Misfire problems

Maintenance/Repairs
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1

I’m having problems with my 4.6 L explorer sport trac. Got a code for a number 8 cylinder misfire. I swapped the fuel injector with the cylinder next to it and disconnected the battery to reset the system.
The check engine light went away, but now I’m getting a lot of hesitation and vibration. I thought I might of unseated one of the othe injectors, so I disconnected the fuel rail again to reseat them all, but the problem is starting to come back.

I still don’t have a check engine light coming on, and I’m at a loss for what to do next. Any ideas?

2

“unswap” the injectors, ie, return them to the original order.

1 Like
3

replace what used to be injector 8.

4

So it took a few days and my check engine light came back on. I left my fuel injectors swapped. The code reads a miss fire #8 cylinder. Going to replace my spark plug today and see what happens.

5

Also check the electrical plug at the coil.
As they are just plastic clip on plugs, they often break in such a manner as to not plug on tightly. . then work loose later.
If it does not snap tight when you plug it in , you may need a new pigtail .

6

Do you have coil on plugs there on your explorer ? If so, I’d guess that’s where the problem lies. No harm to check the spark plug first of course, easy to do. If that’s not it, try switching the coils around, or installing a new coil on number 8.

7

You have not stated how many miles on this thing but if the plugs are out you should check the compression.

One can throw every part in the book at it but if a cylinder is dropping it will all be a waste of time and money.

8

I’m sitting at 91003 miles.
I ended up putting a new spark plug in cylinder 8 after my check engine light came back and the code was misfire in number eight cylinder again. This was after I swapped the fuel injectors originally, I never did swap them back.

Here is a pic of the spark plug I took out. The guy at the auto parts store said that it looks like rust. Keep an eye on that spark plug and if the same starts to appear on it the I have a head gasket problem or worse.

IMG_0152.JPG2448×3264 1.56 MB

After swapping it out the truck seems to be running fine. No hesitation or vibration.

9

Do other plugs have that same appearance? If your trips are mostly short ones, that might allow a little rust to form below the threads on the spark plugs without head gasket involvement. The chemical reaction of exploding gasoline inside the cylinder is ch2 + o2 == co2 + h20 , and that last one is water, which could cause some rust to appear on the spark plug I suppose. Suggest to ask your shop to check the pcv system, as it is partly involved in keeping the crankcase from building up water vapor from blow-by gasses.

10

You’re LUCKY you got that spark plug out in one piece

I don’t know what your method is, but I advise slow and steady, using lots of penetrant

You’re at pretty much the mileage where you should do the remainder of the plugs

Now that I see your plug, I also know what ignition system and engine you have. Heads up, the coils are also known for causing a misfire. They tend to fail when hot. So if you have another misfire on #8 cylinder next week, it’s probably not the plug again, it’s probably the coil.

We have lots of trucks in our fleet with that same engine family, and we never leave them in there as long as you. We change the plugs and boots at 60K intervals.

I’m not condemning anybody. I’m just giving some advice.