BIGDAWG78

OK guys,

about a month ago I noticed a new issue/sound/problem.... When on the interstate/highway (anytime going 55mph and up) when I go WOT around 3300 rpms the engine starts struggling and makes a noise that sounds like I'm hitting the rev limiter. The CEL flashed a few times but doesnt anymore. I have not taken it to the stealership yet to have their complete diagnostic done. Any ideas here? I have new plugs and COPs so I'm doubting its that. The sound (to me) sounds like it's hitting the rev limiter.

edwin108

Typically, a flashing check engine light means you have a misfire. Does it even out at WOT or does it continue to struggle? Also, when was your fuel filter last replaced?

MGD

Hi.

If yer CEL flashed you likely have some stored codes ( even though the CEL is not currently lit).

Need to get those pulled with a good scanner ( not Autozone, etc).

Proceed from there after you have some data.

good luck


MGD

BIGDAWG78

Thats what i first thought, but had a few buddies in it the other day and after much discussion, it doesn't sound like a misfire.... It really does sound like its hitting the rev limiter.. Its does not even out at all, the truck kind of surges... Fuel filter was replaced less than 5k ago. new motorcraft plugs and ACCEL COPs. It goes in on friday for new VCT solenoids (slight tick from 700-1100 rpms), tranny fluid change and rear/front diff fluid changes too.

My plan was to take it to FORD and have them run their complete ECU diagnostic but I'm trying to get ideas before I go up there...


other ideas from my buddies riding with me--

Exhaust leak or vaccuum leak...

edwin108

I don't really think its a vacuum leak since you have practically no vacuum at WOT. It could also be a fuel pressure problem. Have you checked your FPDM?

BIGDAWG78

ok good to know. I haven't checked my FPDM but I have a new one sitting on my kichen counter going in this friday. I am trying to "knock out" all the known 5.4 issues to insure my truck lasts to 200k+

MGD

Hi.

When you say 'Accel' COPs, I immediately think 'misfire', lol. Those things are notorious for failing at any time. Use only Motorcraft or Visteon COPs for reliability.


The plugs - was fresh dielectric used in the boots (or better yet, dielectric in NEW boots). Applied properly. SP515 plugs, right?

Yer not the first feller to have a fresh plug change and get misfires soon after. The procedure is explicit and attention to all details is crucial - even to the point of not using excessive nickel anti-sieze on the ground shields - as that can migrate down and foul the plugs.

Exhaust/vac leak won't cause a flashing CEL , AFAIK. You'd typically get a hard code instead.

The codes are key - need those as Job#1.

EDIT - just saw Edwin's post after typing this - very good point! I hate those things, lol!

good luck

MGD

BIGDAWG78

bump-- for more input to cover all my bases