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Multiple misfire. Failed Coil pack test.

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Old 01-23-2012, 06:38 PM   #1
EvilTheCat
Lincoln NE
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Multiple misfire. Failed Coil pack test.

I have a '97 4.0L OHV Explorer.
It's been running bad since I bought it.
I have a code reader now, and I keep getting the error codes P0301, P0303, P0305, and P0306 (misfire on cylinders 1,3,5, and 6).
I've got the P0300 (multiple cylinder misfire) a few times also.
Hell, I even got a P0307 once (that's a misfire on the #7 cylinder, but I only have 6).
There is also a P0171 (lean on bank 1), which is probably a result of all the misfiring.

The kid I bought it from said he just had wires and plugs replaced.
The wires do look new and the plugs I pulled on the driver's side look fine too (They're the double platinum, pre-gapped, plugs).

I began to wonder about the coil pack.
I tested it according to the specification I've seen on here and autozone's free online repair manual.
That is, between 0.3 and 1.0 ohms for the connectors on the side (primary)
And, between 6.5K and 11.5K ohms for the three pairs of terminal towers on the top of the coil (secondary).

I realize that the resistance on this image says between 11K and 17K ohms for the secondary test, which is different from what I just stated.
I put it on just to illustrate how to test.
I got the image off another post on this forum here, and am unsure of it's accuracy.

When I perform these tests I get between 2.0 and 2.3 ohms for the side connector, and between 13.7K and 14.2K ohms for the top.
Both of which are above the tolerance.
Could this be causing my multiple misfires?

I will be testing and pulling a coil off my friend's truck tomorrow to see if her's fixes my problem.
Autozone sells one for $80 which is a lot of dough just to see if maybe it'll correct these issues.
Any other ideas?




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Old 01-23-2012, 07:01 PM   #2
sean kane
Arlington Washington
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Sounds like your on the right track. I had one with a similair problem but I didnt know which cylinders were missing because I didnt have the vehicle scanned.

I tested the coil pack first and it tested fine. I then went on to test the ohm readings on the injectors and found #1 injector to be faulty. I went to the junk yard spent $5 on 1 injector and the motor runs like a top.

Seeing how you are having multiple cylinder mis fires I would be likely to suspect the coil pac not an injector.
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Old 01-23-2012, 08:20 PM   #3
EvilTheCat
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I tested the resistances on all the injectors last week when I replaced the upper intake gasket.
All 6 checked out just fine around 15.5 ohms, so I'm hoping that they are all okay.
I didn't apply a voltage to them to see if they made the click sound as instructed here, but now I'm wishing I had.




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Old 01-23-2012, 08:50 PM   #4
EvilTheCat
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You all will think I'm crazy or just stupid for doing this, but I had to see.
I wanted to know if any particular cylinders were causing me problems, so I pulled the plug wires out of the coil.
Yes I did do it while it was running.
Stupid and dangerous I know.
What I found was that there was no change in engine behavior when I pulled the driver side wires one at a time.
However, every plug I pulled on the passenger side made the engine almost die. Does this mean there's something wrong with the right side of the coil?
When I did the upper intake manifold gaskets last week, I didn't keep track of the wire order and had them all in wrong on the driver's side.
Could running it with the incorrect timing foul all 3 plugs on that side?
I'm going to replace them tomorrow also.
I'll be sure follow up when I get to the bottom of this.




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Old 01-24-2012, 07:00 PM   #5
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So I swapped the coil from my friend's explorer since it tested better (it's a 2wd with a fried engine).
The resistance on the side terminals was between 1.5 and 1.9 ohms.
The resistance on the top connectors was between 11.6K and 12.2K ohms.
Both of which were better than mine.

When I did the wire pull test, as describe earlier, I found that only cylinders 5 and 6 had no change to engine behavior when disconnected.
So now the engine wants to die when I pull the number 4 wire, along with the entire passenger side bank.

I cleared the engine codes, which were the same as before, misfire on cylinders 1, 3, 5, and 6.
After driving the 30 miles back home (some highway, gravel, mud, and residential miles), the only codes I had were for cylinders 5 and 6.
I did the wire pull test again and cylinder 4 was still causing the engine to stumble.

I replaced the plugs for those two cylinders.They looked a little dirty, but not too bad.

But the same codes came back just idling in the driveway.
The same results again from the wire pull test.

I've concluded that it must be the coil pack.
I'm going to buy a new one tomorrow after I get paid.
I'll let you know then what happens.




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Old 01-25-2012, 05:32 AM   #6
Torqueranger
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I was reading up that the plug are pre-gapped and did you check the plugs before you installed them ??? I would put motorcraft plugs in and instead of champion plugs.
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Old 01-25-2012, 06:09 AM   #7
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Make sure you look at the coil real closely, the cylinders 4-5-6 are not in order it goes 4-6-5 and the othe rside is 1-2-3




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Old 01-25-2012, 03:10 PM   #8
EvilTheCat
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Quote:
I was reading up that the plug are pre-gapped and did you check the plugs before you installed them ???
I was under the impression that the double platinum ones didn't need it, but I was looking on Autolite's FAQ and they recommend gapping all plugs.
Looks like I'll be pulling them out again.
Quote:
Make sure you look at the coil real closely, the cylinders 4-5-6 are not in order it goes 4-6-5 and the othe rside is 1-2-3
Thanks, but I went through that mess last week.
I know that they are in the correct order now.
Just to clarifiy for others the coil order looks like this

PS....Coil....DS
3......3 4......6
2......2 6......5
1......1 5......4
Front of engine




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Old 01-25-2012, 05:34 PM   #9
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Well torquranger it looks like you were right about the gap.
I pulled the #5 and 6 plugs, they had gaps of .042" and .040" respectively, and both looked good after 50 miles.

The difference in color must be the camera's fault.
To me, they both looked brand new.

I re-gapped them to the manufacturer's specifications of .052".


Unfortunately, the misfire codes P0300, P0305, and P0306 (Multiple misfire, and misfire on cylinder 5 and 6) came back.

I said I was going to buy a new coil pack today when I got paid, but I've already spent the whole check on bills, food and fuel (I'm only getting about 12mpg with this truck).
Next week, I will buy a brand new coil pack, unless I find something else to be the problem.
Please give me any ideas you might have.




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Old 01-25-2012, 06:24 PM   #10
kkjb4x4.0
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I chased that problem for months on my 97,nothing i did seemed to help, Have you done a compression test? I'm thinking it's something internal like a burnt valve or cracked heads or bad headgaskets. Good luck!
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Old 01-25-2012, 09:29 PM   #11
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Ill do a "me 2" on this also. Do a compression check. i had to pull my heads. After they took a trip to the machine shop, they have been fine. No more missfire codes.




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Old 01-26-2012, 10:14 AM   #12
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I suspect the previous owner was chasing the same problem, gave up and sold the truck to you. If you know him it may not hurt to ask if possibly the problem was professionally diagnosed but too expensive for the kid to fix. Does happen.

If you know for sure that the coil needs to be replaced, $80 at autozone is a bit steep. RockAuto has them for new for $42. I've had great service from them in the past. They are a sponsor & have discount codes floating around on the forum.
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Old 01-26-2012, 10:37 AM   #13
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I'd be checking if the injectors are firing. Misfire and lean code points me here. Misfire is almost always triggered from lack of injector pulse.

Could be as simple as a bad wire in the harness.Each injector has a dedicated circuit to the PCM.

As stated, check compression first.

Ea
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Old 01-26-2012, 11:42 AM   #14
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Definitely check for a harness issue,squirrels & mice love to nest under hood and chew harnesses,look for any remnants of nuts and or acorns underhood!




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Old 01-26-2012, 07:18 PM   #15
EvilTheCat
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So I tried to do a compression test on the driver's side (cylinders 4, 5, and 6).
I let the truck idle for about 2 minutes before the test.
It probably should have been longer to get up to operating temperature, but I didn't want to get scalded by the manifold.
I got 10 psi on cylinder 6 (back).
I got 135 psi on cylinder 4 (front).
Finally, 0 psi on cylinder 5 (middle).
That's the order I tested them.
It was kind of a hasty test since it was cold and dark when I got started on it, so I suppose I could have done it improperly.
My Harbor Freight gauge was a pain in the rear to get into the plug holes because of the EGR tube, but it felt like it was seated in each one.
Perhaps I need a different gauge.

Is it even possible to have virtually no compression on 2 cylinders and still have a running engine?
It actually runs fairly well, a bit under powered and kind of shaky, but it'll still bark the tires and go 75 mph.

I'm sure this means the heads need to come off.
A blown gasket, a cracked head or even the block are all potential issues.
I'll be testing the compression again tomorrow, if it's not too cold.
Are there any other tests I can do to see what's going more specifically without pulling the heads?
One thing I can't understand is why the plugs would still look fine if I had a cracked head.
Wouldn't it have oil or coolant leaking into the combustion chamber?




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Old 01-26-2012, 07:38 PM   #16
EvilTheCat
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I just had another thought.
Is it possible that air could be leaking in around the injectors?
I put new o-rings on all of them when I did the upper intake gasket about 2 weeks ago.
Perhaps 2 of them got didn't go in straight.
I had the same 4 misfire codes prior to doing the gasket though.
And why would it go to only 2 misfires after I put in a new (used) coil?
What a mess.




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Old 01-27-2012, 12:16 AM   #17
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Thanks RomeovilleIL for the RockAuto tip.
They're cheaper than AutoZone for everything I looked at, even with shipping.
Here's the link to the discount code.

And an answer to your question, I don't know the kid who sold it to me at all.
I know he was not very mechanically inclined as I had to tell him to turn the screws the other way to get the license plates off.
He was eager to sell it, so I'm guessing he might have known there was something wrong with it.
I was hoping the rough idle was something easy, but it looks like I should have been less eager to get a 4wd again and looked it over better.
Oh well, live and learn.
I love working on trucks almost as much as wheeling them, so however it turns out I'll be happy in the end.

Turdle and FordSuperCenter, I'll be looking into the wiring tomorrow, after doing another compression test.
Fortunately I have seen no signs of critters residing in my truck.
I did have some mice tear the heck out of my project mustang, so I know what they can do.

Thanks to all who've given input.
It's all appreciated.




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Old 01-27-2012, 12:29 AM   #18
sean kane
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If you have 10 psi on #6 and 0 psi on #5 you likely have a head gasket that is blown between combustion chambers.

I had that happen on my 91gt 5.0 mustang. It still ran but was low on power, had a miss to it, and was a little shaky at idle.

Check them again to be sure, but I would bet the head gasket between #5 and #6 combustion chamber is blown.
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Old 01-28-2012, 07:19 PM   #19
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I did a compression test again.
Turns out I did the test just fine the first time.
135 psi cylinder 4.
Maybe 5 psi on cylinder 5 (just barely heard the psst as I released pressure)
Only about 10 psi on cylinder 6.
My goal is to get the heads off tonight and in to the machine shop tomorrow.
Wish me luck.




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Old 01-28-2012, 07:40 PM   #20
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go Evil!
Hope you made out ok. im sure you did it. pretty fast pulling apart. No torque wrench needed, just a lot of unbolting.




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