My 2005 5.4 has been mis-firing under low-load conditions, such as 50-65 MPH in overdrive, for about a month now.

The truck: Original owner 2005 5.4 w/ 80,000 miles, Airaid CAI, Magnaflow cat-back, Gryphon CS w/ custom tunes (87 Custom, 91 Tow, 93 Performace). Otherwise, the truck is stock.

Recent maintenance: All fluids and filters regularly serviced, fuel filter less than 10k ago, cleaned MAF, cleaned TB, dealership installed new plugs in July. No CELs. No DTCs from Gryphon CS.

In researching, sounded like COPs, so I installed a set of MSDs. That somewhat helped the misfiring, but it is still apparent.

I'm out of answers. I sent Bill at PHP an e-mail concerning this about 3 weeks ago, but I know he's got his hands full now.

Anybody have any ideas?

 

Aftermarket performance COPS have a bad reliability rating...

Get them out of there and get a set from uneek or global....they are stores on eBay.

 

I would verify a coil before replacing perfectly good ones myself. Either be patient till the code come up or take it to the dealer for a stress test. Last time i did that it was $75

 

I would take it in myself and have it checked could be an injector the 05's have an injector issue. They gave the injectors an extended 10 year 100k coverage.

 

I installed a set of MSD COPs. I've been using MSD for 10+ years in multiple applications, and have been very satisfied with their quality and reliability. Is there something about the 5.4 that may cause them to fail prematurely? As stated previously, after installing the new COPs, the misfire improved, but is not solved.

 

Supercharging is in the plans for my truck. Not any time soon, though. Could I install new injectors now (in attempt to solve the misfire issue - and maybe rid myself of those loud-a** Ford injectors)? If, for instance, I have a S/C selected that would ultimately require 39# injectors for my (future) application, could those injectors be installed now?

 

Bump.

 

Still the same problems with the misfire described above. Still no CEL or DTCs. Although, I did de-tune to stock, and the misfire could not be re-created. Put in another call to PHP, and another e-mail, and a trouble ticket. Anybody got any ideas?

 

So it stopped when you changed back to stock?

 

Correct. So, that leads me to believe that it is tuner-related. Although, now operating under the "stock" tune may just be masking something else. As stated, I've attempted to contact PHP through every avenue available, and their response is, well...typical. (read: absent)

 

Could be a bad tune, happened to me. I just run the canned now, unless it is a dyno tune or street tune, I'll pass. It's risky since the vehicles are all different

 

Thanks, that's what I'll do until I hear something from PHP.

 

Tried recreating the misfire running in 91 Tow, and it is not present. So it looks like 93 Perf Gryphon tune is what exacerbates the misfire.