Alright, as most of you know I've been having a slew of minor issues with my 5.4L, and now I've got more evidence to indicate a real problem, but hopefully someone on here will recognize this and point me somewhere other than the dealer... who's verdict was "replace everything until it stops"

My passenger bank of cylinders are running VERY lean, and my driver side bank is running fairly rich.

I pulled my O2 sensors and changed them, my passenger 02 sensor was arctic white, like my plugs.... and the driver side was full of carbon. After the new O2 sensors were installed, the engine still ran like crap. If I unhook both O2's the engine runs like a champ.

I have searched for a vacuum leak, finding nothing. Lots of ether and propane were involved. Physical inspection yielded no results. Still no codes, lots of 'misfires' and I'm averaging 16MPG by hand and 16.4 MPG per the trucks overhead... and I know this truck does not do this when healthy.

Also, I repulled all spark plugs, and every single one is arctic white. Does anyone have any idea what would cause this? Are there any known manifold problems?

My buddy who's a powertrain engineer at general motors (I know I know) suspects a cracked exhaust manifold or intake manifold, and these 'misfires' are actually lean pops... then the computer pulls timing to reduce the knock and throws it all out of whack. Seems a little far fetched but I dont have anything else to go on, please advise if you can. The dealership has been of no use other than draining my account tell me what I already know... its broken.

 

Well first off, if the motor is split running one bank lean but the other bank rich, you can rule out a vacuum leak. But you also mentioned that all plugs were running white which indicates a lean condition, so I am prone to think more along the lines of the monitoring system, i.e. MAF sensor or ECU tune. Run a check on the MAF and make sure that it is within spec. Pulling the O2s will cause a rich condition, which will counter the lean condition, so that is right along the lines of a MAF issue. You might also be running lean because of lack of fuel. Have you put a gauge on the rail and checked the fuel pressure just before the injectors? You can pretty much rule out injectior failure as they don't often go out all 8 at a time, but you might have a blockage in the fuel lines, fuel pump going out, clogged fuel filter, etc. How long has it been since you changed the filter?
The lean pop could be caused by a cracked manifold (intake), but that would be cylinder specific, not all across the board. I could see one entire side being leaned out if the manifold or manifold gasket was leaking, but that would cause an issue on that bank only, not across the entire engine.
Run a MAF test, then check back with us. Hopefully you will find the issue there, but if not then post up and we can move on to other options. Good luck!

 

Fuel filter was changed a couple weeks ago, along with the plugs for the second time in a month or so period.

I've cleaned the MAF, what is the proper procedure for knowing what i's doing without tuning software?

 

According to my netsurfing I guess there is a DPFE sensor, on the EGR circuit that can fail and cause lean condition. Has anyone ever heard fo this little bugger?

 

Not familiar with the one on your truck in particular, but in general the DPFE is a sensor that measures the pressure on both sides of the EGR valve so the computer can determine if the valve is open or not. (When the EGR is open, there will be no difference in pressure.)

 

the DPFE has the two small tubes going to it, next to the bigger EGR tube, coming from the exhaust manifold. Usually they throw a CEL code, saying poor EGR flow or something...also I recall surging near idle by a few hundred rpm when its bad.

Tennessee's logic makes sense. How many miles, and any recent work before the problem started?

 

Ive got 160K on the motor, and this started about 5K ago just out of the blue. I was getting ready to go thru a car wash, and the motor just stalled, once I fired her back up it has run this way ever since.

First I thought I had a bad coil pack- turns out they are all good.
Then I thought clogged injector/ plugs- 10 cans of seafoam later and 16 new plugs problem still persists
Then I figured it was my o2 sensors as they were original... 2 new o2 sensors and the only change is now it runs like crap and I get awesome economy.

I changed my fuel filter about 3 weeks ago as well.

This is driving me nuts because I can't figure it out~ and I'm certain this is going to be a fairly simply fix, I'm just not looking in the right place.

 

Im not familiar with the mod truck motors, are they like mustangs in the way that they are returnless systems???

Could be trash stuck in that side of the fuel rail, see it on GM vehicles on a regular basis, especially on returnless fuel systems.

 

I'm not certain because I don't have any experience with mustangs, but what I do know is that the mod motor family is supposed to be universal~ only real changes across the board are # of holes in block, stroke, cams and tune.

How do I know if there's crap in the rail? A pressure test would pass if it's not completely clogged, but even if the pressure is there doesnt mean enough fuel is.

 

Would you have access to a real time data analyzer, like one of the higher end Equus OBD2 monitors?

I've found looking at what all the sensors are telling the ECU can be very helpful when diagnosing things like this. What ARE the 02 sensors telling the engine?

On thought: Any chance the O2 sensor wiring is swapped? Like the left side sensor is plugged into the right side connector? That would explain what you're seeing....

 

I'm not the original owner so anyhting is possible... but everything looked stock. And I don't have access to a real time scanner, HP tuners claims my truck is supported but they lie. The dealership didnt see anyhting but... I would love to know of a real time scanner to see what's going on.

 

I mean does your fuel system have a feed line and return line or just a feed? Im pretty sure it just has a feed line only (returnless) Look on the rail and see if you have one fuel line or 2 connected to the rail. Only way to clean the rail is to pull it off, remove injectors and clean it really good with brake clean or carb clean and compressed air. Be sure to remove the pressure transducer before cleaning if you decide to do it.

 

Well guys, the problem has been resolved. It is relative to coil packs, but not in the manner one would typically expect... hence why my new coil set and musical coils didn't reveal the problem:

Anti-seize

I've always been taught to put a bit of anti-seize on the plug threads so they won't corrode into the head. Anti-seize is also not a conductor, and well as we all no Spark Plugs are electrical devices that need to ground. Apparently the Ford Modular Motors are real finicky about anti seize, and even if you use it and they run fine (the last 50K of my old plugs) they are really straining the coils to deliver the power they need to spark.

I did have a coil pack on the way out, and it was replaced along with the spark plug it sits on. The anti seize was removed and now she purrs like a kitten.

What was happening was at low RPM, there was not a steady ground and #2 was misfiring. Detecting the misfire, the computer pulled timing, causing more misfires hence why it was always random and I couldn't find it. Not to mention all plugs were coated with anti-seize and not performing to their full potential. Thus, my engine ran like dog $&*!

All is well, and as suspected the unfindable problem was really simple in nature. Thanks for all your help and remember: anti-seize has its place in the automotive world (trust me--in MI that stuff is almost gospel) but its place is definitely NOT on spark plugs

 

Also just a follow up, the mechanic did say that most of the coil issues he sees on Modular Motors is a result of anti-seize... the vehicles with coil issues and no-anti seize are few and far between. So if you got anti-seize in your plugs, GET IT OUT!

 

Glad you got it fixed. Actually, I do use a little antisieze, but just a very slight dab. Lots of people overdo it thinking it is needed. Good job fixing it!