5.4 stumbling
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5th Wheeling
Joined: Sep 2010
Posts: 46
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5.4 stumbling
99 f150 4x4 5.4
Truck stumbles or misses mostly under a load and around 2000 rpm but lately has been at idle as well. I put a new TPS
on it yesterday and it actually ran good for the test drive (about 2 miles) and when I started this morning it was OK for a couple miles and going uphill, pretty much same problem again. If I turn off the overdrive it helps but that doesn't fix the idle problem. The truck shows no CEL and no codes are present when I check either. Not ruling out coil over plugs but those are less than a year old and when they went out they did set a code. Any ideas what to try next?
Truck stumbles or misses mostly under a load and around 2000 rpm but lately has been at idle as well. I put a new TPS
on it yesterday and it actually ran good for the test drive (about 2 miles) and when I started this morning it was OK for a couple miles and going uphill, pretty much same problem again. If I turn off the overdrive it helps but that doesn't fix the idle problem. The truck shows no CEL and no codes are present when I check either. Not ruling out coil over plugs but those are less than a year old and when they went out they did set a code. Any ideas what to try next?
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
Classic faulty coil that does not set a code.
Why; it comes and goes during operation so is cancelled often.
Which coil?
Best way is put a Scanner on and look at mode 6, test 53.
At this location in the program is the misfire records for all 8 cylinders.
The one with the highest count is the cylinder.
Change to coil on that cylinder.
Good luck.
Why; it comes and goes during operation so is cancelled often.
Which coil?
Best way is put a Scanner on and look at mode 6, test 53.
At this location in the program is the misfire records for all 8 cylinders.
The one with the highest count is the cylinder.
Change to coil on that cylinder.
Good luck.
Thread Starter
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5th Wheeling
Joined: Sep 2010
Posts: 46
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Thanks for the reply. By scanner I assume you are referring to something other than my HF code scanner. My scanner won't do that. Do I need to take it to a shop to do that, or buy a better scanner?
Never mind Found the answer to that. I need a better scanner.
Never mind Found the answer to that. I need a better scanner.
Fleet Owner
Joined: Apr 2008
Posts: 24,323
Likes: 5,133
From: 0,0,1
Bingo, the scanner needs to be able to read live data and you'll be able to see exactly which cylinder is misfiring.
Laughing Gas
Joined: Jan 2006
Posts: 1,098
Likes: 11
From: Minnesota
If I have a light miss that will not trip a CEL, I'll get the truck warmed up and get it into OD and lug it just enough so it stays in OD. She starts to go lean and the mis-fire gets worse and sets a code for me. It's always a bad COP or better than half the time a dirty contact on the coil where the spring slides on. I bet a lot of COPS are changed due to spring/boot issues.
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5th Wheeling
Joined: Sep 2010
Posts: 46
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My scanner will read live data but most of the time it just locks up and won't do anything. I stopped at Auto zone on the way home and their code reader found a misfire on cylinder 1. My HF Cen-tech doesn't find it though. I got a new motorcraft coil ordered and I'll put that in this weekend plus check the plug.
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5th Wheeling
Joined: Sep 2010
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I'm changing the cop this weekend in #1. I'll give that spring and the boot a good look first. Thanks😀
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Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
Your new coil should come with a new boot and inner spring.
You will see a carbon slug inside the spring.
It is their to inhibit the spring coil winding from generating radio type interference to other circuits due to being pulsed on and off for ignition by producing very high voltage spikes...
Remove the old coil, grease up the new boot tip with the special Grease and pay attention with light grip on the coil so you can feel when the Boot settles down over the plug tip.
You cannot see this so you have to feel it.
The Grease also make it easy for the Boot to slide onto the plug tip instead of jamming off to the side.
Good luck,.
You will see a carbon slug inside the spring.
It is their to inhibit the spring coil winding from generating radio type interference to other circuits due to being pulsed on and off for ignition by producing very high voltage spikes...
Remove the old coil, grease up the new boot tip with the special Grease and pay attention with light grip on the coil so you can feel when the Boot settles down over the plug tip.
You cannot see this so you have to feel it.
The Grease also make it easy for the Boot to slide onto the plug tip instead of jamming off to the side.
Good luck,.
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Hotshot
Joined: Jul 2005
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my scanner will read codes and do freeze frame data... I don't think it will do this "mode 6" test........ What scanners do you guys that do more than "read codes" use ? ................. mine is probably 10 years old and cost $100. back then.
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
My Scanner is getting old now but was from SEARS.
It's hard to tell what a Scanner will do without looking in the user manual.
The outside of the box is a long way from indicating all functions..
Thee mid level and up should do mode 6.
I can also set up freeze frame trap that catches the cylinder # misfire and seems to be the same as mode 6 history indication when a misfire occurs.
My freeze frame can be set to include trap data before or after the event, which ever way you think will tell what you want to see.
It's hard to tell what a Scanner will do without looking in the user manual.
The outside of the box is a long way from indicating all functions..
Thee mid level and up should do mode 6.
I can also set up freeze frame trap that catches the cylinder # misfire and seems to be the same as mode 6 history indication when a misfire occurs.
My freeze frame can be set to include trap data before or after the event, which ever way you think will tell what you want to see.
Cross-Country
Joined: Feb 2006
Posts: 82
Likes: 2
I just had this same problem and couldn't isolate it because when it had sent a code it was for #8 cylinder. Since the misfire had reared up again I assumed it was on that same cylinder... I was wrong. A local shop used their live scan tool to see it was #3 this time and changed the coil and plug for me and she is fixed. Mine had your exact symptoms, misfire escpecially noticeable at lower rpm when climbing even the slightest grades. If you have the patience and an extra coil you could swap them around until you find one with a crack or get lucky and replace the one thats going bad.
Good luck.
Good luck.
Laughing Gas
Joined: Jan 2006
Posts: 1,098
Likes: 11
From: Minnesota
I had a 98 that didn't like coils on #3. I had an 02 that blew the plug out of #3. My current 03 had a bad COP on #3. No truck had a heater hose leak or a wiper nozzle leak. #3 plug seems to loosen faster than the others....,weird.
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