2003 4.6L Stalling/Missing

[hpfiend]

Hey all-

My dad has a 2003 4.6L Explorer Limited. It has about 65K miles on it and recently has started stalling and missing. It does not have any codes via code reader or lights on the dash. Fuel pressure does not change when it misses while driving. Sometimes it will stall when idling in park, sometimes when switching between park and drive, sometimes park and reverse, sometimes when driving down the road it will miss and then beep like when you turn the key on but nothing else happens, it will miss under load and cruising. Now that I describe it, it sort of sounds like an ignition switch issue--- I am going to go fiddle with it and see if I can get it to happen...

Any ideas?

Thanks!
Andrew

 

[rocco123]

IAC valve likely. You may want to swap ignition relay with maybe the blower relay for troubleshooting.

 

[Snowcone]

What and where is the IAC valve?
My 4.6 is doing similar things.
Intermittent miss at load, no codes showing but an occasional beep.
Plugs look OK but I am going to replace them and the coils anyway.
Sometimes you can tow a caravan and it is perfect, next day it will start missing at 1500 to 2000 revs (sorry if this is a hijack but the symptoms sound the same)

 

[matt0248]

What and where is the IAC valve?
My 4.6 is doing similar things.
Intermittent miss at load, no codes showing but an occasional beep.
Plugs look OK but I am going to replace them and the coils anyway.
Sometimes you can tow a caravan and it is perfect, next day it will start missing at 1500 to 2000 revs (sorry if this is a hijack but the symptoms sound the same)

The IAC is on the front side of the intake plenum (intake elbow) , but It will not cause a misfire or rough running under load. You are probably on the right track with the plugs and coils.

 

[roccov]

Looks like we may be having similar issues.....

 

[hpfiend]

Is there an easy way to diagnose the coil packs?

I checked ignition switch for jarring, going to clean IAC and look for vacuum leaks today even though it is missing under load.

Will keep posted.

 

[roccov]

OHM resistance check between the primary and secondary resistance points. From the left pin to the spot where the boot plugs into the plug, mine were running around 5.5 ohms

Have you changed the boots and coils? This happened to me once before and I just did plugs, rubber boots and coil springs and it was good to go.

 

[hpfiend]

Thanks! To clarify however is 5.5 ohms good or bad? By coil springs do you mean inside of the boots?

 

[roccov]

Thanks! To clarify however is 5.5 ohms good or bad? By coil springs do you mean inside of the boots?

Yes and Yes. There may be some variance between the coils but that's ok. As long as you're not reading say less than 5.3, 5.4. Use your best judgement. If one is bad, you'll notice a large difference in ohms from the rest.

 

[roccov]

I think the acceptable ohm reading is 5.5 but mine fluctuated between 5.4 to 5.6.

 

[hpfiend]

IAC had no effect

 

[RedHawk]

Is there an update on this thread or anyone else gone through these symptoms and what was the fix? Mine is doing it now, and I've got a 2003 Explorer with the 4.6 engine.

Hawk

 

[Snowcone]

It was coils causing my misfire issues, so I replaced them all.
Runs perfect now