2003 5.4L 4x4 - low RPM shudder / hesitation / poor MPG

[Eric M]

Agreed, especially under load. But since it didn't sound like there were codes and given that you have to push the vacuum lines out of the way to check/fill tranny - seemed more likley to me he either knocked off, loose or cracked it when playing
With the tranny. That's how Charlie Sheen got in trouble...

Sent from my SM-N970U using Tapatalk

I agree that I need to go back over the hoses all around the area, considering I also redid the PCV valve recently. I noticed that the EVAP return hose (the longish black one with the little green fixture on the end) is dry and corroded, but not broken. I hope the repair turns out to be something as easy as replacing that...rather than the intake manifold.

 

[jimbosidecar]

I had a nearly identical situation with my 2001 Expy with the 5.4L motor. I had just changed the fluid and filter in the transmission when the miss started only at low RPM. Also fuel mileage dipped below 10mpg. It turned out it was a bad/damaged sparkplug way back at the passenger side rear most plug. And it was a job getting back there to change it out.

 

[CaptOchs]

Thanks for the info. I have scanned it multiple times while driving and have not had a single misfire code or any other code. If a plug was bad, wouldn't a code definitely be thrown? I am almost to the point of bringing it in to have a professional-grade scanner hooked up to it, before disassembling and examining the intake manifold.

Not necessarily. Some readers won't detect faulty coils. I had a shudder/hesitation at low RPM but I felt it around 45-50mph. In my situation I could be doing 50 and take my foot off the gas to decelerate for a red light. Then the light changes green before 40mph when you accelerate again it would shutter and hesitate. If I give it more RPM it would go away. Parts stores wanted $200 for a kit of 8 coils. I decided to gamble on the $35 kit for 8 sold on Amazon. It fixed my issue. I didn't lose any power. I towed a lot with the truck too. They have been in there for at least 3-4 years. They probably come from the same factory as the $200 kit. lol.

 

[hypercardriac]

I haven’t noticed if anyone asked about shifts. When you shift into gear out of park is it smooth or kinda clunky, or during gear changes on the road is smooth or rougher than normal shift? My mind is moving towards torque converter..


Sent from my iPhone using Tapatalk

 

[Eric M]

I had a nearly identical situation with my 2001 Expy with the 5.4L motor. I had just changed the fluid and filter in the transmission when the miss started only at low RPM. Also fuel mileage dipped below 10mpg. It turned out it was a bad/damaged sparkplug way back at the passenger side rear most plug. And it was a job getting back there to change it out.

Interesting. I agree, working back there is no fun. Did it throw a code?

 

[Eric M]

I haven’t noticed if anyone asked about shifts. When you shift into gear out of park is it smooth or kinda clunky, or during gear changes on the road is smooth or rougher than normal shift? My mind is moving towards torque converter..


Sent from my iPhone using Tapatalk

Yeah, that is one possibility I am considering. It actually shifts smoothly, no clunking, no slipping gears. So I can still hope!

Before I face the possibility of tranny work, I am trying to eliminate vacuum leaks as a possibility, thanks to the suggestion of bigdogchrisl.

So, I learned that fuel trims can help diagnose a vacuum leak. While the epoxy is drying on my DIY smoke machine, I have a question about interpreting fuel trim data.

Here is some data, followed by my question:

**First numbers are at idle, second numbers are at 2500 rpm**

short term fuel trim bank 1: 0 to 5.5 // 1.6 to 1.9
short term fuel trim bank 2: .8 to 5.5 // .3 to 4
long term fuel trim bank 1: 7 // -3.1
long term fuel trim bank 2: 2.3 //-4.7

My question is this: given that the long term fuel trim in both banks drops quite a bit, isn't that usually indicative of a vacuum leak?
Also, does the fact that the LTFT is negative in both banks mean anything?

My rig is still not throwing codes.

 

[Eric M]

PROBLEM SOLVED:

Even though I replaced the DPFE a month ago, the problem ended up being the DPFE!

The moral of the story is this: Do not buy a non-Motorcraft DPFE because you will be replacing it within 100-500 miles, probably. You can buy the Motorcraft OEM part on Amazon for $64.

I would stay away from the cheaper options on ebay being advertised as "Genuine Ford" parts. I ordered one, came in a Ford baggie, but it failed, and I suspect it was a counterfeit part. The Motorcraft part should come in a red and white baggie, labeled "Motorcraft."

With these Ford sensors, it seems like you get what you pay for.

If you want to test your DPFE, check out this page:
https://www.ford-trucks.com/how-tos...-are-the-symptoms-of-a-bad-dpfe-sensor-561275

Thanks again for all the troubleshooting help!!

 

[riphip]

Put in link for correct Motorcraft part/purchase for the rest of us please. Thanks!

 

[Eric M]

Put in link for correct Motorcraft part/purchase for the rest of us please. Thanks!

Sorry about that. Here it is:

https://www.amazon.com/Motorcraft-D...eywords=motorcraft+dpfe&qid=1607098449&sr=8-3

 

[riphip]

Thanks Eric, don't need it YET