#7 Misfire after spark plug ejection
#1
11-30-2016, 06:04 PM
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#7 Misfire after spark plug ejection
Hello
My brother recently bought a 1999 F150 V8 4.6L with 160k miles.
On the highway the #7 spark plug blew out a few months after purchasing.
He took it to a mechanic in the middle of the night and he replaced the spark plug and wire for #7 and sent him on his way.
Now, #7 has been misfiring on and off after the engine heats up. It seems to stop misfiring at higher rpms after 1700 or when you reach about 65MPH. Its also making a pretty loud clicking noise, both while misfiring and when not.
I replaced the coil pac on the driverside that does the #7 (it is NOT COP), and the mechanic replaced the #7 plug and the #7 wire.
Also, I read this "and just an fyi, if that mechanic used a helicoil, he may have screwed a valve(view pic in the link below).http://www.blownoutsparkplug.com/images/100_8593.JPG" on a different forum post and it sounds vaguely familiar. The mechanic may have used one I cant find the receipt and my brother doesnt remember the name of the mechanic.
Whats my next step?
Any suggestions would be greatly appreciated, we cant afford much. Thanks guys!
My brother recently bought a 1999 F150 V8 4.6L with 160k miles.
On the highway the #7 spark plug blew out a few months after purchasing.
He took it to a mechanic in the middle of the night and he replaced the spark plug and wire for #7 and sent him on his way.
Now, #7 has been misfiring on and off after the engine heats up. It seems to stop misfiring at higher rpms after 1700 or when you reach about 65MPH. Its also making a pretty loud clicking noise, both while misfiring and when not.
I replaced the coil pac on the driverside that does the #7 (it is NOT COP), and the mechanic replaced the #7 plug and the #7 wire.
Also, I read this "and just an fyi, if that mechanic used a helicoil, he may have screwed a valve(view pic in the link below).http://www.blownoutsparkplug.com/images/100_8593.JPG" on a different forum post and it sounds vaguely familiar. The mechanic may have used one I cant find the receipt and my brother doesnt remember the name of the mechanic.
Whats my next step?
Any suggestions would be greatly appreciated, we cant afford much. Thanks guys!
#2
11-30-2016, 07:54 PM
I would do a compression check on that, no, all of the cylinders and see how that one compares to the others. There could have been damage to the rings, cylinder walls, etc from when the plug blew or from when it was repaired.
I don't know if they make an ignition analyzer that will work with the coil per plug engines but I'd find out and if they do I'd check the ignition circuit with that. They will show and isolate up a surprising number of faults if one knows how to use one properly.
Also don't assume that the new spark plug is good. MOST of the auto parts being sold today are not tested and a lot of them are bad right out of the box.
The clicking sound could be a sign of physical damage. Are you sure that it's coming from that cylinder?
Someone with a borescope could take a look at the inside of the cylinder through the spark plug hole and may spot any damage.
I don't know if they make an ignition analyzer that will work with the coil per plug engines but I'd find out and if they do I'd check the ignition circuit with that. They will show and isolate up a surprising number of faults if one knows how to use one properly.
Also don't assume that the new spark plug is good. MOST of the auto parts being sold today are not tested and a lot of them are bad right out of the box.
The clicking sound could be a sign of physical damage. Are you sure that it's coming from that cylinder?
Someone with a borescope could take a look at the inside of the cylinder through the spark plug hole and may spot any damage.