Car misfire, then coil pack smoked and then car died

[Betsy98Sport]

I was leaving work when I noticed the 98 Explorer 4.0 OHV Sport started to misfire. So I pulled over and looked over the engine for a few minutes. Minutes later while the engine was running, I noticed smoke coming from engine area and it smelled like burning plastic. Soon after that the engine quit. I tried to start it again and it turned over just fine but would not start. I look over the engine again and noticed melted plastic right next to the coil pack.
After getting home by tow, I pulled the coil pack off and sure enough the coil pack had melted out of the bottom and hardened plastic was sitting there on the intake manifold from it oozing out of the coil pack. I also looked at the fuses and noticed that #17 and #19 on the driver side fuse panel were blown. I don't think #17 was related. That may have blown some other time and I didn't notice but it may happened this time. I wasn't able to read codes until replacing #17 fuse however.
So I thought for sure, it the coil pack. I bought a new one and put it in. The car ran great for a 2-3 minutes and then started to misfire again. I turn the engine off but left the key on. Sure enough 2 minutes later the coil pack over heated, smoked, and oozed out from the inside. Same issue again and #19 fuse blew out again. And it threw the code P0352
And by the way, I've never had to replace the coil pack before. The one in the car is the original one.
Any help would be appreciated? Here are some pictures of the new coil pack after overheating and melting. The original coil pack looked the same.

Here's the part where it oozed out. That's hardened so I assume it was plastic that melted out from the inside.

 

[Runnin'OnEmpty]

Check the plug wires; I'll bet you have at least one that's
open with no connection to the spark plugs. When this happens,
there's no outlet for the secondary voltage and the coil overheats
and shorts internally.

Plug wires should have about 8-12K ohms of resistance per foot
of wire.

 

[Betsy98Sport]

The plugs are under a lifetime warranty and I've had them for probably 6-7 years so I'll go get them replaced today.

The new coil pack was on a lifetime warranty too so hopefully they'll take that back as well.

 

[Betsy98Sport]

What should I test for when it comes to voltage, resistance, etc.? before I hook a new coil pack because I don't want to fry the next one too. They might not honor a third replacement.

 

[boominXplorer]

Like others have said I would inspect the plug wires carefully or replace. Might have a plug wire that has rubbed against something and grounding itself out.

 

[shadowless127]

I would investigate the plug/wire that connects to the post closest to where it's oozing; since that is theoretically the hottest part.

 

[Betsy98Sport]

I put in brand new wires and another new coil (under warranty). I checked the gaps on the plugs. They're all good. I replaced those plugs not too long ago so they are in good shape.

It did the same thing. Fired up good for about 2 minutes and started to misfire. I haven't pulled off the coil pack but I could smell that it had melted.

Any ideas? Anyone? Is there a process I can do to narrow down the problem?

 

[e200e]

You've probably already seen this but here you go http://www.obd-codes.com/p0352.

 

[1998Exp]

Sounds like the PCM-driven end of the primary side of the coil which fails repeatedly is shorted to ground. You can check this by identifying the proper wire and hooking a test light from that point to +12V (battery). When cranking the engine (with fuel pump inertia switch tripped) you should see the light blinking. A steady on would indicate a short to ground. To confirm and diagnose further, disconnect the harness at both ends (PCM and coil pack) and measure resistance to ground. If you find a short, look for something like a support bracket poking through the harness insulation. If no short to ground found, you may have a bad PCM that's frying your coil -- not common, but it happens.

I put in brand new wires and another new coil (under warranty). I checked the gaps on the plugs. They're all good. I replaced those plugs not too long ago so they are in good shape.

It did the same thing. Fired up good for about 2 minutes and started to misfire. I haven't pulled off the coil pack but I could smell that it had melted.

Any ideas? Anyone? Is there a process I can do to narrow down the problem?

 

[Betsy98Sport]

When I said I checked he plugs I only checked the plugs associated with the blown coil (3 an 4). But yesterday I checked all of them. #1 was covered in soot and had oil on the threads. 1, 2, 4, and 5 both had some oil on the threads. And after checking the gaps they were in specs except for #4 . However half were at .52 and some at .56.

I suspect the oil maybe from a leaky valve cover gasket however.

 

[Runnin'OnEmpty]

When I said I checked he plugs I only checked the plugs associated with the blown coil (3 an 4). But yesterday I checked all of them. #1 was covered in soot and had oil on the threads. 1, 2, 4, and 5 both had some oil on the threads. And after checking the gaps they were in specs except for #4 . However half were at .52 and some at .56.

I suspect the oil maybe from a leaky valve cover gasket however.

Those plug gaps aren't large enough to cause your repeated
coil failures.

The code P0352 reads: Ignition coil B primary circuit malfunction. The fuses you're blowing are 17(cigar lighter) and 19(PCM power diode).

You definitely have a short in the coil primary circuit somewhere. There's also a radio static supressor connected to the coil circuit that could short to ground. I'd disconnect
it first and do some testing with an ohmmeter. The problem could be the PCM diode, relay, static supressor, or related wiring and plug-ins....or as was stated the PCM itself.

Did fuse 17 blow again along with fuse 19, after you replaced the coil?

 

[Betsy98Sport]

Those plug gaps aren't large enough to cause your repeated
coil failures.

The code P0352 reads: Ignition coil B primary circuit malfunction. The fuses you're blowing are 17(cigar lighter) and 19(PCM power diode).

You definitely have a short in the coil primary circuit somewhere. There's also a radio static supressor connected to the coil circuit that could short to ground. I'd disconnect
it first and do some testing with an ohmmeter. The problem could be the PCM diode, relay, static supressor, or related wiring and plug-ins....or as was stated the PCM itself.

Did fuse 17 blow again along with fuse 19, after you replaced the coil?

No. I think #17 blew a while ago. It has not blown since

 

[Betsy98Sport]

So I hooked everything back up again to see if I could isolate the issue and repeat fuse #19 being blown again. Before, everytime I replaced fuse #19 and then turn the key on, it would blow within a minute.

I placed the original blown coil with plug wires attached. I put the old plugs back in as well. I disconnected the following: fuse #19 , PCM diode, PCM relay, coil pack connector, and radio suppressor.

I replaced each item in the same order as listed above with key on. First the #19 fuse, then the PCM diode, relay, etc. After eventually having everything connected, fuse #19 was still intact. I can't repeat the blowing of fuse #19 . Now this is frustrating. The only I noticed was that the battery was bit lower than spec. It was at 12.2V. Maybe there wasn't enough voltage when performing the test.

I started the car with the original blown coil pack. It was misfiring as expected but still no blown fuse #19 .

Any ideas what to do next?

 

[Runnin'OnEmpty]

Reread post #9 by 1998Exp; he's probably on the right track. The test he describes is your best bet at this point.

There must be a short in the wiring going from the coil plug-in to the PCM, to generate that much heat. Might examine the PCM plug-in closely for any bent pins, corrosion, etc. There'll be 3 wires going to the PCM that grounds out to fire the coil pairs. The only wiring diagram I have is for a 4.0 Ranger, and it shows the pin numbers as being 26, 52, and 78 on the PCM plug. That might not be
correct for your application??? Wire colors might be tan with white, orange and light blue stripes???

PS: The #19 fuse isn't blowing because the circuit has burnt open in the old coil. If you installed a new coil it would probably blow again...

 

[Betsy98Sport]

Reread post #9 by 1998Exp; he's probably on the right track. The test he describes is your best bet at this point.

There must be a short in the wiring going from the coil plug-in to the PCM, to generate that much heat. Might examine the PCM plug-in closely for any bent pins, corrosion, etc. There'll be 3 wires going to the PCM that grounds out to fire the coil pairs. The only wiring diagram I have is for a 4.0 Ranger, and it shows the pin numbers as being 26, 52, and 78 on the PCM plug. That might not be
correct for your application??? Wire colors might be tan with white, orange and light blue stripes???

PS: The [URL=http://www.explorerforum.com/forums/usertag.php?do=list&action=hash&hash=19]#19 [/URL] fuse isn't blowing because the circuit has burnt open in the old coil. If you installed a new coil it would probably blow again...

I know which wires your talking about. Yes, the wires are the same at those pins 26, 52 and 78. I examined the PCM plug and pins before. They look good. No corrosion or bent. I tested for continuity and they were all the same. Not sure if there's standard specs on the resistance from coil plug to PCM connector.

Makes sense now why I couldn't recreate the blown fuse at #19 . Also I ran the engine (I know its not the best call) because I had to move it for street sweeping. It had the obvious misfire but didn't blow fuses or die.

 

[Betsy98Sport]

Sounds like the PCM-driven end of the primary side of the coil which fails repeatedly is shorted to ground. You can check this by identifying the proper wire and hooking a test light from that point to +12V (battery). When cranking the engine (with fuel pump inertia switch tripped) you should see the light blinking. A steady on would indicate a short to ground. To confirm and diagnose further, disconnect the harness at both ends (PCM and coil pack) and measure resistance to ground. If you find a short, look for something like a support bracket poking through the harness insulation. If no short to ground found, you may have a bad PCM that's frying your coil -- not common, but it happens.

I will try this test tomorrow. Just so I test this right, I have a question. When I hook up the test light, are you saying go from the coil pack connector to the battery? If so, do I place it on the positive or negative terminal? I don't want to fry the PCM. I don't want to mess up here and kill a good PCM.

I'm not sure how to do the second test. Am I measuring PCM pins to ground to check for short any possible short in the PCM to coil pack wires?

 

[Runnin'OnEmpty]

Maybe this will help some: When examining my 2000 today, the positive wire on the coil plug-in is red/lt green. It's on the end of the plug. The other 3 are the coil trigger wires. You can use the red/lt green wire for the positive source, and connect the test light between it and one of the
other 3 trigger wires. Then crank the engine with the FP relay removed, and observe the light. It should blink if the PCM is working properly. Test all 3 trigger wires.

However, this might not tell you much if the PCM is failing when it gets warm. It's suspicious that the engine runs fine for a few minutes after installing a new coil pack. Sounds like the PCM is giving the correct coil signals for a time, and then grounding out one of the wires completely, causing that section of the coil pack (3&4 ??) to overheat and blow the fuse.

I'm just thinking out loud here, and throwing out a theory so do all the tests you can before replacing the PCM....

 

[1998Exp]

I will try this test tomorrow. Just so I test this right, I have a question. When I hook up the test light, are you saying go from the coil pack connector to the battery? If so, do I place it on the positive or negative terminal? I don't want to fry the PCM. I don't want to mess up here and kill a good PCM.

You won't damage anything by connecting the test light to BAT+. It takes very little current. And, as someone already pointed out, with ignition on, battery voltage is available at the coil connector.

I'm not sure how to do the second test. Am I measuring PCM pins to ground to check for short any possible short in the PCM to coil pack wires?

In case of a short to ground, I tried to advise you how to tell if it's the wire harness or the PCM. If you disconnect the harness at both ends, you can use your meter to check its resistance to ground. If the harness is good, that should be very high. Hope this helps. Good luck!

 

[Betsy98Sport]

Great. Thank you guys. I will try this out tomorrow. Didn't have time to do it today.

 

[Betsy98Sport]

So I ran the test today with the test light on the coil pack connector. I had interesting results. After testing the white/tan and green/tan which seemed normal, the orange/tan wire would glow bright (off timing) and go back to regular blinking. This seemed to show a short here. However, when I tried to repeat the test I couldn't get the same result. Everything seemed normal at this point.

I peeled back the casing for the wires at the PCM end and Coil plug end to look for frays in the wires. Nothing there. I didn't open up the whole harness.

The other I found were some exposed parts to the radio noise capacitor. I noticed there was some electrical tape covering an exposed part near the connector. Also there was a crack in the wire near the tape that was exposed but not covered. You can see where it was exposed in the pics (sorry for bad resolution)


Tape covering exposed part

Frayed part that was covered by electrical tape

Cracked part of wire that was uncovered

What do you guys think?