Misfire codes, but can't feel a misfire
08-05-2016, 05:47 PM
#1
Thread Starter
Join Date: Aug 2016
Location: Pennsylvania
Posts: 3
Misfire codes, but can't feel a misfire
So my 2004 GT (4.6 v8, 5 speed manual) is sending multiple misfire codes (P0300, P0302, P0304, P0306, P0307, P0308) but I don't feel any misses anywhere. I sometimes feel a hint of studder at idle but its not much. It pulls hard and runs great. The idle does hang high for a few seconds between shifts tho. I don't know what the issue could be. It starts right up but sometimes takes a little longer to start. I'm wondering if it might not be getting enough fuel (clogged fuel filter or something). The other day when the light was on (before I knew the codes) I ran it thru the gears kinda hard and the service engine soon light went from solid to flashing then when I let off a few seconds later, it went back to solid. Any ideas? It has high flow cats and mufflers on it and an x-pipe. I am unaware of any other mods done (was a recent purchase). Thanks
08-05-2016, 07:26 PM
#2
4th Gear Member
Join Date: Nov 2009
Location: SoCal
Posts: 1,826
http://www.obd-codes.com/p0300
In my experience and observation, most misfire symptoms are ignition related as opposed to fuel delivery etc. Being that the car is new to you I would start with the basics - plan on replacing plugs and inspect the rubber boots on the coils for any signs of deterioration or cracking, replace boots if necessary.
The flashing CEL is indicative of a misfire event occurring in real time.
For plugs, I use and recommend Autolite 764 (regular copper). You can buy all 8 for around $12. There is no benefit to platinum besides a longer service life - platinum plugs are usually good to 50 or 60K, copper usually to 30 or 40K. I definitely would not spend the extra money for iridium or fancy multi-electrode plugs with advertising hype that promises 10 hp or 10% better fuel economy - it's all BS anyway and many people who have used them in these cars report that their engine doesn't seem to like them.
New fuel filter is a good idea as well since you don't know how old your current one is. About $15 and as many minutes of your time to replace.
And for $6 get a can of MAF cleaner and use it (they make a special purpose spray for this, use absolutely nothing else).
Do those things, reset the PCM, let us know what happens.
In my experience and observation, most misfire symptoms are ignition related as opposed to fuel delivery etc. Being that the car is new to you I would start with the basics - plan on replacing plugs and inspect the rubber boots on the coils for any signs of deterioration or cracking, replace boots if necessary.
The flashing CEL is indicative of a misfire event occurring in real time.
For plugs, I use and recommend Autolite 764 (regular copper). You can buy all 8 for around $12. There is no benefit to platinum besides a longer service life - platinum plugs are usually good to 50 or 60K, copper usually to 30 or 40K. I definitely would not spend the extra money for iridium or fancy multi-electrode plugs with advertising hype that promises 10 hp or 10% better fuel economy - it's all BS anyway and many people who have used them in these cars report that their engine doesn't seem to like them.
New fuel filter is a good idea as well since you don't know how old your current one is. About $15 and as many minutes of your time to replace.
And for $6 get a can of MAF cleaner and use it (they make a special purpose spray for this, use absolutely nothing else).
Do those things, reset the PCM, let us know what happens.
08-05-2016, 07:50 PM
#3
Thread Starter
Join Date: Aug 2016
Location: Pennsylvania
Posts: 3
http://www.obd-codes.com/p0300
In my experience and observation, most misfire symptoms are ignition related as opposed to fuel delivery etc. Being that the car is new to you I would start with the basics - plan on replacing plugs and inspect the rubber boots on the coils for any signs of deterioration or cracking, replace boots if necessary.
The flashing CEL is indicative of a misfire event occurring in real time.
For plugs, I use and recommend Autolite 764 (regular copper). You can buy all 8 for around $12. There is no benefit to platinum besides a longer service life - platinum plugs are usually good to 50 or 60K, copper usually to 30 or 40K. I definitely would not spend the extra money for iridium or fancy multi-electrode plugs with advertising hype that promises 10 hp or 10% better fuel economy - it's all BS anyway and many people who have used them in these cars report that their engine doesn't seem to like them.
New fuel filter is a good idea as well since you don't know how old your current one is. About $15 and as many minutes of your time to replace.
And for $6 get a can of MAF cleaner and use it (they make a special purpose spray for this, use absolutely nothing else).
Do those things, reset the PCM, let us know what happens.
In my experience and observation, most misfire symptoms are ignition related as opposed to fuel delivery etc. Being that the car is new to you I would start with the basics - plan on replacing plugs and inspect the rubber boots on the coils for any signs of deterioration or cracking, replace boots if necessary.
The flashing CEL is indicative of a misfire event occurring in real time.
For plugs, I use and recommend Autolite 764 (regular copper). You can buy all 8 for around $12. There is no benefit to platinum besides a longer service life - platinum plugs are usually good to 50 or 60K, copper usually to 30 or 40K. I definitely would not spend the extra money for iridium or fancy multi-electrode plugs with advertising hype that promises 10 hp or 10% better fuel economy - it's all BS anyway and many people who have used them in these cars report that their engine doesn't seem to like them.
New fuel filter is a good idea as well since you don't know how old your current one is. About $15 and as many minutes of your time to replace.
And for $6 get a can of MAF cleaner and use it (they make a special purpose spray for this, use absolutely nothing else).
Do those things, reset the PCM, let us know what happens.
08-06-2016, 12:24 PM
#5
Resident Ford Troll
Join Date: Jul 2006
Location: Delaware
Posts: 6,717
before you start throwing parts at it, you need to check fuel pressure and monitor fuel trims. You either have a supply issue or possibly a vacuum leak... bad intake gaskets arent uncommon
of course worn spark plugs/faulty coils can all cause misfires...but to be slight and that many holes at once, i feel like its fuel or air leak
of course worn spark plugs/faulty coils can all cause misfires...but to be slight and that many holes at once, i feel like its fuel or air leak
08-14-2016, 06:55 PM
#6
Thread Starter
Join Date: Aug 2016
Location: Pennsylvania
Posts: 3
Well, I changed the fuel filter (used a Motorcraft), changed the plugs (motorcraft), and coils. Also bought some MAF cleaner and cleaned the MAF sensor and ran a full tank of gas thru it that had injector cleaner added to it. I put about 70 miles on it (after disconnecting the battery) then the check engine light came on 
I got the codes read and I had P0300, P0304, and P0306. Last time I drove it twice after the light came on, where as this time I went right to get it read. I'm wondering if more codes would have shown up if I had driven it a little longer like last time. It still has a slight pop every now and then on idle and it feels like a slight stumble. I can run it on 5th gear at 40mph and its smooth and it pulls strong. All the plugs that came out looked like it is running lean. I don't have a scanner or anything to check what the fuel pressure is reading. I'm starting to wonder if there is a tune in it that I don't know of and it is causing issues
I got the codes read and I had P0300, P0304, and P0306. Last time I drove it twice after the light came on, where as this time I went right to get it read. I'm wondering if more codes would have shown up if I had driven it a little longer like last time. It still has a slight pop every now and then on idle and it feels like a slight stumble. I can run it on 5th gear at 40mph and its smooth and it pulls strong. All the plugs that came out looked like it is running lean. I don't have a scanner or anything to check what the fuel pressure is reading. I'm starting to wonder if there is a tune in it that I don't know of and it is causing issues
08-17-2016, 11:26 PM
#7
Resident Ford Troll
Join Date: Jul 2006
Location: Delaware
Posts: 6,717
id still be willing to bet you have a vacuum leak
surprised you dont have any p0171/174 codes.. but it appears to be a fuel mixture/delivery issue.. you could of used that money spent on parts to pay a shop to fix whats actually wrong with it lol
surprised you dont have any p0171/174 codes.. but it appears to be a fuel mixture/delivery issue.. you could of used that money spent on parts to pay a shop to fix whats actually wrong with it lol
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