background: explorer ran fine for a year or so after I bought it, however would notice sometimes at WOT the CEL would flash briefly till I let off the gas, and it would accelerate and run fine

fast forward to a week ago, I finally got a CEL that was constant...ran the code and got p0306...misfire cylinder 6...I knew the wires needed changing, so I swapped those out, seemed to work for a bit but then it came back.

check the codes again and I'm getting p0306 and p0304, seems to have grown to cylinder 4 as well. The CEL flashes while driving, but remains solid if I roll for a bit and am at a stoplight, until I accelerate again, then in blinks.

I checked the coil pack via some method I found on here, it seems in spec, the secondary readings were all pretty much identical, and the primary one gave me 1.1-1.3 ohms on all 3 pins.

the fuel filter was replaced less than 15K ago...along with the plugs. the 6th cylinder plug didn't look that different either, I was going to swap the plugs from bank 1 to bank 2 and vice versa to see if that helps, but I'm kinda stumped now? I was reading that vacuum leaks could cause that, but I took starting fluid and sprayed it around connections with no noticeable engine revving, I would think a vac leak would cause something more broad than just two cylinders... I cleaned the MAF tonight and it didnt help.

possibly the intake manifold gaskets? or possibly the injectors as well because if I clear the codes and let it idle for awhile, while the idle is kind of erratic, the CEL light never comes on, and nothing gets stored until I put the truck under load.

I plan on doing a compression test this weekend to see if i can eliminate valve damage or something more major

It just seems weird to me that its only cylinder 4 and 6 but skips 5, so its not that whole bank...I'm starting a new job in a month or so, but i commute like 110 miles a day and I need this to last me another month or two (it has 255K on it, so a new vehicle is in the cards)

 

Did you happen to get the least expensive spark plug wires available, or some higher grade wires? I've seen some rather poor crimps on the cheap spark plug wires, and heard of some folks who had cheap wires that were never even crimped, just kind of rolled around the wire.

If you bought the cheap wires, you might want to try returning them as defective and ask if you can pay the difference and get the next grade (or maybe two grades) better.

If you are pretty confident the wires you purchased are quality wires, then double check to make sure you have them completely seated on the coil and spark plug ends. If you are not getting a click or feeling an obvious snap, they probably are not seated fully. If the wires for cylinders 4 and 6 are similar in length to other cylinders, try swapping the wire with another cylinder. While you're at it, you might try swapping the spark plugs on 4 and 6 with yet again different cylinders (such as swapping wires with cylinders 1 and 3, then plugs with 2 and 5). See if the misfire codes remain on cylinders 4 and 6 or follow the wires or the plugs.

You'll also want to make sure you are numbering your cylinders correctly. Ford does it different than GM and Chrysler and I'm not sure what your background is. For a Ford, if you're looking at the belt side of the engine (front of the engine for an Explorer) cylinder 1 will be the front cylinder on the left. The cylinders are numbered sequentially down that side to the firewall. Then, assuming you have a 6 cylinder Explorer, #4 is at the right front and #6 is next to the firewall, with #5 in between.

-Rod

 

I did get the 2nd grade up from the cheapest wires, and I'm fairly confident I seated them properly. I was kinda surprised as how "wiggly" the connections appear at the spark plug side, but I'm confident they are properly attached.

I was getting the p0306 code with my old wires, which I assume were Ford OEM as they were numbered and IIRC had motorcraft printed on them.

I'm gonna try the swap game with the plugs when I do my compression readings and see where that gets me

 

Go to this link and make sure your plug wires are connected the same as this LINK.

 

Go to this link and make sure your plug wires are connected the same as this LINK.

 

everything is hooked up correctly...I'm not that much of a newb haha..

anyways.... i figured I'd check the codes again this morning, and I realized I never checked the "pending codes" (an option on the smartphone app torque)...I'm getting P0174 as a pending code now...so it looks like that's pcv related? would that be a trigger to the misfire codes? The pcv valve is cheap and I've never changed it since I've owned the car so I'll probably do that this weekend too.

 

The elbow for the PCV is a more common source of the P0174 code due to the vacuum leak it provides. A vacuum leak could contribute to a misfire code, but interesting that the misfire isn't reporting an issue for an entire bank of cylinders if that were the cause. Have you tried swapping plug wires and spark plugs around yet?

-Rod

 

i bought new wires because the old ones were a little beat up (probably didnt need to, but I did) tomorrow im gonna take a compression test and see what i get...if that comes back clear I'll start swapping plugs around, and then if that doesnt work probably swap the o2 sensor and/or fuel injectors and see if the code follows. i decided to take the codes again and I'm getting pending codes p0174 as well as p1151 (NEW ONE!) and the stored codes are the 4 & 6 misfires

 

I may have missed it somewhere above, but what are the vehicle details (year and engine, SOHC/OHV if V6)?

The P1151 pending code is another one pointing toward a bank 2 lean condition. The good news is everything so far is pointing toward something that would impact only bank 2, so that might narrow your search.

-Rod

 

looks like it was the injectors...considerably lower resistance reading on my dmm than the other 4...went to swap them out only to find the little insulator pieces were cracked to ****. Going to pick those up at the dealership tomorrow. Will report with hopefully no CEL tomorrow night!

 

swapped all the injectors on bank 2...everything runs fine! thanks for all the input everyone!

 

Good find, and thank you for the follow-up!

-Rod

 

I have a P0301 and a P0305 misfire. Hopefully it's not an injector. Came across this nice article for everyone

Part 1 -How to Test the Fuel Injectors (Ford 4.0L)