Cylinder Misfire - Tried everything I can think of?

[Johnny Glenn]

Thanks for looking in - I've got an 03 Ex w/ a 4.0 that runs terrible when first cranked - misfires and sputters for about 30 seconds but then runs perfect from then on out. Shut it off and it cranks fine etc. Everything I can think of has been replaced - plugs, wires, fuel filter, some injectors, coil, O2 sensor, cam sensor - nothing fixes that initial cold start. Code has read random misfire but also had coded 3 and 5 misfire. Any ideas on what to try? Thanks

 

[patrick112390]

might be worth having the dealer check it out... there is a pcm reprogram for various things- cold start issues included. If it doesnt already have the latest calibration...

 

[Johnny Glenn]

Thanks -- She's heading to the dealer Monday morning -- I give up on this one!...unless anyone else has an idea..? Thanks again

 

[wood1]

It might be a good idea to throw a fuel pressure gauge on prior to that first start to see what the pressure is doing. At least you could rule it out as an issue.

Ever check the crank sensor?

 

[Johnny Glenn]

I just purchased this Explorer and someone before me was chasing this problem. The plugs were gapped wrong but wires, sensors, coils, injectors look new. I'll try fuel pressure - thanks.

 

[dbailey]

I just purchased this Explorer and someone before me was chasing this problem. The plugs were gapped wrong but wires, sensors, coils, injectors look new. I'll try fuel pressure - thanks.

What was result of fuel pressure? Problem fixed? I am having a #5 misfire after a new long block being installed. Am hoping its not an injector. After $5,000 for the long blocked installed, I am broke! Mine misfires when first started and then when the gas that is on the plug burns off it runs fine. Only happens after starting it when it has sat for awhile. Ran a can of seafoam thru tank and gonna try another one thinking maybe there is something there. If not, then the mechanic that installed the engine is thinking the #5 injector is leaking down and dropping gas onto the plug then when its running a minute or two the gas burns off and it seems to run fine. Anybody have an idea or suggestion? Thanks.

 

[esclamada]

have you tried swapping injectors and cops and check if the misfire code is still pointing at #5 ?

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[dbailey]

have you tried swapping injectors and cops and check if the misfire code is still pointing at #5 ?

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Thanks for suggestion. Haven't tried that but removing that plenum (while I've never done it before) looks like a beast of a job! If I gotta remove the plenum to get to the injectors would it not be better to just replace the injector and go from there? The service manual I have says its like a 21 step process.

 

[WA7S0N]

Be careful when using Seafoam. It works wonders on cleaning all that gunk out, but I've heard from several mechanics that it can actually foul some of your plugs. I've never tested it personally, but I've always been told to run a whole can in a tank with less than 1/4 tank of gas and before you plan on replacing your plugs (because of the potential to foul them).

To save time and money it may be worth looking into.

 

[dbailey]

Be careful when using Seafoam. It works wonders on cleaning all that gunk out, but I've heard from several mechanics that it can actually foul some of your plugs. I've never tested it personally, but I've always been told to run a whole can in a tank with less than 1/4 tank of gas and before you plan on replacing your plugs (because of the potential to foul them).

To save time and money it may be worth looking into.

Thanks for the input. I've already run a can thru a tank and under the mechanics recommendation put another in a full tank and ran it down to less than a half and filled it back up. Of course the Seafoam didn't fix what we both hoped would be the problem (gunk in the injector). Looks like I'm replacing all 6 injectors and hope that fixes it. It still rough idles on start-up then smooth soon afterward. A bit of rough idle when I go to turn it off, too.

 

[chakaD]

It really isn't that bad. I had the hood off for more room, and I recommend you do. Made it so much easier to get to the back bolts.

Thanks for suggestion. Haven't tried that but removing that plenum (while I've never done it before) looks like a beast of a job! If I gotta remove the plenum to get to the injectors would it not be better to just replace the injector and go from there? The service manual I have says its like a 21 step process.

 

[WA7S0N]

Thanks for the input. I've already run a can thru a tank and under the mechanics recommendation put another in a full tank and ran it down to less than a half and filled it back up. Of course the Seafoam didn't fix what we both hoped would be the problem (gunk in the injector). Looks like I'm replacing all 6 injectors and hope that fixes it. It still rough idles on start-up then smooth soon afterward. A bit of rough idle when I go to turn it off, too.

Something else you could try (if you don't mind spending ~$60) is go to Valvoline and have them clean your fuel injection system. Made a big difference in my truck and got rid of the small hesitation I had. It was unreal how much black smoke was coming out of my exhaust (gunk they cleaned out). It's also worth noting that they advertise this service as something that will bring your truck's fuel injection system performance back to near stock conditions. I've recommended this to a few buddies and they all said they noticed an improvement.

If you've got half a dozen tens laying around, I'd give them a call.

 

[dbailey]

Something else you could try (if you don't mind spending ~$60) is go to Valvoline and have them clean your fuel injection system. Made a big difference in my truck and got rid of the small hesitation I had. It was unreal how much black smoke was coming out of my exhaust (gunk they cleaned out). It's also worth noting that they advertise this service as something that will bring your truck's fuel injection system performance back to near stock conditions. I've recommended this to a few buddies and they all said they noticed an improvement.

If you've got half a dozen tens laying around, I'd give them a call.

Thanks again for that great idea! I've already bought the injectors so I guess I gotta bite it and go with them. The ones in the truck have over 265,000 miles on them so I guess it can't hurt unless injectors don't "wear out" over mileage.

 

[WA7S0N]

Thanks again for that great idea! I've already bought the injectors so I guess I gotta bite it and go with them. The ones in the truck have over 265,000 miles on them so I guess it can't hurt unless injectors don't "wear out" over mileage.

You're welcome, and that's true. I was just trying to save the time and effort associated with changing your injectors. I don't think their is a happy medium when it comes to injectors, they either work or they don't. They could have an increasing buildup of deposits over time, which could significantly hinder their performance though. Changing them all together would be the better, more permanent solution though, IMO.

You're a more motivated person than myself. I'd just rather have them cleaned than replaced haha. Then again, I've only got about 145,000 miles on mine.