no one has had a misfire code that wasn't resolved by new plugs/swapped coils? Open to ideas...

 

Maybe the ignition is putting enough spark to the coil at such a high rate... or it might have a bad or loose connection to the coil. I would check all the wires to see if maybe something might be cut, burnt or anything out of the normal range.

 

Hey guys,

I'm still struggling with this code. I've checked the wiring and everything looks like new. I swapped coils around and reset and the code still returns for cylinder 1. I'm on a new tank of gas now with fuel injector cleaner - still the problem persists.

I can run the engine at any rpm, maintain 45 mph in 2nd gear for 15 seconds, no problem will not trip the check engine. The check engine light is entirely dependent on road speed. Cross ~80 and the check engine light comes on - misfire #1 P0301. I'm baffled! The speed threshold of 80-85 somehow is causing that light to turn on. What can it possibly be? The engine runs great all the time. The only possible thing I can think of is the AWR tranny mount causing more vibration at those speeds and somehow it interprets that as a misfire on #1... but that's pretty far out there. I may throw the stock mount back in just to see though at this point.

 

I would check for vacuum leaks. I had leak between my TB and IM when I first put the spacer on, and it would sometimes cause this. Also, try holding the RPM at 3.5k in a lower gear at a lower speed and see if that triggers anything.

 

general procedure for finding missfire.

1st swap plug to next cyl (i know you put new ones in but do it anyway)

then swap coil to 3rd cyl.

test.

if it doesnt move, then swap injector to another cyl.

test.

still doesnt move, check wiring to coil and injectors.

leak test intake a lean cyl can cause a missfire.

if no leak is found, procede to check cyl integrety compression, and leak down test.

it is possible that you have a defective plug, not sure if you swaped that with another yet.

 

QUOTE (90turbo1 @ Feb 20 2009, 01:16 AM) index.php?act=findpost&pid=1522420

general procedure for finding missfire.

1st swap plug to next cyl (i know you put new ones in but do it anyway)

then swap coil to 3rd cyl.

test.

if it doesnt move, then swap injector to another cyl.

test.

still doesnt move, check wiring to coil and injectors.

leak test intake a lean cyl can cause a missfire.

if no leak is found, procede to check cyl integrety compression, and leak down test.

it is possible that you have a defective plug, not sure if you swaped that with another yet.[/b]

+1 if the coil itself proves out to be good, I'd suspect a tiny clog in the injector.

 

I had that problem for a while. I guess it could be because of the NGK's... I had G-power in it and it misses like crazy... I swap coils and it still... I than swicth to NGK IX and gap them to .45 and it went away.

 

wow thats a toughie! i just reiterate what other people said:

1. vacuum leak (i doubt this because it would cause p0300)
2. spark plug gaps (check em!)
3. there's always the slim chance you put another defective plug in..

id switch the coils again to confirm

but my guess is its electrical, which is hard to find. thats such a strange problem! please keep us updated, this is very strange.

 

I haven't had time to dive back into it. I'm rebuilding an engine - diff car - and that has all my attention right now. I agree that I think it's electrical gremlin. For now I keep it under 85 and have no light. On occassion I sneak over that speed I need the obdii reader handy to clear it. That will have to do for now. I don't anticipate having time for it till next month. I thank all of you for your replies. I'll update when I get to the bottom of it.

QUOTE (hot6onaplatter @ Feb 25 2009, 11:03 PM) index.php?act=findpost&pid=1525287

wow thats a toughie! i just reiterate what other people said:

1. vacuum leak (i doubt this because it would cause p0300)
2. spark plug gaps (check em!)
3. there's always the slim chance you put another defective plug in..

id switch the coils again to confirm

but my guess is its electrical, which is hard to find. thats such a strange problem! please keep us updated, this is very strange.[/b]

I haven't had time to dive back into it. I'm rebuilding an engine - diff car - and that has all my attention right now. I agree that I think it's electrical gremlin. For now I keep it under 85 and have no light. On occassion I sneak over that speed I need the obdii reader handy to clear it. That will have to do for now. I don't anticipate having time for it till next month. I thank all of you for your replies. I'll update when I get to the bottom of it.

QUOTE (hot6onaplatter @ Feb 25 2009, 11:03 PM) index.php?act=findpost&pid=1525287

wow thats a toughie! i just reiterate what other people said:

1. vacuum leak (i doubt this because it would cause p0300)
2. spark plug gaps (check em!)
3. there's always the slim chance you put another defective plug in..

id switch the coils again to confirm

but my guess is its electrical, which is hard to find. thats such a strange problem! please keep us updated, this is very strange.[/b]

 

sounds good. damn gremlins!

 

QUOTE (6GT @ Feb 25 2009, 11:33 PM) index.php?act=findpost&pid=1525260

I had that problem for a while. I guess it could be because of the NGK's... I had G-power in it and it misses like crazy... I swap coils and it still... I than swicth to NGK IX and gap them to .45 and it went away.[/b]

You are probably thinking of the gapping for the Pulstars. The gapping should be between .051-.057 for our V6 on a mostly stock setup per the owner's manual. You can probably gap a little more if you are using stronger COPs like Sniper or WeaponX. The NGK IXs typically come pregapped at .052 and recommend that gapping for our car. I'd leave the gapping at that. If you already closed the gap, I would open it back up to the .051-.057 range. But I wouldn't recommend closing the gap below that, you'll only risk losing some power and poorer gas mileage.

Paul

 

QUOTE (VirtualMirage @ Feb 27 2009, 07:38 AM) index.php?act=findpost&pid=1525985

You are probably thinking of the gapping for the Pulstars. The gapping should be between .051-.057 for our V6 on a mostly stock setup per the owner's manual. You can probably gap a little more if you are using stronger COPs like Sniper or WeaponX. The NGK IXs typically come pregapped at .052 and recommend that gapping for our car. I'd leave the gapping at that. If you already closed the gap, I would open it back up to the .051-.057 range. But I wouldn't recommend closing the gap below that, you'll only risk losing some power and poorer gas mileage.

Paul[/b]

I left them at the regualar gap & my car was idle rough... So I went higher and it seem to mis in the high end.. So I gap lower untill the mis went away. Well after so many sparks plug changes, I can changes them in like 20 mins top now. ahah

 

QUOTE (6GT @ Feb 27 2009, 10:58 AM) index.php?act=findpost&pid=1526026

I left them at the regualar gap & my car was idle rough... So I went higher and it seem to mis in the high end.. So I gap lower untill the mis went away. Well after so many sparks plug changes, I can changes them in like 20 mins top now. ahah[/b]

If you were having rough idle at stock gap and misfires at higher gap, then I would be concerned about your COPs or somewhere else in your ignition system.

Paul

 

QUOTE (VirtualMirage @ Feb 27 2009, 12:48 PM) index.php?act=findpost&pid=1526211

If you were having rough idle at stock gap and misfires at higher gap, then I would be concerned about your COPs or somewhere else in your ignition system.

Paul[/b]

It was the spark plugs.... I talk to O 'Reilly about it and they said that the box of NGK was drop while reciving. So that was the problem...

 

Oh, ok. At least there was a reason behind it.

 

what should the gap be on pulsars? i just checked my misfiring cylinder and the plug was burnt out and at 65 lol

 

Update:

Finally had some time to look back into this. I replaced all 6 coils with BRAND NEW Motorcraft coils. I took a look at the plugs while I had the intake manifold off. They look really good - perfect even.

So 6 new coils, perfect plugs with less than 2k on them and sure enough come 85 mph check engine light comes on, push it past 85 and it'll flash indicating a serious misfire. Still P0301.

I am so frustrated at this seemingly unsolvable problem. I've established that its not the plugs, not the coils and the wiring on the coils looks perfect. Only thing left is a bad injector on #1 or a faulty ecm. What is so strange is that it seems to have nothing to do with engine RPM but rather road speed. Though, if I am accelerating hard though I can whiz right past 85 and no CEL. Ease up or coast and it'll pop right on.

What can this be if not coils/plugs? It runs perfect throughout the whole ordeal - if not for the CEL I would never suspect there to be anything wrong. I'd hate to replace the injector and still have the light come on. I don't want to throw more parts at it in hopes of resolving the issue. Has anyone had this happen??

 

According to the service manual, it could be a bunch of things. It could be the spark plugs, ignition coils, fuel injector, air leak between plenum and intake manifold or intake and cylinder head, low engine compression, bad electrical connection or PCM. It says you can swap the injector with another one. It also says you need a special tool to remove a plastic fuel hose that the injectors are in line with.

 

QUOTE (chilimax21 @ Mar 31 2009, 07:36 PM) index.php?act=findpost&pid=1541049

According to the service manual, it could be a bunch of things. It could be the spark plugs, ignition coils, fuel injector, air leak between plenum and intake manifold or intake and cylinder head, low engine compression, bad electrical connection or PCM. It says you can swap the injector with another one. It also says you need a special tool to remove a plastic fuel hose that the injectors are in line with.[/b]

Excellent idea on swapping the injectors. I'm going to try that and if the misfire jumps to a different cylinder then I know for sure it is the injector. I'm familiar with GM injectors which are easy to remove from the fuel rail, just a metal clip and an o-ring. I'll have to take a look at the ones on the mazda and see how they are secured.

I have a friend who is going through a very similar situation with an 04 RX8.

 

QUOTE (jm6s @ Mar 31 2009, 11:16 PM) index.php?act=findpost&pid=1541070

Excellent idea on swapping the injectors. I'm going to try that and if the misfire jumps to a different cylinder then I know for sure it is the injector. I'm familiar with GM injectors which are easy to remove from the fuel rail, just a metal clip and an o-ring. I'll have to take a look at the ones on the mazda and see how they are secured.

I have a friend who is going through a very similar situation with an 04 RX8.[/b]

Have you checked the Crank position sensor? did you install the new Fluid dampr crank pulley?

I had a misfire problem for months till I finally cranked down on the crank pulley... only moved a fraction of an inch but have been misfire free ever since.
I do have the Fluid Dampr... but you never know maybe the stock one loosened a bit.
I had the same symptoms... cruising speed misfire CEL! Also check into the the crank sensor and i think the cam position sensor can cause misfires as weel

 

QUOTE (rkeytek @ Apr 1 2009, 06:58 AM) index.php?act=findpost&pid=1541175

Have you checked the Crank position sensor? did you install the new Fluid dampr crank pulley?

I had a misfire problem for months till I finally cranked down on the crank pulley... only moved a fraction of an inch but have been misfire free ever since.
I do have the Fluid Dampr... but you never know maybe the stock one loosened a bit.
I had the same symptoms... cruising speed misfire CEL! Also check into the the crank sensor and i think the cam position sensor can cause misfires as weel[/b]

The pulley is original and has never been touched so I imagine that can't be to blame considering how tight those things are on there. If someone has the torque spec I can check it just to be sure. At this point I am really hoping it is the fuel injector as that would be a quick/easy and more importantly cheap fix! I feel like I won't be that lucky though.

 

make sure the intake manifold gasket is in place and not messed up

 

QUOTE (jm6s @ Mar 31 2009, 05:33 PM) index.php?act=findpost&pid=1540897

Update:

Finally had some time to look back into this. I replaced all 6 coils with BRAND NEW Motorcraft coils. I took a look at the plugs while I had the intake manifold off. They look really good - perfect even.

So 6 new coils, perfect plugs with less than 2k on them and sure enough come 85 mph check engine light comes on, push it past 85 and it'll flash indicating a serious misfire. Still P0301.

I am so frustrated at this seemingly unsolvable problem. I've established that its not the plugs, not the coils and the wiring on the coils looks perfect. Only thing left is a bad injector on #1 or a faulty ecm. What is so strange is that it seems to have nothing to do with engine RPM but rather road speed. Though, if I am accelerating hard though I can whiz right past 85 and no CEL. Ease up or coast and it'll pop right on.

What can this be if not coils/plugs? It runs perfect throughout the whole ordeal - if not for the CEL I would never suspect there to be anything wrong. I'd hate to replace the injector and still have the light come on. I don't want to throw more parts at it in hopes of resolving the issue. Has anyone had this happen??[/b]

COP's are fairly predictable. Like a light switch - either it works or it don't. Before you go nuckin futz I'd swap 1 to 2 and vice versa. If you still throw a code, I would suspect the loom. Just a hunch from way to many years of chasing gremlins on COP cars. I know this sound nutz - grab the loom and give it a good yank and see what happens. Yes it's a stretch but trust me BTDT w/ freakin coils.

 

I swapped each fuel injectors to a different location. I checked all the wiring/loom on the injectors and coils - all appears ok.

So with each injector in a different spot.... still the same damn code! P0301, misfire on #1. So at this point I've replaced just about everything it could be including coils/plugs/injectors. And yes the manifold gaskets appear ok and are seated correctly.

I'm out of ideas. I don't want to bring it to a dealer because they are going to go down the same path as me and tell me first I have a bad coil pack, charge a fortune to replace it, realize it isn't the problem and then continue to throw parts at it all the while running up the bill and claiming each of these parts was bad. Any other ideas? It really doesn't appear to be a wiring issue. Can the computer itself be bad? I'd hate to keep throwing parts at it but I really don't know what to do. Can I get the computer reflashes? Would any dealer do this, and how much could I expect to be charged? Keep in mind the engine runs perfect through all of this.

 

if the car runs fine i wouldn't worry about it. if it starts shaking or having loss of power i would, but honestly is it worth it throwing time and money at a such a mysterious problem? not if the car drives fine in my mind.

I'd just be curious to know what the the hell it is! ECU is my best guess but geez thats a toughie