Engine & DrivetrainEngines and Drivetrains can be a major problem for a lot of vehicles. If you are having engine or drivetrain problems, you can post your questions/concerns about the issue. Furthermore, if you are in the process of doing an engine rebuild, post your progress with pictures.
Per the thread in the link above, the first time I replaced the spark plug four months ago, the engine's misfiring went away. Today, though, the misfire came back, same cylinder. I replaced the spark plug tonight, but this gave only a very marginal improvement. (Still misfires, but not as badly.)
Aforementioned thread had a recommendation to replace the coil-on-plug, but at $50 each, I'm at the point where I need to get a proper diagnosis. I have no diagnostic tools. One thing that I discovered both times that I replaced the spark plug was that the spark plug well was wet. When I pulled the plug, the part of the plug inside the firing chamber was clean and dry, but the outside part, connected to the coil boot, was wet. Not sure what the wetness was, as there was no discernable odor. When I wiped it with a white paper towel, it stained the towel a light brown color. The engine oil is a darker shade (almost time for oil change). Could there be a gasket problem causing this?
__________________ 1999 Merc Grand Marquis
4.6L engine
144K miles
Need it to go another 144k
I am a relative novice to car repair. I've replaced plugs & wires and this year I learned how to replace brakes and did so on three vehicles. It looks like I'll be learning how to replace the exhaust system very soon. "Back in the day" I'd been known to replace radiator or two and a water pump once, but that was before you'd have to take apart the entire front end to do so. (Shoulda kept the '74 Cougar with the 351.)
I assume that you had your codes read and that is HOW you know that it is the same cyl misfiring.
Swap the suspected bad coil with another one, perhaps the adjacent one. IF the misfire moves with the coil, then you know that the coil is bad.
__________________
BroncoJoe19
2006 Alt Fuel Jeep (electric)
'98 windstar 3.8L
'99 Crown Vic 4.6L
'90 Full Size Bronco 5.0L
I'm not a professional mechanic, take my suggestions with a grain of salt, or a cup of coffee
At the bottom of each post there is a little icon
Clicking it gives feedback to the moderators, and poster regarding which posts are most helpful.
I assume that you had your codes read and that is HOW you know that it is the same cyl misfiring.
Swap the suspected bad coil with another one, perhaps the adjacent one. IF the misfire moves with the coil, then you know that the coil is bad.
Thanks Bronco Joe!
OBD-II reader pulled a P0304 code.
Good idea on swapping coils. Do the wires that attach to the top of the coil disconnect easily? I didn't notice when I was under the hood earlier tonight.
I won't have the opportunity to do the swap until this weekend at the earliest.
__________________ 1999 Merc Grand Marquis
4.6L engine
144K miles
Need it to go another 144k
I am a relative novice to car repair. I've replaced plugs & wires and this year I learned how to replace brakes and did so on three vehicles. It looks like I'll be learning how to replace the exhaust system very soon. "Back in the day" I'd been known to replace radiator or two and a water pump once, but that was before you'd have to take apart the entire front end to do so. (Shoulda kept the '74 Cougar with the 351.)
Do the wires that attach to the top of the coil disconnect easily?
YES
__________________
BroncoJoe19
2006 Alt Fuel Jeep (electric)
'98 windstar 3.8L
'99 Crown Vic 4.6L
'90 Full Size Bronco 5.0L
I'm not a professional mechanic, take my suggestions with a grain of salt, or a cup of coffee
At the bottom of each post there is a little icon
Clicking it gives feedback to the moderators, and poster regarding which posts are most helpful.
One step further. Was there any liquid in any of the spark plug wells ?
While your doing this apply silicon dielectric grease to both sides of the coil-on-plug.
It's very difficult to tell the extent of liquid in the spark plug well. It's not an easy task to get a good look in there. I might take my video camera and try to get a direct shot. The boot is dry on the outside, except for the very bottom. However, when I removed the spark plug, it is wet on top (the half that's outside of the engine).
The heater hose does not *appear* to be the culprit, since it is dry on the outside from the firewall down to whereever it goes.
__________________ 1999 Merc Grand Marquis
4.6L engine
144K miles
Need it to go another 144k
I am a relative novice to car repair. I've replaced plugs & wires and this year I learned how to replace brakes and did so on three vehicles. It looks like I'll be learning how to replace the exhaust system very soon. "Back in the day" I'd been known to replace radiator or two and a water pump once, but that was before you'd have to take apart the entire front end to do so. (Shoulda kept the '74 Cougar with the 351.)
One step further. Was there any liquid in any of the spark plug wells ?
While your doing this apply silicon dielectric grease to both sides of the coil-on-plug.
Thanks phantom_smack and oldwizard!
Yesterday, I finally had the fair weather *and* opportunity to get under the hood and, yes, the spark plug well is wet and, yes, I noticed the coolant heater hose and port right above the well. (BTW, this is the plug closest to the firewall on the passenger side.) As an added bonus, I remembered that I had the cooling system flushed back in December (getting no heat).
So, this morning I took the Marq back to the repair shop that did the flush. Hopefully, they'll resolve it.
__________________ 1999 Merc Grand Marquis
4.6L engine
144K miles
Need it to go another 144k
I am a relative novice to car repair. I've replaced plugs & wires and this year I learned how to replace brakes and did so on three vehicles. It looks like I'll be learning how to replace the exhaust system very soon. "Back in the day" I'd been known to replace radiator or two and a water pump once, but that was before you'd have to take apart the entire front end to do so. (Shoulda kept the '74 Cougar with the 351.)
Just got a call from the shop. They concurred about the coolant leak from the heater hose.
They also confirmed that the coil is not bad. In fact, they wondered how in the world the engine wasn't missing, since the top end of the plug was GONE. The electrode and part of the ceramic insulator! Sure enough, I checked my spark plug socket, and there it was. A clean break down to the first quarter inch of the ceramic insulator. I'd say the coil is working just fine.
I sure don't remember hearing a snap when I tightened that plug in. Can't really see squat down that plug well, so I guess it's a lesson that I need to do a finger test. And, well, yeah, check the socket.
__________________ 1999 Merc Grand Marquis
4.6L engine
144K miles
Need it to go another 144k
I am a relative novice to car repair. I've replaced plugs & wires and this year I learned how to replace brakes and did so on three vehicles. It looks like I'll be learning how to replace the exhaust system very soon. "Back in the day" I'd been known to replace radiator or two and a water pump once, but that was before you'd have to take apart the entire front end to do so. (Shoulda kept the '74 Cougar with the 351.)
Shopping for new Ford can be a stressful experience especially if you don't have the right information. Our new car research center at CarEverything.com can help relieve this stress and bring the joy back to new car buying!
The Car Blog, or TCB for those who are acronymically inclined, is alive because some of today's top Web designers needed a place to drool and bitch about their motor vehicle obsessions.
Read the auto blog at Automotive.com to get the latest news and opinions, view the newest concept cars, and join discussions with auto experts from around the world.
New spark plug didn't fix misfire; now what? 
Hybrid Mode
