2006 5.4L Intermittent Dead Miss

[bskouby]

Hey all, I posted this over at F150online, but I thought someone over here might have some insight into this. I am gryphon custom tuned, so there could be something I am missing here. This is what I posted:

------------

I'm having an intermittent issue with my 06 FX4 5.4L that I thought someone might be able to shed some light on. Some background about the truck first.

It is Gryphon tuned (custom 87 performance and tow tunes)
No CAI, stock filter
True duals, no mufflers, maggie X pipe, stock cats
47,000 miles
plugs changed around 44,000 with replacement motorcrafts (SP507 I think, but I cannot remember right off the top of my head).
new motorcraft COPs

Last spring/summer I started noticing a hesitation/lugging/slight miss at about 45-50 MPH. This issue NEVER threw a CEL or stored a code. This issue would repeat in stock tunes, canned tunes, and gryphon custom tunes. After doing some research on this board, I concluded that I probably had a bad plug and/or COP. Since I had no idea what cylinder the "misfire" occurred on, I just figured it was best to replace the plugs and COPs.

I ended up breaking off two plugs (cylinders 1 and 8) but was able to extract using the Lisle tool. The plugs looked OK. After putting the truck back together, everything ran great. That is, until recently.

For the last few weeks, the truck would intermittently start having a "dead miss". This normally occurs when the truck is at full operating temperature. Sometimes it will happen at speed, sometimes it will happen when idling at full stop. Many times when the miss starts, I can lift off the accelerator and get back on it to clear the issue. Sometimes it will continue to miss until I shut the truck down and restart.

My first though was the tunes. I reset back to stock and ran a couple tanks of gas through. No issues. I then switched back to tranny tune only, and ran for a while. No issues. I then loaded up the performance tune, which behaved for some time (probably at least 300 miles) and then it started missing intermittently again. I loaded the custom tow tune, same issue.

Even though the problem shows up when tunes are loaded, I don't think it is a problem with the tunes themselves. I *think* I still have a problem with either plugs, COPs, or injectors. I also think that the tune is just aggressive enough on timing or fuel/air to make this problem surface.

I'm still not getting a CEL or a stored code when this is happening, so I cannot narrow it down to a cylinder or bank. The only thing I haven't tried is loading the canned tunes. I'm not sure this is really necessary, but for testing purposes I probably should.

Any ideas what to look for? Should I pull the plugs one by one and check them out? Could we be looking at an injector sticking closed? What I find weird is that I can drive for literal days and weeks without any bad behavior, and then one day I have several instances in a single day.

And it is a true miss. The exhaust note gets real flat, truck starts to shake. Oh...and finally....the fuel economy completely sucks. However, the fuel economy always sucked on this truck, and it is winter here.

Any insight would be appreciated. This truck runs like a raped ape 98% of the time. It is just the other 2% that is really annoying me.

Thanks!

----------

Also, I pulled and cleaned my MAF using the CRC electrical contact cleaner spray this past weekend. I did notice that there was a bit of a clear oil like substance all over the MAF housing. I do not run an oil impregnated filter, but it is possible the previous owner did though (I bought it used at about 30K).

I also replaced the fuel filter. The filter looked original, and the fuel I poured out of the filter was slightly darker than normal, but not bad overall.

The truck does run/idle smoother than before, but it did not correct the "dead miss" issue. I still don't get a CEL, so I cannot narrow it down to a cylinder or bank. I'm planning on pulling the COPs and plugs this coming weekend and see if I can spot anything out of the ordinary.

The issue still only surfaces when under tune. If I run stock or the tranny only tune, it will not miss. This still leads me to believe that there is a weak point somewhere, and the tune is pushing it over the limit. I am going to check for a cracked insulator on my plugs, and take a close look at the COPs. I am running motorcraft COPs, and I have the 8 original COPs sitting on my work bench.

The miss does seem to start under load at right around 45 when the truck shifts into OD. This is why I originally changed the plugs and COPs earlier to address this issue. However, the issue has worsened now and will miss even at idle (however, it has never to my knowledge started missing at idle, it is usually after missing at load first).

Any other thoughts out there? Anything I can look for this coming weekend? I'm also leaning towards an intermittent injector fault, but not sure how I can check for that.