Bad Injector plug causing misfire

[Ifixyawata]

On the way home from a hockey game we started getting misfire codes off and on. When we got home I checked cyl three and saw this.

This is the suspected culprit of an intermittent misfire. On the way home got off and on codes for misfire, about 90+% cyl 3 (pictured) and a few for 4 that I'm thinking are false codes?

I'm going to peel back this goopy tape and see what the issue is, I suspect somebody tried to tape over a bad wire. The other cylinders don't look this way.

Oh also this is the 2014 Expedition in my signature.

 

[Ifixyawata]

Okay so that wasn't it even though that wire was mangled. Currently swapped coil 3 and 1 trying to get a misfire code. Seems like the misfire clears up above 2k rpm

 

[Ifixyawata]

Now I'm consistently getting 3 and 4 misfire

 

[ls1mike]

Did you put a scanner on it?

 

[Ifixyawata]

Did you put a scanner on it?

OBD2 Bluetooth scanner is giving me cyl3 misfire and still cyl4 misfire along with random/multi misfire.

 

[ls1mike]

So P0303, P0304 and P0300? I am wondering if you have a failing CPS. How many miles?

 

[Ifixyawata]

So P0303, P0304 and P0300? I am wondering if you have a failing CPS. How many miles?

149k

 

[ls1mike]

I would really start testing coils on a 5.4.

 

[Ifixyawata]

I would really start testing coils on a 5.4.

I swapped 1 and 3 and the misfire code remained on 3.

 

[ls1mike]

I swapped 1 and 3 and the misfire code remained on 3.

Now you need to check all the wiring and the injector itself. I had a bad injector on the Trans Am which caused a misfire.

 

[Ifixyawata]

Now you need to check all the wiring and the injector itself. I had a bad injector on the Trans Am which caused a misfire.

I pulled and replaced the cylinder 3 plug with no improvement. Definitely feels like it's got two dead cylinders at least. I will have to check more tomorrow. I'm second guessing my coil swap now, thinking I might have not switched them at all.

What's the easiest way to check an injector?

I'm still stumped as to why this is localized to 3 and 4.

 

[ls1mike]

That is the plug you pulled out? That is horrible. What do the rest of the plugs look like?

 

[Ifixyawata]

That is the plug you pulled out? That is horrible. What do the rest of the plugs look like?

Yes, that was living in cylinder 3. I'm not sure about the rest but I'm going to pull 4 out once it cools down. I've swapped and reseapped coils and tr misfires remain on 3 and 4.

What would cause this plug rust? Old coolant leak?

 

[ls1mike]

Man, I was thinking coolant leak. It looks like rust to me.

 

[SHOZ]

What is the gap on the one you pulled out compared to spec?

 

[paulo57509]

I had a misfire on the Legend due to a partially plugged injector. After eliminating the ignition as the cause, I looked at fuel.

I checked each injector individually with a fuel pressure gauge and an OTC injector tester. The offending injector didn't show as great a pressure drop as the remaining injectors.

I inherited the OTC tester. I bought one of these but never used it:

https://www.amazon.com/ALLOSUN-EM276SET-Injector-Adapter-Cleaning/dp/B07VC37VRB/ref=sr_1_1?crid=1XB3G67QIC522&keywords=fuel%2Binjector%2Btester&qid=1706488837&refinements=p_89%3AALLOSUN&rnid=2528832011&s=automotive&sprefix=fuel%2Binjector%2Btester%2Caps%2C176&sr=1-1&th=1

 

[Ifixyawata]

The long awaited conclusion to this dead misfire seems to be here. After checking and rechecking and getting a poor, low effort dealership diagnosis, it seems to have been a broken valve spring this whole time. About 10 miles of driving and lots of idling and so far so good. The nightmare may just be over.