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engine misfire on my 4.6 with no check engine light

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Old 01-31-2014, 02:10 PM
econoconvert econoconvert is offline
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engine misfire on my 4.6 with no check engine light

Hey guys.
I seem to have developed a misfire in my '01 e150 with the 4.6.
It revs fine park or neutral, but starts stuttering when I power brake it.
It also does the same thing just after take off and around 45mph in top gear with the torque converter locked up. After the initial stutter upon takeoff, it pulls strong with no issues until I cruise at 45 to 50 or so.

Is this a coil/plug thing? Or (my suspicion) a vacuum leak of some sort Since it only happens at a particular set of variables (lower rpm and low vacuum).

Thanks in advance.

Oh, and where is the best place to get coil packs from?
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Old 01-31-2014, 10:58 PM
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You need to have it scanned by a scanner that can read pending codes. It almost takes a complete failure of a coil pack to set off a CEL on the older mod motors. The scanner will tell you which one is misfiring..As far as where to get one, either the dealer or I have gotten them from Napa with no issues..
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Old 02-01-2014, 07:37 AM
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Actually, you need a scanner that can read Mode $06, Test $53 misfire counts, not pending codes. Misfire codes, including "pending", are not posted until the rate of misfire exceeds the calibrated limits.

It's almost always a COP/plug misfire issue.
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Old 02-24-2014, 12:32 PM
twlightning twlightning is offline
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What other things would be on the list to check for this type of condition? Mine happens randomly and flashes the theft light half the time it misfires. All new coils and plugs 3k ago and I pulled them all and tested thier resistance a couple weeks ago. They all are within spec. I am pretty sure its something to do with the motor, b/c it misfires then wakes up and runs great.

I'm not trying to hyjack, it just sounds like we have similar problems and it brings this back up to the top.
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Old 02-24-2014, 02:43 PM
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Resistance checks of coils is pretty close to useless. They will only show up a completely open coil but not one that is causing intermittent misfires.

Since your THEFT light is activating, that suggests that you don't have a misfire, but instead have an intermittent failure for the PCM to receive its operating power, most commonly due to a failing PCM Power Relay or some other problem in the power or ground for the PCM.
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Old 02-24-2014, 03:00 PM
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That’s a good thought. I’ll have to check my grounds. I remember relocating a ground over in that area when I did the body lift. The other thing is (pretty dumb I know) I had to use a welder to remove a broken exhaust stud on the back passenger side (next to the pcm) and forgot to unhook the battery. I have been debating on going to the dealer and having the PCM reflashed. I JUST hate taking it to the dealer.
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Old 02-24-2014, 07:39 PM
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I'd swap the relay if there isn't anything apparent with the ground.
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Old 02-26-2014, 12:35 PM
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I swapped the relay under the hood last night and it still did the same thing this morning on the way to work. I pulled a couple of the firewall grounds and reattached them just to make sure they had good contact. I might pull my extended inner fender out and clean the frame ground tonight. I'm thinking about swapping in one of old coils and moving it to each cylinder. Who knows even though all the new ones tested the same.


Just curious, could this also happen with a fuel problem? I put a new pump and filter on it about 5 thousand miles ago. It’s had this problem for 1500 miles or so.
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Old 03-06-2014, 01:05 PM
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I cleaned more engine grounds, but it still has issues. I'm curios if it’s my newer summit racing coils have anything to do with. I know 98% of people with this type of problem end up finding out its their coils. The only reason I bought those is b/c one of the originals shorted out with water in the plug hole and I wanted to replace all of them at once since I am close to 100k. I thought these would be a little stronger and help fuel efficiency. This trucks drinks the gas.
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