*SOLVED* 2003 4.6L 4x4. Stutter under load, suspect fuel pump?

[zerodevil]

Hello Ladies and Gents.

I have been working to restore my 2003 explorer to its old glory. A month or so ago I developed a stutter while the vehicle is under load (5th gear exclusively), at low RPM and Highway speed. I gave the old girl a nice tune up (fuel filter, clean air filter, clean MAF, clean IAC, Ford spark plugs, and verified ignition coils in working order on primary and secondary sides) and produced no change. Next I did a compression test and everything checked out fine.

My next step was to do a fuel pressure test, I am getting 22 Psi before starting the truck, and 68 Psi after starting. The first # is below spec for a 2002 manufactured truck, and the 2nd # is above. Leads me to believe i have a failing fuel pressure regulator?

Any advice on this one?

*EDIT* Also forgot to mention truck is fairly modified, and has ~185,000 miles.

 

[boominXplorer]

How did you "check" the ignition coils? I can almost guarantee one is causing your studder, I see this all the time.

 

[zerodevil]

How did you "check" the ignition coils? I can almost guarantee one is causing your studder, I see this all the time.

I used a digital multi meter to check the resistance of the primary and secondary windings of each COP. First by going across the two pins at the top, and ten from the electrode out of the bottom to each pin at the top. All cop's were with in 3% of listed spec from MSD. I did locate one bad cop which was replaced by an identical msd coil.

 

[boominXplorer]

Ignition coils usually cause issues when hot or subject to moisture. If the coil had completely failed then your readings would be off but yours is weak under load. In my shop we have a COP tester that will read the voltage output while the truck is running which usually will find the affected one. If that doesn't work get access to a higher end scanner with power balance or download Forscan and get a compatible cable. That way you can narrow down to a certain cyl without a check engine light code.

 

[zerodevil]

I bought a ODB2 USB cable on amazon which should get here in a few days, and ill do some more digging once it arrives. On a second note i discovered an exhaust leak as a side effect of running some intake valve cleaner through the truck tonight, It didn't smoke long enough for me to locate exactly where its coming from but its up close to the engine on the drivers side to be sure. Could that exhaust leak be throwing off o2 sensors enough to cause issue? Fixing it either way.

 

[zerodevil]

Just spent about 30 minutes out in the truck with FORScan, It does not appear to have a cylinder power balance test built in for my vehicle. Am i doing this wrong or is there another piece of software that you would recommend?

 

[zerodevil]

Got a set of Spectra premium Coils to throw on and see if it solves my issue. Will update when they arrive.

 

[zerodevil]

Installed the Spectra Coils tonight and reset the adaptive memory, and truck is running at 100% again, thank you for the advice!