I’ve read several posts on this topic but I haven’t seen any solid answers yet so I’m going to give it a go.
I just bought a 2004 F150 5.4 24 valve with roughly 235k miles.I personally just put a new reman engine in less than a week ago. Truck starts up just fine but has a miss on #7. I have triple checked all connections from the ECM to the oil pressure sensor. No other codes found other than #7 misfire. I have replaced the coil pack, plug, injector, and have even swapped those parts with other known working parts from the engine. I have done a compression test (roughly 185psi per cylinder) I have connected Noid lights to the coil and injector harness and have normal pulses. I am 💯 confused on what could be causing the misfire on #7 only. Any help would be greatly appreciated

 

Who's reman?
Is the misfire a hard mis present at idle? Or manifests in
steeper throttle angles, or random?
What's the plug look like?

If moving the OE coil, injector, (or completely replaced) and the misfire didn't follow with the position swap, and the noid showed a health pulse, then I'd be suspect of valve hang issues 'possibly' or a large vacuum bleed. Vacuum gauge show any rapid needle bounce ranging in a RPMs sweep? If the old engine management/electronics ops were normal prior to the reman install, I'd think any damaged connector/s would show up in the noid function after the work.

Sounds like you've covered the standard basics.

 

Reman meaning manufactured. The misfire is immediate upon starting. The spark plug looks great. I will do a leak down test next week and see if there’s something maybe in the valve train. I will also check the vacuum although I don’t recall a vacuum leak causing a miss just on a single random cylinder 🤷🏻‍♂️

The old motor was replaced because it had about 235k miles and had zero compression on cylinder 6

Thank you for your reply.

 

all the fords I have owned the number 1 cylinder is on the right side of the motor on the 5.4 triton it’s on the left I had the same problem as you but I was charging everything on the wrong cylinder.

 

One thing at a time, where did you get the info that told you #1 is on the driver's side?

There is a lot of ground to cover with this engine swap.

Where are you getting the info that it is #7 cyl?

I am a little uneasy with the info submitted in post #3 and there is a lot going on there.

 

#1 is passenger/right front..

My question was what brand/remanufactured engine did you purchase, or was it a local shop build?
A large vacuum leak would certainly show up in trim/O2 values. But if a valve train issue, a vacuum gauge would potentially rapidly 'bounce' the needle and not just be a low smooth reading like a larger vacuum leak would register. Doubt it's a valve/spring issue on a reman, but something to consider as everything else seems to prove out. A leak down would check the base engine, but if a valve/spring/guide issue may/may not be present on a static test. Plus, if a low cylinder, I'd think you detect a 'Gallup' when cranking the engine with ignition/fuel disabled.

 

The engine was bought through our local Napa store. This is probably the 5th or 6th one I’ve changed from Napa. Though this is the first 5.4 I’ve done personally, we’ve always had great success with their engines.

Keith, starting with the front of the engine on the PASSENGER side, the cylinders are numbered 1,2,3,4. DRVERS side front is 5,6,7,8. I hope that clears up any confusion. Not trying to sound like a dick but sometimes people get confused with they use “left side”or “right side” to describe which side of the vehicle they are working on.

I will definitely look a little deeper into vacuum leaks. My quick check I did Friday just consisted of spraying some break clean or starting fluid around vacuum lines, the intake itself, and that PITA main vacuum hose coming off of the bake booster to the intake manifold.

Thanks for your replies

 

Keep us updated.

I was in a Ford commercial fleet industry for 34 years.
I've installed NAPA units as well with good luck. We did switch to Ford remans later on as builds became more complex (sometimes part quality came into play on aftermarket units, not just NAPA) . More so on bolt on parts failing, usually off shore supplied had a much higher failure rate. Although a global market anymore..

We did get into warranty issues (labor) a few times on reman engine work. As well as independent Machine Shop builds. Usually somewhat minor, but at times failures caused route and repair location issues.


Being the original engine and powertrain management didn't point a boney finger at #7, unless damaged of some sort (noid seems to support ops though ) occurred , and injector/coil/plug swap positions aren't seeing a move, and vacuum values are reported as stable at idle, doesn't leave much but mechanical.

Whats the trim and O2 values?

Anyway, sometimes the best way is to prove out whats it's not, and move forward in reverse.

 

It would help a lot if we knew just what kind of test equip you have to use.

From there we should be able to suggest some tests that could help pin down where the problem lies.

 

I’ll be back to the shop on Tuesday and get the exact model Snap On scanner I have as well as the O2 and trim values.
I appreciate all of your help