P0304 again and again the spark plug | Ford Explorer Forums - Serious Explorations

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P0304 again and again the spark plug

greasemanicure

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City, State
Burlington, NC
Year, Model & Trim Level
1996 4X4 4R->5R mod
About 15,000 miles ago I corrected a P0304 misfire problem by changing out a NEW spark plug with another one. The new one that failed showed a dead short from the terminal to the shell. The same #4 cylinder dumped the same P0304 code yesterday and again it is a failed spark plug. Only good news is that this one may be the easiest to replace.

My question is: Has anyone else had a particular cylinder have the plug fail repeatedly? What about the cylinder might cause the plug to fail?

Joe
 



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What about the cylinder might cause the plug to fail?

Joe

Worn rings-oil contamination causing fouling-


Head gasket leak-cracked head -coolant contamination fouling, or insulator crack from coolant leak.


Improper fuel ratio-
A leaking injector would foul a plug
A weak injector might cause it to overheat.

I'd probably start with a compression check of all cylinders.
 






Have you replaced coil pack and wires? I don't know win your last tune up was but if long time ago I'd just replace wires/plugs/coil pack.
 






Here's what I found when I pulled and changed the plug. It was wet with gasoline. No evidence of fouling from oil or deposits. No ashen coloration from overheating. The first new plug that failed (Autolite platinum) was a dead short to the shell. This one was not quite dead short but down around 2 ohms electrode to shell and 8 ohms through the plug. New plug showed around the same 8 ohms through the plug but open/high resistance tip to shell. The last one that failed went through an "autopsy" and when I cut the shell off I found a bit of metal sticking out of the porcelain under the shell that showed short to the electrode. I'll cut this one apart to see if it is the same.
 






Oh, forgot to mention that the change of the spark plug fixed the miss.
 






I've replaced my #4 spark plug 2x in less than a year due to a P0304 code. It clears out the code. But I'm curious as to what is causing the code. Closer inspection of the spark plug reveals brown residue on the threads (see pics). I actually have to clean it off with a steel brush just to get it out...not sure if its oil, dirt, coolant, etc. It has the consistency of grime/mud. The actual spark plug looks good except for the threads as depicted on the pics. Any clues? Please help. I surely don't want to get stranded anywhere with a blown engine...was it the lower and upper intake manifold gasket? Please help.

btw, i use Motorcraft sparkplugs...

photostream
 






....Closer inspection of the spark plug reveals brown residue on the threads (see pics). I actually have to clean it off with a steel brush just to get it out...not sure if its oil, dirt, coolant, etc. It has the consistency of grime/mud. .....

That is a lot of crud in the threads. I've never seen that before. I'd have to drop the plug in some red NC clay to have it look like that.

The last #4 plug I changed has some brown grime in the threads, though nothing I can't scrape out with a fingernail. There is a little brown on the collar just above where the plug seats into the head, but it seems to be a bit of rust. Not sure how the grime got into the threads on mine except maybe if it was picked up as I jiggled it out with the plug socket. If it is much volume, I'd believe it would be hard to get into the threads while firmly tightened in the head.

Check out the replaced plug to see if it is open or shorted to the shell. I've had two Autolite plugs go short in less than 18 months. I've taken to carrying a spare plug and a socket wrench for the next time it throws a P0304 on me.
Joe
 
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I had the issue with #3 cylinder, then #4 stared doing the same thing.
Rusty around the plug threads. Plug looked fine, and the burn color looked good also. Close inspection of the insulation of the plug would reveal a hair line crack. Came to the point where I was forced to replace the #3 and #4 plugs about once a month.

Coolant resevoir would slowly go down over a month or so and need to be topped up.

Aftermarket heads fixed the issue for me. Cracked heads.

SOHC's have timing chain issues, and the factory heads on ohv's are crap. Every motor (almost)has its weak spots. A v8 sure would have been nice.
 






Cracked head or bad gasket?

Coolant resevoir would slowly go down over a month or so and need to be topped up.

Aftermarket heads fixed the issue for me. Cracked heads.

just checked the coolant. And indeed, i've been losing some slowly. However, i've read through a couple of posts here that it could be the lower intake manifold gasket that needs to be replaced. I'm assuming the only way to find out if its a cracked head is to physically check out the heads correct? Also, doing a compression check on all the cylinders will confirm that there is indeed a leak but it won't pinpoint me to a cracked head or lower intake manifold gasket leak correct? Thanks.
 






Dono,

if its indeed a cracked head, what parts do I need to buy in addition to an aftermarket cylinder head? (i.e. do i need to replace intake manifold gaskets? torque bolts? etc.). I'm just trying to estimate the total job cost of your recommendation so i can properly budget it. Thank you.
 






Do you want to do both heads, or just 1?
How much of a budget are you on?

install only one head? (Not really recommended, as the new head will have much better valve seating).
How about your motor ticking? It could probably use rockers and push rods. These wear down, increasing slop in the valve train.
Check clearwater cylinder heads for pre-assembled heads.
http://www.cylinder-heads.com/details.cfm?itemid=1878
So, heads ($210.00) each. $420.00
FEL-PRO Part # MS98005T intake gasket kit - $66.79
FEL-PRO Part # 545SD PermaTorque head gaskets 2*29.79= $59.58
FEL-PRO Part # ES72794 head bolts $30.00
SEALED POWER Part # R1092 rocker arm 12*$12.96=$155.52
SEALED POWER Part # RP3332 push rod 12*$4.64=$55.68
Lifters? Good idea, but expensive. I probably wouldnt bother.

So? $800.00 in parts alone. Rockauto will give you 5% disc on the stuff you purchase from them with a discount code on here.
If you only do one head, you will save quite a bit, but....

Hope that gives you a good idea of what you are getting in to.
 






Dono,

Based on some of the posts i've read here, i've got 3 options to fix my cylinder 4 issue that constantly messes up my spark plug- 1) replace my lower intake manifold gaskets, 2) replace my cylinder heads, and 3) do both options.

since option 1 is the cheapest, i'm thinking of trying that one first. What parts/items do I need to buy to accomplish this besides the intake manifold gasket? any help is appreciated. Thanks.

Regards,
Ty
1996 Ford Explorer XLT (179K miles)
 






You just need the upper intake gasket set then.

Worst case, you have spent he $66.00 + shipping + labour to find out thats not the issue. Then, if you need to do your heads, you will be way more confident as to how easy it is. Once you have pulled your lower intake, the heads are easy.

There is a step by step how to. I'll look for it tomorrow. There are pictures, and it really makes things easy.
 












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