same ol same ol- 4.6 misfire
New User
Joined: Aug 2006
Posts: 6
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From: northern ca
FWIW...
I've been getting a P0304 (misfire in #4) code from my '97 F150 4.6 (177,000 miles) after episodes of missing & bucking under load which gets worse with heavier acceleration. I discovered that my spark plug was arcing across the ceramic insulator and there was rust on the base of the plug and insulator (?). Replaced the plug & problem reappeared within a few hundred miles. Taped a Q-tip to a wire and swabbed around the base of the spark plug and came back with antifreeze residue!!! (can't mistake that smell). I suspect that the aluminum head has corroded through & I have a pinhole leak/crack somewhere in the hole where the plug goes in. Bizarre.
Is this a known problem? Anybody else noticed this?
I've been getting a P0304 (misfire in #4) code from my '97 F150 4.6 (177,000 miles) after episodes of missing & bucking under load which gets worse with heavier acceleration. I discovered that my spark plug was arcing across the ceramic insulator and there was rust on the base of the plug and insulator (?). Replaced the plug & problem reappeared within a few hundred miles. Taped a Q-tip to a wire and swabbed around the base of the spark plug and came back with antifreeze residue!!! (can't mistake that smell). I suspect that the aluminum head has corroded through & I have a pinhole leak/crack somewhere in the hole where the plug goes in. Bizarre.
Is this a known problem? Anybody else noticed this?
Last edited by k54frog; Feb 5, 2008 at 02:25 AM. Reason: add info
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Joined: Feb 2007
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Dank, sorry to hear that your still having issues. Did you ever replace the coil packs, or atleast check them.
To check the primary resistance of the coil, connect the probes of an Ohmmeter to the + terminal and each - tremianl of the coil. The resistance should be the same for each one. 4.6 engins........ 7/4, 8/2, 1/6, adn 3/5.
To check the secondary resistance, connect the OHM
between the secondary terminals(the one that the spark plug wires connect to) of each coil pack. If the resistance doesnt match, replace the coil packs.
Primary resistance should be 0.3 to 1.0 ohms
Secondary resistance should be 6.5 to 11.5 K-ohms.
To check the primary resistance of the coil, connect the probes of an Ohmmeter to the + terminal and each - tremianl of the coil. The resistance should be the same for each one. 4.6 engins........ 7/4, 8/2, 1/6, adn 3/5.
To check the secondary resistance, connect the OHM
between the secondary terminals(the one that the spark plug wires connect to) of each coil pack. If the resistance doesnt match, replace the coil packs.
Primary resistance should be 0.3 to 1.0 ohms
Secondary resistance should be 6.5 to 11.5 K-ohms.
Posting Guru
Joined: Oct 2005
Posts: 2,209
Likes: 1
From: Louisville, Kentucky
Originally Posted by k54frog
FWIW...
I've been getting a P0304 (misfire in #4) code from my '97 F150 4.6 (177,000 miles) after episodes of missing & bucking under load which gets worse with heavier acceleration. I discovered that my spark plug was arcing across the ceramic insulator and there was rust on the base of the plug and insulator (?). Replaced the plug & problem reappeared within a few hundred miles. Taped a Q-tip to a wire and swabbed around the base of the spark plug and came back with antifreeze residue!!! (can't mistake that smell). I suspect that the aluminum head has corroded through & I have a pinhole leak/crack somewhere in the hole where the plug goes in. Bizarre.
Is this a known problem? Anybody else noticed this?
I've been getting a P0304 (misfire in #4) code from my '97 F150 4.6 (177,000 miles) after episodes of missing & bucking under load which gets worse with heavier acceleration. I discovered that my spark plug was arcing across the ceramic insulator and there was rust on the base of the plug and insulator (?). Replaced the plug & problem reappeared within a few hundred miles. Taped a Q-tip to a wire and swabbed around the base of the spark plug and came back with antifreeze residue!!! (can't mistake that smell). I suspect that the aluminum head has corroded through & I have a pinhole leak/crack somewhere in the hole where the plug goes in. Bizarre.
Is this a known problem? Anybody else noticed this?
Posting Guru
Joined: Dec 2001
Posts: 2,017
Likes: 2
From: Southeast FLA
On the truck in my sig i've dealt with misfires. I had changed out both coil towers in trying to fix it, but that wasn't it...
I never could figure them out until I took a chance and GAVE UP on the spark plug wires that the parts stores sell (yes, even the most expensive premium ones), and bought Ford performance wires from Summit Racing. I'm not saying the wires have to be Ford, but I'm gonna suggest that the boot and tip combinations most parts store brands use (and they probably all use the same, mated to "better" or "worse" wires (again, all marginal) are crap.
In fact, in that time I did once buy a better looking set of blue spark plug wires, but one of those allowed the spark to burn a hole through itself... reducing me to using another set of crappy "premium" wires from yet another parts store.
They may be more expensive, but for these modular motors I'm sticking with the Ford wires now. It's nice to have my truck back.
I never could figure them out until I took a chance and GAVE UP on the spark plug wires that the parts stores sell (yes, even the most expensive premium ones), and bought Ford performance wires from Summit Racing. I'm not saying the wires have to be Ford, but I'm gonna suggest that the boot and tip combinations most parts store brands use (and they probably all use the same, mated to "better" or "worse" wires (again, all marginal) are crap.
In fact, in that time I did once buy a better looking set of blue spark plug wires, but one of those allowed the spark to burn a hole through itself... reducing me to using another set of crappy "premium" wires from yet another parts store.
They may be more expensive, but for these modular motors I'm sticking with the Ford wires now. It's nice to have my truck back.
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Junior User
Joined: Jan 2008
Posts: 72
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From: Memphis, TN
Originally Posted by typhus
To check the secondary resistance, connect the OHM
between the secondary terminals(the one that the spark plug wires connect to) of each coil pack. If the resistance doesnt match, replace the coil packs.
Primary resistance should be 0.3 to 1.0 ohms
Secondary resistance should be 6.5 to 11.5 K-ohms.
between the secondary terminals(the one that the spark plug wires connect to) of each coil pack. If the resistance doesnt match, replace the coil packs.
Primary resistance should be 0.3 to 1.0 ohms
Secondary resistance should be 6.5 to 11.5 K-ohms.
Also, what do the pairs of cylinders mean (7/4, 8/2, 1/6, adn 3/5)? Their relavance?
Gamma- the wires I have I bought from Advance, IIRC, but they are OEM Motorcraft wires.
I'll let you guys know what I find.
Thanks again.
Last edited by DanK5; Feb 5, 2008 at 04:08 PM.
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Joined: Aug 2006
Posts: 6
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From: northern ca
Originally Posted by KingRanchMan02
The problem is known and it is not what you think it is. The heater hose is above the number 4 cylinder spark plug well. The heater hose is leaking and dripping coolant down onto the engine where it drains down into the spark plug well and shorts out the plug. Tighten up the hose clamp and your problem will go away. Good luck!
I looked carefully and found evidence (discolorization) of seepage at all the connections for the heater hoses AND fresh drops of a/f on the top of the plug boot. With 177k on the truck, I think I'll have all the hoses replaced. I replaced the plug and cleaned the well thoroughly with Q-tips duct taped to a wire hanger bent to fit down the well. Inspection with a small round mirror & flashlite showed the well to be squeeky clean after wiping & blowing it out with compressed air. Ran fine today on a 45 mile road trip. Now for the acid test...I take it in for it's biennial smog test in the morning
. BTW, I erased the codes and reset the I/M readiness monitor. Now all the monitors have completed their testing except for the catalytic converter. How long / what is the required "Trip drive cycle" to set the catalyst monitor? My $160 2-volume factory repair manual says to look in the 'powertrain control/emission diagnosis manual' (sold separately, of course, for another $160).
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From: Memphis, TN
Don't have an answer for you but I did stumble on a piece of info in the Haynes manual about NOT clearing codes by disconnecting the battery because that forces an internal memory loss in the PCM of what everything was set at and so it will run rough for a period of time until it relearns where everything should be set at.
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Originally Posted by DanK5
So one end of the meter is in the coil pack plug connector, where does the other end go? This weekend I plan on going through all the tests the Haynes manual recommends. I'll start with the coil test first since it/they are most suspicious.
Also, what do the pairs of cylinders mean (7/4, 8/2, 1/6, adn 3/5)? Their relavance?
Gamma- the wires I have I bought from Advance, IIRC, but they are OEM Motorcraft wires.
I'll let you guys know what I find.
Thanks again.
Also, what do the pairs of cylinders mean (7/4, 8/2, 1/6, adn 3/5)? Their relavance?
Gamma- the wires I have I bought from Advance, IIRC, but they are OEM Motorcraft wires.
I'll let you guys know what I find.
Thanks again.
For the primary resistance,, connect the probes to the positive terminal of the coil, and each negative termianl of the coil. The resistance should be the same for each check.
Heres another way that some of the guys in the shop check it...
Ignition Coil Test
- Disconnect the ignition coil output wire.
- Connect a spark plug to the end of the ignition coil output wire which you just disconnected.
- Connect a ground wire to the threaded portion of the spark plug.
- Disconnect the ignition coil ground wire from the negative terminal on the coil (Green Wire).
- Connect one end of a ground wire to the ignition coil negative terminal.
- Turn the ignition switch to the ON position.
- Tap the other end of the ignition coil ground wire jumper on an good grounding point (for example the battery negative terminal) and look for sparks at the spark plug that correspond to the frequency of your tapping of the ground wire.
- If you have a good spark at the spark plug, the ignition coil is good.
- If you don't get a good spark, check for approximately 12 VDC from the coil positive terminal (black wire) to ground with the ignition switch in the ON position. You should also get approximately 12 VDC from the coil negative terminal (Green wire) to ground
In addition to the test above, you may elect to perform an ignition coil resistance check as confirmation of the coil's condition.
- Check the ignition coil primary coil resistance by connecting an ohmmeter between the positive (Black wire) and negative (Green wire) terminals on the coil. The resistance should be 0.4 to 0.6 ohms.
- Check the ignition coil secondary coil resistance by connecting an ohmmeter between the coil output terminal and the ignition coil negative terminal. The resistance should be 5000 to 7200 ohms.
- If that sounds like too much of a headache, just buy two brand new coil packs.
Last edited by typhus; Feb 6, 2008 at 12:49 PM.
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Junior User
Joined: Jan 2008
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From: Memphis, TN
Thanks man, I have these printed out and hopefully once I get into it a little bit I'll understand more of what exactly you're talkin about.
Side question here- So it's ok to fire the engine with all the air intake stuff off- air box, MAS sensor diconnected and the other wire thats plugs into the air tunnel all disconnected?
Side question here- So it's ok to fire the engine with all the air intake stuff off- air box, MAS sensor diconnected and the other wire thats plugs into the air tunnel all disconnected?
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Joined: Aug 2006
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From: northern ca
Originally Posted by justFord1
I have a misfire on the 8th cylinder, and have no automotive knowledge. Can yall please tell me where is the 8th cylinder on a 4.6.
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Junior User
Joined: Jan 2008
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From: Memphis, TN
UPDATE- Had my mechanic bud come by Sat and he checked some things with the scanner; nothin! He brought over a known good coil and we swapped it out and took a drive- still missing. He asked me again what cylinder was the last engine code that came up so we pulled that plug wire off and there was definitely something going on on the side of the boot. Looks to be arcing to the valve cover under load.
Here's the big question- WHAT CAN WE DO TO FURTHER INSULATE OR PREVENT THE WIRE FROM ARCING TO THE COVER? I'm not convinced that buying a new set of wires is necessarily the answer as last time I did this it started missing just a few weeks later. Could I put some type of material in each hole between the plug wire and valve cover? What material could be used? Heater or fuel hose wrapped around the plug boot? I might try that this week and see if it makes a dif.
Here's the big question- WHAT CAN WE DO TO FURTHER INSULATE OR PREVENT THE WIRE FROM ARCING TO THE COVER? I'm not convinced that buying a new set of wires is necessarily the answer as last time I did this it started missing just a few weeks later. Could I put some type of material in each hole between the plug wire and valve cover? What material could be used? Heater or fuel hose wrapped around the plug boot? I might try that this week and see if it makes a dif.