Hello All,

I picked up an '01 Super Duty with the V10 a couple months ago at a great price to use to pull my camper. Long story short I had a slightly rough idle and hesitates between 1500-2200 rpm. I changed the coil packs today and seems to have made it better but not perfect. Still does the puffy idle and kind of shudders at take off. It's fine on the highway setting cruise etc. It has 190k on it and not sure when the plugs were last done. There's no check engine light just the shudder I mentioned. How bad do the plugs come out? I guess kind of doing a risk reward kind of thing because yes I could live with the way it is if I'm going to pull the threads out of the head by pulling the plugs out. Also could it be a bad injector? This is all new to me as I've had a GMC 1/2 ton the last 13 years til the frame went bye bye. Lol. Any help is appreciated!

 

I've changed plugs twice on our 5.4L 2003 Exped 175k with no issues concerning the threads in the heads, once on the 6.8L Excur with 130k.
The issue with stripping threads in these heads in my opinion is leaving the OEM plugs in for 100k giving them time to work loose.
The OEM torque was low and if a plug worked loose the compression pulses would pound the threads until the plug blew out.
Change plugs and boots at 50k, torque to 25 ft/lbs and you probably won't have any issue.
Almost all the coils on mine are OEM.
The most difficult issue is getting to the plugs on the passenger side with all the stuff in the way.
Check all the vacuum hoses as they are probably starting to show their age.

 

I just changed coil packs and plugs on my 03 in an effort to correct a misfire on #10 cylinder. My engine had the same symptoms you are describing. I've replace my plugs one time before and it wasn't a problem. The worst thing is laying on top of the engine to reach the rear cylinders. I wasn't able to eliminate the misfire with new plugs and coils so I checked compression. 25psi on #10 cylinder. I believe I have a burnt exhaust valve. Not the best news.
Anyone else out there have issues with cyl heads.

 

This could also be a throttle body in need of cleaning. Since you change your own plugs this would be an easy procedure. Here's a nice how-to video from YouTube:
HTH

 

Before you do anything else, clean the MAF and change the fuel filter. Check for vacuum leaks, especially the PCV elbow that's been talked about here a lot.

At 190K if the MAF hasn't been cleaned, it's going to be very ugly

An injector with a bad spray pattern could do this too... does the exhaust ever small like rotten eggs?

 

Second on the MAF and PCV. Easy to check and costs nothing.

 

1) check all injector clips to make sure they are latching on and not loose.
2) check coil clips...assume you did this when new coils were installed. I hope the coils were denso.
3) clean MAF
4) replace all plugs with new
5) check fpr vacuum hose for leaks and proper connection and all other vacuum hoses. Look for gas or heavy gas smell on fpr end of fpr vacuum hose.
6) put a new IAC on
7)replace fuel filter
8) check fuel pressure
9) remove injectors and put refurbished units in
10) check voltage of battery while running. Should be above 13.5v
11) check any pcm codes or misfires with torque pro and record them. Then clear pcm.

do these 1 at a time and stop when/if it is fixed.

if not post back for more steps.
Next phase will be compression tests etc.

 

This maybe should be 13.1-13.6v.
Our 2002 & 2003 usually are 13.4-13.6v right after starting and settle in to 13.1-13.4v after a couple of minutes.
Anything over 12.6v means the alternator is charging, but everything will run fine for 1-2 hours on just the battery.

 

I reordered this by expense (and one or maybe two based on probability) and added a note or two.

I really hate it when people throw parts at a problem, and do not do proper diagnosis and waste a lot of money.