Will bad coil pack throw code?
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From: Indiana
Will bad coil pack throw code?
I don't know if this the right section for this question.
Will a failing coil pack always make the check engine light come on?
I have what feels like could be a failing coil pack, nut no check engine light.
Had codes checked at Advanced Auto, nothing.
2000 Superduty with the 5.4. Still has 4 OEM coil packs on it. Is there much of a way to test them at home? But could be one of the replacements too.
Spark plugs are new. Plugs all appeared to be firing, but some looked cleaner than others. Brownish deposits.
Thanks
Will a failing coil pack always make the check engine light come on?
I have what feels like could be a failing coil pack, nut no check engine light.
Had codes checked at Advanced Auto, nothing.
2000 Superduty with the 5.4. Still has 4 OEM coil packs on it. Is there much of a way to test them at home? But could be one of the replacements too.
Spark plugs are new. Plugs all appeared to be firing, but some looked cleaner than others. Brownish deposits.
Thanks
Post Fiend
Joined: May 2006
Posts: 10,007
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From: Central Florida
Actually no.
The only time it seems to throw a code is if/when the miss count gets high enough. I had one fail and another on it's way out and I only got a light when I couldn't accell past 35mph. The PCM does have codes for misses, P0300 thru P0308 with P0300 being general (which is what I got when I had a code) and P0301-8 indicates the cylinder that is missing.
Coil have an inductive property and most people will tell you that you can't check them with a DMM. However, if it's completely shorted, I suspect a dmm will show no ohm or continuity. I also believe they would all be in the same basic resistance range and any out of range would probably be bad. The only supported test is to move them around and see if the miss changes, but you need good software that can display misses on each cylinder if the coil isn't completely shot.
The only time it seems to throw a code is if/when the miss count gets high enough. I had one fail and another on it's way out and I only got a light when I couldn't accell past 35mph. The PCM does have codes for misses, P0300 thru P0308 with P0300 being general (which is what I got when I had a code) and P0301-8 indicates the cylinder that is missing.
Coil have an inductive property and most people will tell you that you can't check them with a DMM. However, if it's completely shorted, I suspect a dmm will show no ohm or continuity. I also believe they would all be in the same basic resistance range and any out of range would probably be bad. The only supported test is to move them around and see if the miss changes, but you need good software that can display misses on each cylinder if the coil isn't completely shot.
Post Fiend
Joined: May 2006
Posts: 10,007
Likes: 4
From: Central Florida
The EM field in the coil collapses when the ground is disconnected, which is what creates the voltage for the spark. With out an EM sniffer, there really isn't a way to for the PCM to check that it's firing unless it's completely shorted and pulls no current (my guess anyway.)
A neat trick is the ECM can tell which cylinder is not firing by the changes in velocity on the CPS. The crank shaft should increase in velocity very slightly when the cylinder fires, if it's a cylinder's turn to fire off and the velocity continues to slow, the ECM knows it didn't fire. Then if you compare the injector firing and the air velocity against the miss, this should give you an idea that the coil is not firing. The basic premise of it's either air, fire or gas not working.
A neat trick is the ECM can tell which cylinder is not firing by the changes in velocity on the CPS. The crank shaft should increase in velocity very slightly when the cylinder fires, if it's a cylinder's turn to fire off and the velocity continues to slow, the ECM knows it didn't fire. Then if you compare the injector firing and the air velocity against the miss, this should give you an idea that the coil is not firing. The basic premise of it's either air, fire or gas not working.
Senior User
Joined: Oct 2005
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From: NW NJ
It depends on the scanner/reader that you are using. Cheaper ones will not pick up "pending" codes, which is what you have if you have an intermittent or light-load miss.
My local Advance does use a Actron scanner model that picks up pending codes. But, I know from borrowing ball joint presses at Advance, that different locations have different tools. Just have to look at the tool's instructions.
Good luck.
My local Advance does use a Actron scanner model that picks up pending codes. But, I know from borrowing ball joint presses at Advance, that different locations have different tools. Just have to look at the tool's instructions.
Good luck.
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From: Indiana
I do believe I saw Actron on the unit. It was a small handheld device.
The missing is intermittent. And sometimes I do notice it more under a load.
To begin with I was not sure if it was torque converter shudder. But I did not know if that was still an issue with the newer truck. My 95 F-150 had it.
Would reading my plugs tell me something about the possible cylinders that are laying out occasionally. Some were more fouled looking than others, brown deposits.
Thanks
The missing is intermittent. And sometimes I do notice it more under a load.
To begin with I was not sure if it was torque converter shudder. But I did not know if that was still an issue with the newer truck. My 95 F-150 had it.
Would reading my plugs tell me something about the possible cylinders that are laying out occasionally. Some were more fouled looking than others, brown deposits.
Thanks
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Even if it did set a pending code, it would show up as "excessive misfire" on whatever cylinder. It actually doesn't even tell you that there was a COP problem unless the COP electrically fails.
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Posting Guru
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From: Indiana
My COP's appear to be mixed, with still 4 OEM ones. I will probably just grab a full set and replace them all at once.
I now have found a water leak on the crossover water jacket on the front of the intake manifold, so I will probably adress both issues at once.
I now have found a water leak on the crossover water jacket on the front of the intake manifold, so I will probably adress both issues at once.
Senior User
Joined: Oct 2005
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From: NW NJ
It will most likely not set a "pending" code. It either works, or doesn't work. If it is intermittent, the ECM see's it as a working coil. Only when the coil totally fails is when any code is set. I have a ford enhanced scanner and I have had nine C.O.Ps fail over the years. Never once has it set a pending code. I always had to use the trial and error method to find the bad one except for one that totally failed and set a code. I'll be damned if I'm going to pay a dealer $50-$100 to plug in his scanner to read the misfire counters.
Even if it did set a pending code, it would show up as "excessive misfire" on whatever cylinder. It actually doesn't even tell you that there was a COP problem unless the COP electrically fails.
Even if it did set a pending code, it would show up as "excessive misfire" on whatever cylinder. It actually doesn't even tell you that there was a COP problem unless the COP electrically fails.
I've never had to do trial-and-error to find the offending cylinder.
If you are saying that the code does not *explicitly* state that the coil is bad .... that is true. But that is the case for many codes .... they indicate the *result* of a failing component or system. Then we use our brain, experience, advice .... to do the repair.
Thats what I think anyway.
