4.0 #4 Stuck Spark Plug?

[Charlie M]

A month into my '10 Ranger 4.0 with 135K miles, runs great - some rough idling. Some chain slap at startup. Now OBD lights up - Code indicates #4 misfire. I reset OBD and it reappears. Tried to pull #4 plug and get a view, but its so very tight. With solid but careful force with my 18" breaker, I get maybe 1/8 turn out of it and a sudden hard stop. I tried to slightly re-tighten, but it's not budging either way. Investigating the web, a UT video indicates this is common, suggest spray and soak 1-2 days with combo of PB Blaster and Brake cleaner solution. I've done that and waiting but really uneasy about snapping the plug and a cyl. head redo. Drivers side so possible, but even with that it looks scary for this old school shade tree guy. While waiting, I'm shopping replace/rebuild options just in case. The plug in there does not look original (no red paint tip) and the Oil Filter I replaced was apparently put on by a gorilla and think this engine likely has been abused by a neanderthal. PLEASE any hope or advice?

Greatly appreciated!!

 

[Uncle Gump]

Did you try running the engine up to operating temp... shut down... then try to remove it?

 

[Charlie M]

Good point. It was barely warm my first attempt. Tomorrow, allowing the 1-2 day PB solution soaking, will try again after a full warmup. Thank you! Very much appreciated and will advise.

 

[sgtsandman]

It depends on the individual engine. Hot might work and on other engines, it has to be stone cold.

Stone cold worked on mine.

 

[Charlie M]

Thanks for the assistance here!

I tried cold before hot today after 2 days of soaking. This time, 1/8 tough turn at a time on 18" breaker, it slowly gave it up and came out - very tight the whole way. The starting threads look rolled to me and lots of build-up on the threads and seat. Insulator looks a bit dark and it could be using coolant now it seems. It mysteriously ran warm last drive and found low after sitting these 2 days. No drips/leaks and will refill in case it was a second burp. I replaced a leaking thermostat housing 2 weeks ago. Something is going on with this motor, but #4 plug better looking than feared (i.e. oil drenched). The Bosch Dbl Plat. showing some wear but I'm not ready to do a full tuneup being not convinced. Clean and replace #4 for now is most likely tiny step.

I'm wide open to any thoughts / inputs please as I plan next steps toward hopefully getting her in a "road trip ready" type of shape. I'm thinking with the OBD calling #4 misfire and low emissions efficiency codes, and if it is now found burning/using coolant, I likely have a deeper issue here. A head gasket or a crack somewhere (head or block) and the game could be over for this old power plant as-is at 135K Maybe R&R this driver side head with block in truck to check gaskets and any cracks. If nothing then the whole thing will have to come out for a rebuild or replacement.

Hope to avoid the parts trap but also really need my truck on the road ....

 

[sgtsandman]

The heads on the SOHC have a reputation of being pretty reliable. So, it could be a gasket. An compression test might tell you something. If the compression test looks good, you might need to do a leak down test.

Others might have some more/better suggestions since I am not a professional automotive mechanic.

 

[Shran]

You have nothing to lose by chasing the threads at this point and throwing a new plug in it. That’s what I’d do before jumping to any conclusions.

 

[Uncle Gump]

Chase the threads...

Throw the Bosch plugs in the garbage.

I'll personally only run Motorcraft or Autolite plugs.

 

[Bgunner]

I agree with the consensus. You may also find that once the plugs are changed that the "low emissions efficiency codes" may go away.

If you are concerned about burning coolant pulling the plugs, reading them then a compression test is the best way to be sure. If a head gasket blows between the cylinder and the coolant port you will get exhaust in the coolant system. There are testers for this using dye in a tube but often putting a rubber glove over the radiator fill port with a rubber band to seal it will show you if this is happening. The glove will fill with air and flop around.

Fix the skip and go from there.

 

[Charlie M]

I replaced #4 plug, reset OBD, and drove about 30 miles yesterday. OBD repeating "#4 misfire" code (2x) only. No "low emission efficiency" code so far. Rad coolant down .50 - .75 inch from top after prior cold top-off, but no higher level in the recovery tank. Noticed from upper hose, when cold, system appears to retain pressure (?).

She's peppy and runs great while moving, but real bad rough idle can show up at stoplight (#4 dead ?) mainly after coming off from traveling the interstate at speed (70). It does self-correct shortly after moving again.

Checked oil cap and now see some micro bubbles in there even after cool down (pic). I'm leaving the rad cap loose for now and will monitor closely.

Will plan to do compression and leak down tests on both banks to investigate more deeply - maybe this weekend. Confident now about how to get any other seized sparkplugs out. A bit worried I've got a driver side head gasket at a min. on my hands. Will advise when more is learned, and I very much appreciate the great support I've gotten here. Thank you!

 

[19Walt93]

The threads on your old plug are coated with carbon, that's why it came out so hard. Three valve 5.4's had that problem in spades and my techs would warm the engines, replace the plugs on one side, warm it again and do the other side- no one ever broke a plug.
It migh be worth running some combustion chamber cleaner through it before doing anything drastic, you likely have carbon on the valves, too. Just keep an eye on the cats while you feed it the combustion cleaner, they'll get hot fast.

 

[Uncle Gump]

I've also seen where spark plugs don't get tightened properly and carbon is allowed to follow the plug threads. Makes removal difficult.

I was also serious about pitching the Bosch plugs. I've had zero luck with them in anything Ford.

 

[Charlie M]

The threads on your old plug are coated with carbon, that's why it came out so hard. Three valve 5.4's had that problem in spades and my techs would warm the engines, replace the plugs on one side, warm it again and do the other side- no one ever broke a plug.
It migh be worth running some combustion chamber cleaner through it before doing anything drastic, you likely have carbon on the valves, too. Just keep an eye on the cats while you feed it the combustion cleaner, they'll get hot fast.

Thank you! Really good to know about the carbon build up and the 5.4's. Plan to do a thorough combustion chamber cleaning if I get decent compression / leak measurements to try and resolve the persistent mis at 4.

 

[Charlie M]

I've also seen where spark plugs don't get tightened properly and carbon is allowed to follow the plug threads. Makes removal difficult.

I was also serious about pitching the Bosch plugs. I've had zero luck with them in anything Ford.

Lose plug allowing carbon to creep makes a lot of sense. Will do the MC or AL 6 plug replacement as I get them all out for the tests.