Just changed my valve cover gaskets. What did I mess up?

[OskarBlue]

So I just changed my valve cover gaskets, upper intake manifold gasket, and spark plug wires. When I did a test drive, I found my engine was running rough, and the truck really doesn't want to accelerate. Upon acceleration I heard knocking coming from the engine. Help me figure out what I might have done wrong?

No CEL so I can't check for codes.

Here's everything I did:
- removed/disconnected everything in the way in order to remove upper intake manifold and valve covers (vacuum hoses, throttle body, ignition coil, etc.)
- replaced upper intake manifold gasket
- replaced valve cover gaskets (this was the main reason for all the work)
- replaced spark plug wires (plugs were changed ~2k ago)
- drained/refilled cooling system
- replaced fuel filter
- changed oil/oil filter

I'm certain the plug wires are all going to the correct cylinders and are seated correctly.

I'm reasonably certain I did all the gaskets correctly, but could I have done something wrong with them?

My suspicion is vacuum leak, but this is outside my realm of experience so far. Could I have not reconnected a hose properly, or disconnected something unknowingly? I'm about to go double check them all and spray them all with carb cleaner and see if I turn up and leads.

I did find a degraded vacuum hose (dry rotted) I want to replace, but haven't done it yet. It worked fine before. Could handling it have caused it to fail? Would that be causing this large of an issue?

Could I have messed up my MAF sensor somehow?

Any other ideas for things I could have done wrong that would be causing the problems I'm experiencing? Would appreciate any input!

 

[RonD]

Spark plug wires, check them again and then a 3rd and 4th time..........
Coil pack only has 3 coils inside, each coil sparks TWO spark plugs at the same time

3.0l has these match pairs in firing order, 4.0l is the same
3 4
2 6
1 5

so they MUST BE sharing the same coil in the coil pack
Can be as above or
1 5
2 6
3 4

One side will be 1 2 3, the other side must pair match, 5 6 4
1 with 5
2 with 6
3 with 4

Ford numbers cylinders this way
3 6
2 5
1 4
front
And coil packs are often MISWIRED to look like that
And miswired coil pack can cause a knocking noise


After engine is warmed up and idling, unplug the two wires on IAC Valve, it will close
RPMs will drop to 500 or engine may even stall, either is GOOD, it means no vacuum leaks
If idle does not drop then yes you have a vacuum leak

 

[OskarBlue]

That's a useful trick!

When I unplugged the IAC valve, the RPMs did drop down to 500 and it sounded like it was close to stalling. So it's likely I don't have a vacuum leak?

I've triple checked the plug wires at this point. They're definitely all correct.

Also verified the fuel filter is connected properly.

Anything else it could be?

The engine sounds like it's chugging to me, and if I leave it idling the RPMs vary and will end up going down to almost 500.

 

[RonD]

If battery was unhooked it can take 2 or 3 drive cycles for computer to relearn engine settings.
Computer has a KAM(keep alive memory) just like radio has, holds time and presets.
When ALL power is disconnected then Radio and computer lose KAM data

IAC Valve settings for RPM and TPS(throttle position sensor) settings are two learned settings, so wandering idle is not unusual after battery disconnect or new sensor installed.

One Drive cycle is full warm up(ECT above 170degF) and then full cool down(ECT below 140degF)

If it has already been a couple of days/cycles then check fuel pressure, low pressure can cause "knocking/pinging" noise
1999 Ranger fuel pressure should be 55-65psi running, then hold pressure above 45psi when key is off

 

[Doofy]

What brand plugs did you install? Ford's prefer motorcraft. I installed e3s my first tuneup and the truck would barely run. Wasted lots of time checking wires and things only to find the fancy plugs were the problem.