Misfire Thread
Joined: Dec 2007
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Anyone figure out what causes multiple misfire (p300/301/302/303/1399) only at idle? I'm really leaning towards the map sensor/IACV since it doesn't like to idle. If I drive carefully and come to a stop in gear, I don't get the misfire code. If I neutral-coast to a stop that's the only time I get it and even then it's intermittent. Really annoying and nerveracking since it's still in break-in since the rebuild.
Joined: Oct 2010
Posts: 850
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From: Sacramento
I own a 2002 S2K with 103,434mi. So I pulled the engine codes that I was throwing. I have a misfire in cylinder 2 and 4 and a Random Misfire Code as well. The car idles extremely rough and is not driveable! The engine light stays flashing UNTIL I turn the car off. Once the car is off and I restart it, it's a solid code. Okay so this is what I have done so far (holy hell):
1. Checked valve clearance. All valves are within spec.
2. Transferred Spark Plug from Cylinder 2 to Cylinder 1. CEL displayed Cylinder 1 as misfiring when the plug was moved from 2 to 1.
3. Checked Spark Plugs. They looked pretty foul so replaced them with brand new plugs. Now getting ONE check engine light for Misfire in Cylinder 3 ONLY.
4. Checked Voltage of the alternator and it's within spec.
5. Compression tested 200-210 across all 4 cylinders when engine was warm.
6. Swapped Coil Packs and that made zero difference.
I have not:
1. Checked if the fuel may be bad. I have 2 bars of gas and this started when I had roughly 3-4 bars (This has never been an issue in the past).
2. Done a leakdown test.
3. Swapped injectors anywhere.
4. Checked the timing (How could I even check? I do have a bad TCT).
5. MAP whacked.
6. Checked any o2 sensors. Would o2 sensors cause misfiring?
What do you guys think it may be? Thanks for the opinions! Oh and even with the garage opens, it smells like gas horribly.
1. Checked valve clearance. All valves are within spec.
2. Transferred Spark Plug from Cylinder 2 to Cylinder 1. CEL displayed Cylinder 1 as misfiring when the plug was moved from 2 to 1.
3. Checked Spark Plugs. They looked pretty foul so replaced them with brand new plugs. Now getting ONE check engine light for Misfire in Cylinder 3 ONLY.
4. Checked Voltage of the alternator and it's within spec.
5. Compression tested 200-210 across all 4 cylinders when engine was warm.
6. Swapped Coil Packs and that made zero difference.
I have not:
1. Checked if the fuel may be bad. I have 2 bars of gas and this started when I had roughly 3-4 bars (This has never been an issue in the past).
2. Done a leakdown test.
3. Swapped injectors anywhere.
4. Checked the timing (How could I even check? I do have a bad TCT).
5. MAP whacked.
6. Checked any o2 sensors. Would o2 sensors cause misfiring?
What do you guys think it may be? Thanks for the opinions! Oh and even with the garage opens, it smells like gas horribly.
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Joined: Oct 2008
Posts: 103
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^Maybe testing/swapping the injectors is the next step. Did you get this resolved?
I got the dreaded misfire codes this week on the way to work. I was just idling in traffic and the car started chugging out of nowhere and sounded like crap. The CEL was flashing and it would barely accelerate past 35 mph. Pulled the codes and got P1399, P0300, P0302 and P0303.
At 98K miles I figured needed to do the spark plugs anyway, so i swapped them out and they looked terrible. There was basically no tip left.
I reset the CEL and the car drives great now, no more codes, such a relief. It actually feels much smoother than before.
Good luck to any others out there with a misfire.
I got the dreaded misfire codes this week on the way to work. I was just idling in traffic and the car started chugging out of nowhere and sounded like crap. The CEL was flashing and it would barely accelerate past 35 mph. Pulled the codes and got P1399, P0300, P0302 and P0303.
At 98K miles I figured needed to do the spark plugs anyway, so i swapped them out and they looked terrible. There was basically no tip left.
I reset the CEL and the car drives great now, no more codes, such a relief. It actually feels much smoother than before.
Good luck to any others out there with a misfire.
Registered User
Joined: Apr 2011
Posts: 50
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From: Birmingham, AL
I cranked up the car to leave work and I see the CEL come on. I pull the codes and this is what it is throwing:
P0301 - Misfire cyl #1
P0302 - Misfire cyl #2
P0300 - Random/multiple misfire
So, I ran a compression check and here are my results:
Cyl #1: 235
Cyl #2: 225
Cyl #3: 265
Cyl #4: 260
It looks like cyl #1 and #2 are low compared to the others, and these happen to be the ones misfiring. I took a look at the spark plugs and the electrodes look rounded to me, so I replaced them. The car idles noticeably smoother now. I cleared the misfire code, and so far I've driven around 350 miles without the light coming back on.
I'm thinking the misfire may have occurred due to insufficient current to the coils and the bad spark plugs weren't helping. I notice when I first crank the car up, my dash will flicker a little bit as the car is idling. I remember the check engine light came on after the car had been sitting for a few hours (cold engine) and I let it idle with the AC on high. My battery may be getting close to croaking, and as far as I know, it's still the original factory battery.
In any case, I'm still going to do a valve adjustment since the compression check wasn't flawless. Do you guys think it was just a coincidence the misfire happened on the two cylinders that have low compression (assuming low current is the cause)? That's the thing that has me worried.
P0301 - Misfire cyl #1
P0302 - Misfire cyl #2
P0300 - Random/multiple misfire
So, I ran a compression check and here are my results:
Cyl #1: 235
Cyl #2: 225
Cyl #3: 265
Cyl #4: 260
It looks like cyl #1 and #2 are low compared to the others, and these happen to be the ones misfiring. I took a look at the spark plugs and the electrodes look rounded to me, so I replaced them. The car idles noticeably smoother now. I cleared the misfire code, and so far I've driven around 350 miles without the light coming back on.
I'm thinking the misfire may have occurred due to insufficient current to the coils and the bad spark plugs weren't helping. I notice when I first crank the car up, my dash will flicker a little bit as the car is idling. I remember the check engine light came on after the car had been sitting for a few hours (cold engine) and I let it idle with the AC on high. My battery may be getting close to croaking, and as far as I know, it's still the original factory battery.
In any case, I'm still going to do a valve adjustment since the compression check wasn't flawless. Do you guys think it was just a coincidence the misfire happened on the two cylinders that have low compression (assuming low current is the cause)? That's the thing that has me worried.
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Joined: Jun 2004
Posts: 11,315
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From: Tulsa, Oklahoma USA
I notice when I first crank the car up, my dash will flicker a little bit as the car is idling. I remember the check engine light came on after the car had been sitting for a few hours (cold engine) and I let it idle with the AC on high. My battery may be getting close to croaking, and as far as I know, it's still the original factory battery.
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Joined: Apr 2011
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From: Birmingham, AL
Originally Posted by Fearnight' timestamp='1306165058' post='20605255
I notice when I first crank the car up, my dash will flicker a little bit as the car is idling. I remember the check engine light came on after the car had been sitting for a few hours (cold engine) and I let it idle with the AC on high. My battery may be getting close to croaking, and as far as I know, it's still the original factory battery.
edit: Looks like the dash flickering is definitely the alternator
https://www.s2ki.com/s2000/topic/753...#entry17788330
http://s2000.com/forums/engine-tech-...lternator.html
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Joined: Apr 2011
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From my journey in trying to find out why i get hesittion or bucking in low rpm seems to be the connection from the TPS and the engine wire harness. If you wiggle the harness around, the engine definately sounds rough. I wired the 3 wires directly to the TPS and now the problem of the car hesitating/bucking has gone away. Kind of like the MAP whack mod, but for the TPS. Just something you guys might want to take a look at. Now I have to hunt for the mysterious misfire problem.
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Joined: Jan 2007
Posts: 1,402
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I'm posting on this because I searched, and this is the thread on the FAQ thread regarding misfires.
A good way to troubleshoot your coils:
One by one, while your car is running, pull your coils out. I had a #3 cylinder misfire, so I pulled #3 out first. No change. I put it back on and pulled #1, my car almost died, it was running like crap. Same thing with #2 and #4. Diagnosis, #3 is likely having a spark issue. I had JUST changed the plugs with the OEM NGK Iridium plugs, all the old ones looked exactly the same.
My new problem is two-fold. I spent my disposable money on spark plugs, fuel system cleaner, a crazy night at the bars, and a new hat. The autopart stores here only sell coils in sets of 4, and want $100 that I can't spend. So I might have to wait until the 15th, but that's not too long.
A good way to troubleshoot your coils:
One by one, while your car is running, pull your coils out. I had a #3 cylinder misfire, so I pulled #3 out first. No change. I put it back on and pulled #1, my car almost died, it was running like crap. Same thing with #2 and #4. Diagnosis, #3 is likely having a spark issue. I had JUST changed the plugs with the OEM NGK Iridium plugs, all the old ones looked exactly the same.
My new problem is two-fold. I spent my disposable money on spark plugs, fuel system cleaner, a crazy night at the bars, and a new hat. The autopart stores here only sell coils in sets of 4, and want $100 that I can't spend. So I might have to wait until the 15th, but that's not too long.
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Joined: Nov 2009
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All this information was very helpful. My S2K started misfiring and the check engine light went on and I first assumed it was water in my gas. I put dry gas in and went through 2 tanks of gas but no changes. The next thing I did was put in Lucas injector cleaner which didnt fix the misfire. I replaced the plugs, the CEL went off and the engine ran much smoother but there was still slight misfire. Finally I bought new coils off ebay and my S2K if finally running like a champ! Thanks for all the information... you all saved me time and money.
Joined: Mar 2011
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Originally Posted by FilthPig,Jul 27 2010, 07:48 PM
Okay maybe a couple things someone can advise and clear up for me. Maybe it's wishful thinking but I'm having a hard time correlating a bent valve other valve problem and a intermitent rough idle.....which seems to be associated with my CEL misfire codes.
It seems like this would more likely be caused by the injectors, coils, spark plugs or possibly that map whack thing and other things on this list I read.
I'm still torn beteween troubleshooting this further myself versus just taking it into the dealership. The car is still under warranty but just barley, 53k miles. So it seems to me that I'd want to at least take it to the dealership so that the issue is brought to their attention before the warranty expires. Any thoughts.... anybody??
Bent valves or some other valve problem is scary...it's never been over revved so I don't see this as the possible cause. I do "rail it" on a regualr basis like S2ooonvegas mentions...I'm not just putting my S2000 around. And I have run into the rev limter on occasion....who hasn't... but not hard so that should give an over rev. Never miss shifts or downshift too hard.
It seems like this would more likely be caused by the injectors, coils, spark plugs or possibly that map whack thing and other things on this list I read.
I'm still torn beteween troubleshooting this further myself versus just taking it into the dealership. The car is still under warranty but just barley, 53k miles. So it seems to me that I'd want to at least take it to the dealership so that the issue is brought to their attention before the warranty expires. Any thoughts.... anybody??
Bent valves or some other valve problem is scary...it's never been over revved so I don't see this as the possible cause. I do "rail it" on a regualr basis like S2ooonvegas mentions...I'm not just putting my S2000 around. And I have run into the rev limter on occasion....who hasn't... but not hard so that should give an over rev. Never miss shifts or downshift too hard.
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