misfire - a CEL perhaps for a misreading O2 sensor.

[d1giPhux]

I dunno, ive been reading around on different forums after some searching.. and seems like random misfires CAN occur when the leak is before the first CAT. Or at least.. thats what some of the ppl's problems i saw were. Gonna replace the gasket anyways as its getting annoying now that my exhaust is louder. Hoping it fixes the problem.

[jkaic]

OP, did you find out what the problem is? I'm having random misfires with all 4 while cruising on the highway too. Replaced plugs, wires, coil, both o2's, patched up my pre-cat exhaust leak and replaced fuel filter but CEL still shows up, usually about 50kms after I reset it. Haven't checked the harmonic balancer yet. Also does your car smell like the cat is burning/sulfur smell? Let me know if you found your solution!

[d1giPhux]

I have not found the solution yet, as I've ran into more problems with my car I've had to fix and havent had the time to complete the exhaust gasket yet.

My car does not smell like the cat is burning / sulfur smell.. if you are smelling that, its because your CAT is going bad and needs to be replaced soon.

[jkaic]

I'd just replaced it a month ago, hoping that by this time i'd have fixed the misfire problem... so i know already that something's heating up and burning my cat :/

[jkaic]

K, fixed it! Turns out I had a bad grounding. Did a DIY grounding to the two strut towers, alternator, starter and TB and no more CELs so far, it's been a week (knock on wood). DIdn't think it would be the solution but hey i'm not complaining. Still smelling the sulfur though, i think it might be the exhaust leak... heh

[d1giPhux]

What do you think had a bad ground? Hopefully it works out for you, make sure to update in a couple of weeks. My car has been down since this issue, so I haven't had time to really drive it. Still fixing the damn brake lines :(

[amgarrety]

Ok, so this may or may not help, but I had a similar experience today and I instantly thought of this thread.

I was on the highway, in 5th gear, at about 70 MPH when my CEL popped on. I instantly checked it and I got a misfire on a few cylinders, and something wrong with the fuel sensor, and some other stuff. But like you, I felt nothing odd, and there were no odd smells, and nothing looked out of place. So I have a friend who works at advance autoparts. He explained it to me, but I only retain the basics. Basically, there are certain fail-safes in the engine that try to alert you when the engine thinks something is wrong. When the motor feels like it has reached it's thresh hold (even if it hasn't actually), even for a fraction of a second, it will throw a bunch of codes. It was funny, his first question to me was if it happened on the highway. That apparently is where it happens most often because you cruise in higher RPMs for longer periods of time.

I had him just clear my codes for me. I haven't had a problem since, but I haven't been on the highway since either, so I can't just go ahead and say it was just nothing.


Some additional info, I have absolutely nothing done to my engine. The most I have done is exhaust with one cat deleted. Other than that, i'm stock.

I'm hoping this can be of even the least bit of help. Although I can't offer much explanation. If you want more detailed info about what happened to my car, I can text my friend and get him to give me the details again.

[d1giPhux]

Thanks for the info man! Yeah.. it could be that. My car has been back on the road (sort of) for a couple minutes the past couple days.. and no CEL coming up. Once my car is fully fixed, i'll report back. Still need to fix the exhaust gasket issue as well.

[mrpyb]

My car threw 3 & 4 misfire codes for about 6 months before I finally did something about it. For me it was the knock sensor, replaced that about 2 months ago and haven't had a CEL since!
good luck.

[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. https://sl-i.net/FORUM/images/imported/2012/08/IMG_20120818_110519-1.jpg

[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!! :smt030 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! :smt005

[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. :smt023

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. :smt023 :smt030

[d1giPhux]

putting this new knock sensor in is driving me fucking crazy!! ARGH! :smt013

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! :grin:

[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:
https://sl-i.net/FORUM/images/imported/2013/03/IMAG0027_zps461d74d7-2.jpg




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...

[prodriver1]

I work on a LOT of subarus in my town and almost all of them needed a new knock sensor, hesitation off the line, misfire codes, flashing CEL at higher speeds, all due to bad KS. that and heat shields needing to be cut off are the 2 most common things i do. and getting the KS on is always a faff, they never want to thread back in correctly. nothing needs to be moved out of the way for the KS job, just a really long extension and you'll have it.

[d1giPhux]

Yeah, im glad i got it all fixed! The knock sensor fixed all the random CEL misfire codes I was getting! Good to know that this is a common problem!

[Garrison]

I wanted to update you guys a bit more on my situation.

I further torqued-down my knock sensor, prior I had it at 12ft/lbs and I gave it a nice 3/4 turn with a rachet and even though it feels like it's going to slip at any moment, I sunk it in there tighter.
IMMEDIATE IMPROVEMENT.

That's really insane that it makes -that- much difference in the functioning of the engine. As Prodriver was saying, smooth idle and it takes off from the line much much easier/smoother now.

Thanks you guys for the help. 12mm socket + 10" extension = problem solved (for now :P)

[d1giPhux]

Yeah, out of all the threads I read about it, the knock sensor is technically supposed to be torqued to 17ft/lbs. I tightened mine to 16ft/lbs and its fine. Not sure what the actual torque specs are though, i think its 17.4 or something like that if i recall correctly.

[prodriver1]

good to hear guys :smt023 :grin: , problems like this can be super mysterious as you cant SEE anything broken, this will definitely be of huge help to other suby guys like us. :smt007

[zoomzabba]

After long pondering my misfire codes, I changed the plugs to NGK IX(3&4 looked like they got skipped last time) and cleaned the wires and terminals . Didn't fix the issue. Considering the addition of a 2.5" exhaust; i may have added another factor. Saw this thread; found a nice crack all the way around and hairline on top of the knock sensor. Just installed and reset ECU. Have to get on the highway to test. If not the fix, NGK wires and MSD pack are in the mail as we speak.

[Grimmrican]

What car did u get the msd coil pack from?

[98legwag]

What car did u get the msd coil pack from?
Most likely a Neon. It does not work on the 3rd gen. The wiring going in is different. 2nd gens have a 3 wire plug similar to the Neon. From what I have read the 3rd gen has a 4 wire plug.

[Grimmrican]

Yea I was looking into it at work for my third gen and a 02 neon. They look the same but the part numbers were different so maybe something inside changed up

[d1giPhux]

Report back if it was in fact your knock sensor. I bet it was. Mine started throwing misfires on 3, then 1 and 3, then all 4, etc. Got worse and more mysterious over time. Turned out it was the knock sensor the whole time. I get way better MPG now too!

[Garrison]

I was still getting random misfire codes with my replacement sensor, and when I went to tighten it up, the bolt slipped and I figured a die would do to fix it it. I tapped the threads, and cut the head to 45degrees. Still no luck, it simply wouldn't thread!

So I went to NAPA and got a m8x1.25mm bolt which was about 1/8" longer than the oem bolt. I threw a slim washer on there and finally got it to bite, tightened it down, and now finally am free of a loping idle.

Will update with road testing! :grin:

[d1giPhux]

Wow, sounds like you went through the nightmare scenario with your install! Glad you got it sorted.

I'm pretty sure the knock sensors are supposed to be tightened to 16 ft/lbs. Maybe you over-tightened it initially? Either that, or the threads were just gone to begin with. I hear this can be common.

Hope it works out for you!! Keep up updated! :smt023

[Garrison]

No luck!

Am still getting random misfires. Probably crank sprocket time :/

[Boozeboy89]

This has been a very helpful read :razz:
I have been living with this problem for 16000 miles now in my 98 Legacy!
i bought a replacement motor a year ago with 175k and has been a fight since day 1
gave up after a while of replacing and checking parts and feared it was internal engine failure
eventually i got used to it, i dont really need to go over 70 and im still getting 28 mpg!!!


so far i have
-replaced plugs - Platinums
-wires - OE
-coil - from my parts wagon
-ran compression tests (150 all around)
-new injectors
-93 octane fuel brought the misfires from 65 to 70mph
-full synthetic oil 10w30 - really quiets down the piston slap, but still misfires

I am definitely going to check and replace my knock sensor tomorrow!!

[Garrison]

Soooo... after about 300 miles, my knock sensor seems to have done the trick. I've only gotten 2 CEL codes (still random misfire codes) but the ECU will allow me to get an inspection now which is all I really ever cared about in the first place, haha.

[d1giPhux]

Hell yeah! Glad to hear another success story!

Boozeboy: post back and let us know if it fixed your problem as well. i hope you are kindly pleased!

[Boozeboy89]

Hell yeah! Glad to hear another success story!

Boozeboy: post back and let us know if it fixed your problem as well. i hope you are kindly pleased!



Knock sensor didn't fix it, no change

I swapped the ECM from my parts wagon (97 outback)
ITS FIXED!!! :smt023
I can go over 3000 rpm with no misfire codes. So much better!
now it just throws a code for the EVAP purge - insufficient flow
which my wagon had a completely different EVAP system in it so its understandable
I can live with that since we don't require OBD2 state inspections older than 1999