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Random Cylinder Misfire

Cduncan133

Member
Joined
February 12, 2015
Messages
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City, State
Fort Wayne, Indiana
Year, Model & Trim Level
2004 Ford Explorer
Got a CEL code for a P0300. The explorer has had some random hesitations/stumbles the last month so I knew something was going to come up. CEL came on as I started to accelerate pretty hard. It even blinked for a few seconds before turning solid.

The spark plugs are recent, only 3 months old. Everything else, I'm not sure.

Where would I start? Is there any way to test my ignition coils and fuel injectors?

If it helps, I did start getting a buzzing noise while accelerating this week. It's almost the same buzz the power steering pump makes when it's low on oil, or cold started in low to below freezing temps (well, at least mine does that). I haven't seen any noticeable losses in fuel economy either.

Thanks!
 



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Got a CEL code for a P0300. The explorer has had some random hesitations/stumbles the last month so I knew something was going to come up. CEL came on as I started to accelerate pretty hard. It even blinked for a few seconds before turning solid.

The spark plugs are recent, only 3 months old. Everything else, I'm not sure.

Where would I start? Is there any way to test my ignition coils and fuel injectors?

If it helps, I did start getting a buzzing noise while accelerating this week. It's almost the same buzz the power steering pump makes when it's low on oil, or cold started in low to below freezing temps (well, at least mine does that). I haven't seen any noticeable losses in fuel economy either.

Thanks!

I'm sure you are over the "100,000" mile mark, you most likely are going to need new ignition coil's, on my 04' 4.6 I got a cylinder 8 misfire, explorer was stumbling and shaking at red lights (with a blinking CEL light which scared the living crap out of me) so went to investigate and about 1oz of water covering the spark inside the hole which led to the misfire, the coils were absolutely disgusting! full of dirt and crap from over the years (125k miles) so I cleaned them up and changed my plugs (NGK or oem Motorcraft will do just fine) if you have a different plug the explorer may not like them, just like my lexus suv wanted to **** out the bosch plugs I had put in (big no no) it was having random misfires like nuts! went back to oem and tada! Problem fixed, so depending on mileage, vehicle use and brand/type of plugs you are running plugs and or coils might be dieing! good luck hope this helps ya! :D
 






I'm sure you are over the "100,000" mile mark, you most likely are going to need new ignition coil's, on my 04' 4.6 I got a cylinder 8 misfire, explorer was stumbling and shaking at red lights (with a blinking CEL light which scared the living crap out of me) so went to investigate and about 1oz of water covering the spark inside the hole which led to the misfire, the coils were absolutely disgusting! full of dirt and crap from over the years (125k miles) so I cleaned them up and changed my plugs (NGK or oem Motorcraft will do just fine) if you have a different plug the explorer may not like them, just like my lexus suv wanted to **** out the bosch plugs I had put in (big no no) it was having random misfires like nuts! went back to oem and tada! Problem fixed, so depending on mileage, vehicle use and brand/type of plugs you are running plugs and or coils might be dieing! good luck hope this helps ya! :D

Sweet, thanks man! I didn't want to take a chance on ignition coils, but I decided to order another set of 8 anyways. I'm a little over 140,000, and I just changed the spark plugs. The spark plugs are Champion brand coppers, which might be part of the problem. I also had a specific cylinder misfire leading up to this, which for me was number 2. Once I cleared it, no CEL came back on until yesterday, but the misfires never stopped either. I just might have some water in the spark plug wells too, because i pulled the plug from cylinder 2, and it was already rusted for being 3 months old.

Will update when my coils arrive and I get them on, along with some new OEM spark plugs.
 






Sweet, thanks man! I didn't want to take a chance on ignition coils, but I decided to order another set of 8 anyways. I'm a little over 140,000, and I just changed the spark plugs. The spark plugs are Champion brand coppers, which might be part of the problem. I also had a specific cylinder misfire leading up to this, which for me was number 2. Once I cleared it, no CEL came back on until yesterday, but the misfires never stopped either. I just might have some water in the spark plug wells too, because i pulled the plug from cylinder 2, and it was already rusted for being 3 months old.

Will update when my coils arrive and I get them on, along with some new OEM spark plugs.

Yep them champions are making that fire breathing 4.6 angry LOL!! you should be back to normal once you get new coils and plugs in her! Good luck! :D
 






If that doesn't clear the code, then the next step would be to change out your plug wires. Had that problem also, but mine was the wires.
 






If that doesn't clear the code, then the next step would be to change out your plug wires. Had that problem also, but mine was the wires.

On the 4.0 v6 yes, but the 2002 - 2005 4.6L v8 all use ignition coil's.
 






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