My truck recently blew out spark plug #4. It's a 2000 F-150 super cab 4x4 with the 4.6l engine and a 5 speed transmission. It's got about 78k miles on it. All warranties are up, so it's up to me to fix it. There were still enough threads left in the head to get a new plug to stay in the hole. I was lucky. A new plug and coil and the truck's back on the road for now, but it's not going to last.

The engine had the mysterious ticking noise for about 2 weeks before the incident. I should have searched the forums for advice earlier.

I've got a bunch of questions about the blown spark plug problem and peoples' experience fixing this. Any advise is appreciated. I apologize if these questions are old news to some folks.

1. What's the difference between the 4.6l and 5.4l heads? Are they at the same risk for blown plugs?

2. What is the spec spark plug torque? Is a lower or higher torque a good idea?

3. How often should spark plug torque be checked?

3. Are different brands of spark plug more or less likely to blow out?

4. Timesert kit vs. Fulltorque kit: Which one is easier for a #4 (right rear) cylinder?

5. Where to buy the Timesert kit? Just call them on the phone?

6. Is there any need to remove the head before attempting repair?

Regards,
Bob _u

 

Well, I personally can't answer all of your questions because I have never personally experienced a blown plug, but I can answer a couple.

1) No difference, they both only have 4 threads per plug.
3) Once a week after changing them for about a month, then maybe at every oil change.
4) No, but these engines run best on Motorcraft or Autolite Double Platinums.

 

Thanks LXMan
That's a frequent torque check interval. Do you use a torque wrench or "calibrated" hand?

 

I don't know if it pertains, but check for a coolant leak right there at the heater core hoses.

The timesert can be done with the head on the engine. Don't know about the other, but I've heard it's a decent kit too.

The main cause of the problem is corrosion. The new autolite/motorcraft plugs are zinc-plated (galvanized) to keep this from happening as much.

My 2001 v10 has 7-8 threads in the spark plug hole.

Other than that, maybe visit the V10 forum to check out the FAQ - there's a posting in there about doing the plugs which explains a LOT. There is no difference between the V10 and the 4.6 except you have 2 less plugs

 

Thanks for the advice. I'll check the FAQ later. There was no sign of coolant leak on #4.

On this truck, the main cause is probably a lack of maintenance. Plugs were changed about 18 months ago and were never re-torqued. The plug probably worked loose.

Regarding corrosion, I always use a nickel anti-seize on plug threads for all engines. This should prevent corrosion as good as galvanized.

When all is fixed, the double platinums are going in. Re-torque will go on the calendar.

 

What is the recommended torque on the spark plugs for a 99 4.6L?

-Matt

 

bob_u, anti-sieze is your friend, which you'll find out reading that FAQ You definitely have the right idea.

Matt, 14 ft/lbs is the max we've been using in V10 land. My 4.6L '97, same thing.

11ft/lbs, I've read somewhere too, so don't jump to conclusions...

 

The plug blew out again yesterday. My wife limped the truck home. The repair kit from Timesert arrived today, just in time for the weekend.

Uh-Oh! The fuel rail is damaged. Now I need a new fuel rail. It did leak fuel, but thankfully no fire.

Pictures at
http://www.flickr.com/photos/bob_u/212879882/and
http://www.flickr.com/photos/bob_u/212879883/
This truck is going to be off the road for a few days.

 

No fire You are lucky at being unlucky I guess!

 

Back on the road Sunday night. $42 fuel rail from a wreck at a rural junk yard. Timesert kit was time consuming, but it worked as advertised. I can't beleive how much aluminum chips came out during the reaming process.

All wires and hoses are back where they belong, no MIL. Seems to run OK. Truck still has a mild shake (misfire) at idle and below 2000 RPM. This is same as before the spark plug incident.

 

You probably have a bad COP or a bad boot that's allowing the spark to go to ground at certain times. I'd suggest buying a new COP and playing round-robin with it.