Just bought a 1998 Navigator 5.4L 16 valve - 115k miles.....Central Florida

Here's the history:

1) Ran great for 2 weeks then went up a few hills in north florida and started missing/bucking
2) Changed plugs (8 new Motorcrafts), 8 new COPs and 8 rebuilt injectors (at 115K miles I thought these things were due for a change anyway)

Ran great for 5 miles city test run, parked the Navigator and went for ride 4 hours later, ran worse than day 1 - like it is running on 6-7 cylinders.

3) Checked codes - got P0356 "Fault in ignition" COP #6. Changed #6 COP with old COP and still running on 6-7 cyl. Also noticed exhaust smells like rotten eggs, was not smelling like this before.
4) checked for vaccuum leaks with can of TB cleaner - found none.
5) Also noticed the EVR - (EGR regulator) makes funky noise when engine is stopped (like whining pipes in an old house).

Drove again for 10 miles to force engine to throw code - no results.

Could this be a plugged cat? Bad EGR? Bad COPs?

Anyone have similar issues?

 

Guys,

Here's a few more details:
Filled up tank with 87 octane 1 week ago, thought maybe I got bad gas so I did the most inexpensive thing and put 1 bottle of alcohol into tank so that if there is water in tank it would mix with alcolhol and burn out. Also, partially cleaned throttle body when I changed the plugs/cops/injectors (today). 3 weeks ago when I bought the Nav, I changed oil, tranny fluid and new fuel filter.

 

I am having the exact same issue, except with cyl. #4.
It is driving me CRAZY!

 

(1)If you changed the COP on #6 and your problem still exists you might want to pull the "rebuilt injector and put the one you had in there, back in.
(2) Never mind, I see you changed your fuel filter in your 2nd post.
(3)You need to check your fuel pressure at the schrader valve on you fuel rail. Normally I could give you the spec. but I just looked for my Haynes manual and can't find it. (we have the same engine & year)

Go through these steps 1st and let us know what happens.

TJKinCNY

 

Older Navigators had a problem with the driver's side valve guides in the head. Have to replace cylinder head. The one I did at work had low compression. Remove the plugs and do a compression test.

 

Right! Or the rockers fell off, - that happens as well, check rockers first after it fails a compression test.

 

I will be swapping out the #6 injector and #6 COP again shortly and will post results.

 

I pulled out the low voltage connectors on the COPs one-by-one and found #7 was not firing. I swapped out #7 COP and it is running much better. The engine don't sound quite right to me. Do the 5.4s normally sound and run like they have a very very slight miss to them? Maybe it's the natural sound to these motors and I need to get used to it. I have a 2000 F-150 4.2 V6 and it runs and sounds like a perfect engine. There is no miss or hesitation right now but will drive a few days to see if anything changes. Thanks for the great suggestions and posts. I will update this post if the problem returns. I was unaware that there is a valve guide and/or rocker problem with these engines, thanks for the insight.

 

One more thing, I ordered the COPs from Uneeksupply and 2 out of 8 are bad or perhaps they did not seat correctly. The Nav is running good so I am not going to disturb them.

 

My 5.4 is the smoothest engine Ive ever owned and I have own quite a few cars and trucks. No thats not normal.

 

Defective cops are not unheard of at that price - they should replace them under warranty no problem. This is why we've been recommending the V-10 kit recently - that gives you 2 spares.

 

My EVR (evap regulator) I think it's called, sits on the right side of the of the throttle body (when u face motor), it's black and about the size of a pill bottle. Every time I turn off the 5.4 the EVR makes a moaning-gurggling sound. Is this normal or is this my culprit? I've read a lot of posts about the DPFE (the box that has 2 hoses going to the EGR exhaust tube) going bad. Could the DPFE be my problem? BTW, I do not get any codes.

 

Completely normal - The EVR is working as it should. hen they hum a tune after shut down, that's telling you it's working. - Just bleeding off, nothing to worry about.

DPFE is fine.

Told you what to do - don't ignore.