I had a misfire in my cyl #6 about 3 weeks ago, I thought it was strange, because that was one of the 2 coils in my car that were the updated (grey dot) ones. So I bought a new coil and put it in the #6 cyl spot, and moved the supposedly bad grey dot coil to the #2 cyl. --> car was running great for about 2 weeks, then over the past few days I have felt it periodically misfire, gradually getting worse. finally today my check engine light comes on, so I hook up my OBDII, and CYL #6 MISFIRE??????

And the original grey dot coil in #6 that is now in cyl #2 is working fine???

 

Are you getting code P1320 along with P0306? That would for sure be the coil, but if you are getting it alone I would start with maybe the spark plug. If your 6 cylinder was misfiring, it may be the plug got messed up. Either way its probably the cheapest fix. If you have a multi meter put it to this test and let us know what the results are. Ignition coil test linky.

Fat

 

I checked the plug, its a 6 month old Platinum Denso and it was fine.
I was gonna do the coil test with my multi meter, but I have read some inconclusive results from that test, not to mention I am pretty sure the coil is fine.
I'm thinking either the ECM or the plug that attaches to the coil, or maybe the wire??? thats why I am asking to see if anyone has had this problem.

 

I wonder if the ECM update would help this???

 

I would still replace the plug first. A simple test you can do is move that plug only to another cylinder and replace it with that other one. If the misfire follows the plug than that caused the problem, if it stays then look at the coil, coil connectors. Btw, are you using the right grade of fuel?

 

I'll try the plug change, what is the gap supposed to be?

and as far as the fuel, there is 92 in there right now, which is funney because I have been trying to see which I get better MPG with reg or super, so I ran two tanks of reg, and this is my 1st tank of super, and it seems the misfire got worse with the super?????

 

It may have been the regular gas you had in there that caused the misfire

 

Gap it to .044"

Fat

 

regular gas does not misfire. It fires too easily. We know the injector is okay, or is that a different code?

 

injector is a different code, I just switched the plug over to the #4 cyl, and it's still misfiring,
As far as the fuel grade, it has super in it now, and the super appears to be making it misfire worse???

So what I am almost positive it's not:
-Coil
-Plug

 

Also getting the following codes:
p0420 o2 sensor
p0430 o2 sensor
p0135 02 sensor
H025 Heater someting

 

P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
P0430 - Catalyst System Efficiency Below Threshold (Bank 2)
P0135 - Front O2 Sensor Heater (Bank 1)

Could these codes be from the unburned fuel from the misfire?

 

I assume that your #6 is misfiring, sounds like a coil.

It could be that your pre-cat and main cat are showing because of unburnt fuel from #6 so I would go with the coil first. How long ago did you replace it and was it an updated coil you replaced it with?

As for O2 heater problem it is likely sensor heater gone bad, though I would reset the computer after coil replacement and may be it will go away, otherwise, you'll need to replace it...

 

all three coils in the front are updated and new, and #6 is about two weeks old. And just to make sure it wasnt the coil, I switched them around and it is still doing it,
I also just chaged all three plugs in the front, and added a whole lot of dielectric grease....
Then took it for a drive, and its still puttering when i slow to a stop. the "Check Engine Light" came back on, but not with a misfire, just with the P0135: HO2S Heater performance Bank 1 Sensor 1
so far, but I am pretty sure that after a day or two the misfire code will be there again, I can feel it....

 

IMO, I would replace the sensor first as it is your primary O2 (controls fuel trim)... After that you might be OK... I would wait for the misfire code if it shows up again to go further with coil/plug investigations...

 

you think that code is def the sensor needing to be replaced, and not just the excess unburned fuel?

 

If that was the problem then you would have got a different code (for signal). This code is for heater, indendent of signal. Heater brings up the sensor to its operating temp and if the heater mulfunctions then it could mess up the signal (due to improper reading as a result of wrong temp on the sensor filament)...

 

cool, what about if I put in one of those O2 simulators, will that cause my fuel trim to still be off?

 

1. Simulator won't work as it only simulates the signal not the heater

2. You could simulate the heater by using a resistor. Go to o2sim.com and there you can find the requirements for replacement/simulations of a heater.

3. You should not replace a primary (front) O2 sensor with a simulator as it controls your fuel trim and it will likely not work even if you tried...

4. Hope this helps

 

Yes it did,
It's funney the misfire happens almost consistently at 1800rpms & when I come to a stop at a light or stop sign.

 

Ok just read my MIL light again, and I got the P0306 Cyl #6 misfire back
along with the P0420 and the P0135
So even if I replace that o2 sensor, it still isn't going to fix this misfire in CYL 6, which isn't the coil or the plug (positive now)
HELP!!!!!!!!!!!!!!!!!!!!!!!

 

I would first fix the oxygen sensor problem. Then look at the cat's if the SES comes back on...

 

but what do the cats have to do with the #6 cyl misfiring?

I am going to replace the O2 sensor, but my car is still driving me nuts with this misfire........

 

You may have an intake manifold leak, which in turn causes a lean condition, which in turn causes your ECU to over compensate on fuel and fouls the #6 plug. This is also probably killing your catalytic converters by letting in too much raw fuel.

 

Except that I switched the plug yesterday TWICE and it is still doing it, so the plug is not getting fouled.

 

did you have any work done to the car not long before you got a misfire? If yes, something could be installed improperly.

 

nope, I put a pop charger intake in, but it was misfiring prior to that

 

SR20DEN brought up a good point. Check your intake set up even though you had misfire before it. Make sure there are no air leaks after MAF. One way to test this out is to take off your pop-charger filter and cover (seal) the hole going to the MAF. If your car stalls than there are no leaks in intake and your problem lies elsewhere, if the car does not stall then you have an intake air leak...

 

ok, I am going to check that now.
What about the injector? is there a way to check that?

 

To check an injector is a little more PITA. Ways of checking them that I know of are: possibly by using a Consult II or another scanner that can monitor individual injector operation, or if you pull out the injector from that cylinder, disconnect the coil, turn the key on but without starting the car and see if the injector leaks during fuel prime. Otherwise, I don't know how you can check visually if it is over/under spraying while the car runs... Another thing to consider is that your MAF may be misreporting the air volume coming in, but that may be somewhat of a long shot... Also check your vacuum lines for leaks...

 

just changed the MAF, it was the first thing I changed when I felt the misfire.

 

OK... Is the pipe between MAF and TB sitting OK? Checked the vacuum lines?

 

yes I did check that all, and it is sitting ok, the only hose that looks funney is the one that was connected to my air duct box that I took out with the main air box.
But all in all, could a vaccum line really be causing just cylinder #6 to be misfiring? woulding it cause others to also?

 

does anyone know how to check the wire harness that hooks up to the coils?

 

???????????????????????????

 

At your own risk: one way to do it is get a spare good plug, take out the coil that is suspect and keep it connected to the harness, put the plug into it, put the plug against a good engine ground, disconnect the fuel injector from that cylinder, start the car and watch for sparks coming out of the plug or side of the coil. If there are no sparks at the plug end, then either the wiring or the coil is bad. Also watch for sparks if any are coming from anywhere else - that is not a good thing either...

I'll take a look into the service manual tomorrow and will let you know if I find anything on the wiring verification...

 

"I'll take a look into the service manual tomorrow and will let you know if I find anything on the wiring verification..."

Yeah that would be great, I am not to crazy about the other idea, I would rather hook a multi meter up to the plug, I just need to know which contacts to hook it up to,a nd what to look for.

 

I checked the manual and it only references the spark test I mentioned.

Here is a check list of possible causes for misfire (you may not need to follow the order):
1. Spark plug or coil fault - tests I mentioned
2. Insufficient cylinder compression - do a compression test
3. Fuel pressure - check regulator, filter, fuel lines
4. Injectors - clogged, leaking, mulfunctioning (visual, Consult II)
5. Intake air leak - check vacuum, intake hoses, post-MAF, etc.
6. Flywheel - not likely but to consider
7. O2 sensor - I think yours was throwing the code for it
8. Clogged pre-cats or main cat
9. MAF

This should give you some idea where to look at...

 

Thank you very much for the info, I am leaning toward #4, and since I don't have a compression gauge, I think it may have to go over to my mechanics.
are the injectors easy to take out?

 

You are welcome Let us know what you find and how it goes...