CEL for Misfire on cylinder (P0303). Confused.

[DSM IN MN]

My car has been giving me some problems recently with running lean after certain time spent at WOT. Now while dealing with that problem, the one I am about to explain arrived.

Friday August 31st I was on my way to get my senior pictures taken for school. I got in my car and let it warm up for maybe 10-20 seconds (MAYBE), then I was off. I noticed when I went about 70% throttle to pull off of the road to my house, my car had a hesitation AFTER already accelerating; so I was already going 20-25 MPH then the car felt like it missed, or all of the power went away for a quick second. Then it was fine.

As I was driving on the highway, 17 minutes into the 25 minute drive my car's narrow-band gauge goes to lean. Then the CEL comes on. Mean-while I am like "Ok, WTF is going on now?". Usually when my car runs lean it isn't followed by a CEL so quickly. I knew something was up. I will post a video I took that morning.

Please note that what I was trying to explain in the video about the narrow-band gauge is that instead of the gauge showing one single light to represent "lean" or "rich" or whatever the middle is, the gauge would show multiple lights at once; like a little bit of the orange lights leading to lean, and some yellow, and a tad bit of green. Then it would almost pulsate back and fourth a little bit. I failed to show this in the video.

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Now for the last few pictures, we did them at my dad's shop with my Talon. So while I was there I checked the CEL code. It came out to be P0303; misfire on cylinder three. I assumed bad plugs. I had planned on changing them anyways so I figured now would be the time to do it. I started to head home. Here is a video of what the car sounds like as I accelerate.

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Since then I changed the spark plugs. Right after that nothing changed. I pulled them out and gaped them to .028. That as well did not change anything. I decided to check if all the plugs were getting spark. I took all of them out, connected them to the plug wires, and turned the car over for a few seconds. My friend who was with me said they were all sparking. So I tested the volts at the injector clip on cylinder 3; while running, the volts got up to around 7. Whether that is normal or not, I do not know. I did try to look it up with no luck. Maybe I just didn't try hard enough.

Any who; I pulled the injectors out. I had a home made injector cleaner I made a few months back. I cleaned the one which I believed to be the cylinder 3 injector. A little bit of black stuff came out. Then the "tool" failed. I just threw it away after epoxy wouldn't help.

So this morning after battling with allergies and being just down right dizzy, I went outside and put everything back together. I started the car with no plan on seeing any different results. To my surprise the car seemed to run fine. It was cold from not running for two days though. After a few seconds it was right back to missing.

I revved it and well...I took another video. You can tell I wasn't too happy.

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Before I started typing all of this, I disconnected the battery completely (positive and negative terminals). I do not expect this to do anything. However if it does, I am going to assume there is a problem with my ECU and/or wiring and/or sensors. I will update this thread when I re-connect the battery and take it for a drive.

School starts tomorrow and I DO NOT want to drive the car for the 20 mile trip to school, then to work and back home. I do NOT want to be stuck riding with my sister in her '05 Dodge Neon w/SRT design package for more than a week though! You cannot exactly blame me!

Does ANYONE have any suggestions on what to replace or look at besides plug wires and an o2 sensor? (The o2 sensor is more for my running lean issue, but I figured I could kill two birds with one stone, possibly).

Thanks for reading through my book!

To add to this; as I figured, removing the battery didn't help any. It did on start up, but after that it went back to doing what it was doing before. I have a few videos to show that I will upload when I can.

 

[gstmine]

hay ran your engine to operating temp & check the compresson on all cylinders & compair then all. you might also have the coil pack going out

 

[Spoolin92GSX]

Your second and third videos seem to have been removed from Photobucket, but you said "sounds like a Subaru" in your first video. I strongly suspect your coil pack is to blame. I'm assuming it does this at idle also, if so (I know this isn't recommended but it's a quick way to diagnose) while it's misfiring/sounding like a Subaru, pull one spark plug wire off and see if the engine runs different/dies. If it's reading a misfire on #3 then #2 should be dead also, if it's the coil pack. I had one go intermittently bad so I know how frustrating this can be.

 

[DSM IN MN]

Your second and third videos seem to have been removed from Photobucket, but you said "sounds like a Subaru" in your first video. I strongly suspect your coil pack is to blame. I'm assuming it does this at idle also, if so (I know this isn't recommended but it's a quick way to diagnose) while it's misfiring/sounding like a Subaru, pull one spark plug wire off and see if the engine runs different/dies. If it's reading a misfire on #3 then #2 should be dead also, if it's the coil pack. I had one go intermittently bad so I know how frustrating this can be.

That would be Photobucket doing its usual B.S. when it comes to uploading videos; no surprise. Really all it was showing was the sound of the car.

Any who, I have a new coil sitting on my kitchen table (I work at NAPA so parts are easy to get). As of now the coil is charged to my dad (payday is tomorrow), and the coil is $71.36 or something..my cost. Add $105 to it for every day customer cost.... I'd rather not put it on and have it NOT be the problem.

I can almost bet that's the problem but, it only says cylinder 3..

 

[jayson427]

Had similar issues not to long ago. turned out to be my coil pack. Get a coil and if it still acts up just take it back.

 

[DSM IN MN]

I replaced the coil that had the number 3 cylinder on it an NOTHING. There was no change. It seemed to idle a TAD bit more smooth, but as it exited open loop mode it just went right back to where it was before.

Also, it seems at higher RPMs it doesn't happen. Now if that is because it actually isn't happening or just because I cannot hear it, I do not know.

Had similar issues not to long ago. turned out to be my coil pack. Get a coil and if it still acts up just take it back.

I assume you are speaking about an N/T here.. The same doesn't apply. I work at a parts store (NAPA), and you cannot return things once they are installed on the car. I honestly dislike people who try to and/or think they can. It just isn't how you do things.




I ended up deleting the videos I had planned on uploading for more room on my SD card on my phone. Now if any of you would like to hear the video of the car starting after the new coil; let me know. Otherwise it is staying on my phone until probably next week; then I'll just delete it.

 

[Spoolin92GSX]

At higher rpms you're probably ticking over to open loop. Do you have a logger to check what the o2 sensor is doing, ie specific voltage output? If it's only happening in closed loop I'd be willing to bet your o2 sensor is toast.

 

[nickk90]

do you have a scan tool that can show live data?
what are the fuel trims?
put a screwdriver to the injector and listen to see if you can hear it opening.
If your fuel trims are lean then its probably that injector not injectiong fuel into that cylinder.
check that the ecu is sending power to the injector and that it has control over it

 

[delta448]

You have a fuel injector or injector control circuit problem.

It's only showing lean because the misfiring is sending unused oxygen into the exhaust. The cylinder could be misfiring because of too much fuel, but an O2 sensor will still read it as lean because of unused oxygen.

Swap the #3 injector around to another cylinder and clear the code. If the misfire DTC becomes set for the cylinder you swapped the #3 injector to, then all 4 injectors will need cleaned and flow tested. If the misfire stays at cylinder 3, you have either a bad injector resistor pack or a shorted/broken wire between the resistor pack and injector or ECU and injector.

 

[nickk90]

You have a fuel injector or injector control circuit problem.

It's only showing lean because the misfiring is sending unused oxygen into the exhaust. The injector could be misfiring because of too much fuel, but an O2 sensor will still read it as lean because of unused oxygen.

Swap the #3 injector around to another cylinder and clear the code. If the misfire DTC becomes set for the cylinder you swapped the #3 injector to, then all 4 injectors will need cleaned and flow tested. If the misfire stays at cylinder 3, you have either a bad injector resistor pack or a shorted/broken wire between the resistor pack and injector or ECU and injector.

If it was a rich misfire the o2 would read rich. Along with that unused oxygen you will also have unburned fuel leading in a rich o2 and high fuel trim. But I'm with out on it being a injector or injector circuit problem

 

[Diamond Star Werks]

It is also very possible that you have a vacuum leak. It can either on the injector o-ring that goes into the had or at the intake manifold. This would explain why you can't hear/feel it at higher rpms as vacuum leaks can be like that. Would also explain your lean condition.

Check for vacuum leaks. Use starting fluid, brake fluid, carb cleaner. If you spray over a vacuum leak thats big enough idle should change. If it is a small leak sometimes it won't change rpm much but it will always change o2 reading to rich.

 

[nickk90]

It is also very possible that you have a vacuum leak. It can either on the injector o-ring that goes into the had or at the intake manifold. This would explain why you can't hear/feel it at higher rpms as vacuum leaks can be like that. Would also explain your lean condition.

Check for vacuum leaks. Use starting fluid, brake fluid, carb cleaner. If you spray over a vacuum leak thats big enough idle should change. If it is a small leak sometimes it won't change rpm much but it will always change o2 reading to rich.

This is also a good possibility. A BLT would be the easiest way to find a leak. Look close around the #3 runner where it mount to the head and around the injector. I would defiantly stop chasing spark though

 

[DSM IN MN]

At higher rpms you're probably ticking over to open loop. Do you have a logger to check what the o2 sensor is doing, ie specific voltage output? If it's only happening in closed loop I'd be willing to bet your o2 sensor is toast.

No, I have no form of logging. I have a scan too, that's it though.

do you have a scan tool that can show live data?
what are the fuel trims?
put a screwdriver to the injector and listen to see if you can hear it opening.
If your fuel trims are lean then its probably that injector not injectiong fuel into that cylinder.
check that the ecu is sending power to the injector and that it has control over it

Yes I have a scan tool. I will check on this stuff tonight after work. However I do recall nothing unusual while viewing live data the other day.

You have a fuel injector or injector control circuit problem.

It's only showing lean because the misfiring is sending unused oxygen into the exhaust. The injector could be misfiring because of too much fuel, but an O2 sensor will still read it as lean because of unused oxygen.

Swap the #3 injector around to another cylinder and clear the code. If the misfire DTC becomes set for the cylinder you swapped the #3 injector to, then all 4 injectors will need cleaned and flow tested. If the misfire stays at cylinder 3, you have either a bad injector resistor pack or a shorted/broken wire between the resistor pack and injector or ECU and injector.

I did TRY to swap all of the injectors around, but still ended up with the P0303 code. Granted I could have accidentally put them back into their previous locations on the fuel rail. I'll make aure to swap adleast the number 3 for sure tonight. That should help figure it out for sure.

If it was a rich misfire the o2 would read rich. Along with that unused oxygen you will also have unburned fuel leading in a rich o2 and high fuel trim. But I'm with out on it being a injector or injector circuit problem

I myself am hoping it isn't a fuel injector problem. Lol If it is, it is though.

It is also very possible that you have a vacuum leak. It can either on the injector o-ring that goes into the had or at the intake manifold. This would explain why you can't hear/feel it at higher rpms as vacuum leaks can be like that. Would also explain your lean condition.

Check for vacuum leaks. Use starting fluid, brake fluid, carb cleaner. If you spray over a vacuum leak thats big enough idle should change. If it is a small leak sometimes it won't change rpm much but it will always change o2 reading to rich.

Is it possible to have formed a leak? When I installed my hard IC piping I did a BLT and nothing was leaking.

This is also a good possibility. A BLT would be the easiest way to find a leak. Look close around the #3 runner where it mount to the head and around the injector. I would defiantly stop chasing spark though

I'll see what I find out tonight then go from there.

 

[delta448]

If it was a rich misfire the o2 would read rich. Along with that unused oxygen you will also have unburned fuel leading in a rich o2 and high fuel trim.

This is misinformation.

Q: Why do we call them oxygen sensors?
A: Because they measure oxygen content. Not fuel. Not hydrocarbons. Just oxygen.

If you take in air, don't burn it, but push it through to the exhaust, the OXYGEN sensor will see a high level of oxygen and it's voltage will drop, falsely indicating a lean mixture.

How Does the Oxygen Sensor Work

The voltage signal is proportional to the amount of unburned oxygen in the exhaust. When hot (at least 600. F), the zirconium dioxide element in the sensor's tip produces a voltage signal that varies according to the difference in oxygen content between exhaust and outside air.

The higher the concentration of unburned oxygen in the exhaust, the lower the differential across the sensor tip and the lower the sensor's voltage output. The sensor's output ranges from 0.1 volts (lean) to 0.9 volts (rich).

OXYGEN SENSORS

The difference in oxygen levels between the exhaust and outside air within the sensor causes voltage to flow through the ceramic bulb. The greater the difference, the higher the voltage reading.

An oxygen sensor will typically generate up to about 0.9 volts when the fuel mixture is rich and there is little unburned oxygen in the exhaust. When the mixture is lean, the sensor output voltage will drop down to about 0.2 volts or less. When the air/fuel mixture is balanced or at the equilibrium point of about 14.7 to 1, the sensor will read around .45 volts.

How oxygen sensors work

When an engine has more fuel than it needs, all the oxygen in the cylinder head is consumed and the resulting exhaust gases contain almost no oxygen. This usually causes the sensor to generate a voltage of greater than 0.45 volts. If the engine is running too lean, all the fuel is burned, and the extra oxygen remaining flows out into the exhaust manifold. The oxygen sensor detects the extra oxygen and the voltage signal will drop to below 0.45 volts.

http://www.cartechbooks.com/techtips/wideopenthrottletuning/

Remember that misfire conditions appear as lean to a wideband oxygen sensor due to the large amounts of unburned oxygen present in the exhaust.

http://www.3si.org/forum/5514128-post2.html

http://forums.corral.net/forums/10699559-post8.html

http://forums.evolutionm.net/7212368-post6.html

http://forums.turbobricks.com/showpost.php?p=1558685&postcount=2

 

[GSTurbo1]

can you unplug all your wires from coil pack then plug them back in, mine had an injector wire pulled loose when mine ran like that. But I have a stand alone that and the wires like to get pulled loose.

 

[DSM IN MN]

My NGK plug wires came in today at work. I put them in and as far as I can see the problem is solved. I cleared the code and it hasn't come back so case closed. Thank you all for the help!

 

[jayson427]

I replaced the coil that had the number 3 cylinder on it an NOTHING. There was no change. It seemed to idle a TAD bit more smooth, but as it exited open loop mode it just went right back to where it was before.

Also, it seems at higher RPMs it doesn't happen. Now if that is because it actually isn't happening or just because I cannot hear it, I do not know.



I assume you are speaking about an N/T here.. The same doesn't apply. I work at a parts store (NAPA), and you cannot return things once they are installed on the car. I honestly dislike people who try to and/or think they can. It just isn't how you do things.




I ended up deleting the videos I had planned on uploading for more room on my SD card on my phone. Now if any of you would like to hear the video of the car starting after the new coil; let me know. Otherwise it is staying on my phone until probably next week; then I'll just delete it.

im glad you work at a "parts store" n/t or not engine problems are similar with any car yeah theres alot that is different but the basics are the same. especially with a misfire.

 

[DSM IN MN]

im glad you work at a "parts store" n/t or not engine problems are similar with any car yeah theres alot that is different but the basics are the same. especially with a misfire.

The problem was solved. ...with my "parts store" parts. Sorry, but I couldn't resist.

 

[Spoolin92GSX]

Well, NGK isn't a "parts store" brand. Sorry, couldn't resist Glad to hear you found the problem!

 

[delta448]

My friend who was with me said they were all sparking.

^Fire this guy.

Glad you got it fixed!

 

[DSM IN MN]

Well, NGK isn't a "parts store" brand. Sorry, couldn't resist Glad to hear you found the problem!

Hahaha, alright. Whatever you say!

^Fire this guy.

Glad you got it fixed!

Lol, I've been considering it. And thanks!