+1 with ur milage i wouldnt doubt some of the COP's are going out take it to a delaer to find out. they will hook WDS up to it find out if one is needing more power or supplying less then normal. id go with NGK iridiums their about 48 bucks on ebay for a full set.

 

After about 6 months of running crappy, rough idle sometimes, not as much power sometimes, other times ran great, finally threw a code, misfire on #1. Mechanic put in new plug and cop, took a drive and came back misfiring even worse. Pulled the PCM and cracked it open (voids warranty) and found the #1 plug pin on the circuit board was shorting out, melted, lots of carbon all over that area of the board, had been doing it for a long time. Put in new PCM with latest update ($500!@#$%!) and the little pony puller is running the best ever. Just my experience for what it's worth. Good Luck.

 

Red,

Any lead past the MAF will contribute to the problem. It will allow in unmetered air. If the leak at idle is big enough it will stall the truck. Because the problem started with a plug change I would change the boots. It shouldn't cost more than $4.00 each. Try Autozone, NAPA and such for the boots. They come with the spring connector in the boot.

JMC

 

JMC, I had a leak a long time ago, and it ran horribly, but since then I have checked and re-checked for leaks with none found. But something curious, I unplugged one of my vacuum hoses (the opne to my boost gauge) and it made very little if any difference, but I could definately feel the vacuum. ( it normally idles around 15-20psi vacuum)

I just replaced the plugs again, this time with oem Motorcraft plugs. Well guess what...
it runs like SH*T, maybe not quite as bad, but not much better.

So, it's definately not the plugs or the boots, all the boots checked out fine, no cracks, tears or othewise, they actually all look almost new.

Fasterhorses, maybe I have the same problem as you had, not sure, but I don't want to have to buy a new ECU to find out...

Here are two videos of my truck I took last night, one idling in park, and then I tried to hold it at 1500 RPMs, and the other video is my truck idling in gear.

Truck in neutral
Truck idling in gear (reverse)

I hope these are any kind of help. It seems at times to run perfect and smooth, then it goes nuts and loses it. WTF is this, I am really beginning to wonder if my ecu is dying.... I don't have any other explanation, it's not consistent at all, it'll run fine for 5minutes, then crap it's pants for a minute then run well for 3min, etc... If it were fuel or spark it would be a consistent misfire or stumbe correct?

This stuff always reminds me why I love my carburated camaro with no stupid computers.

BTW, the vids are really dark, sorry, but it's the sound that is important, if you view the vids with windows media and increase the brightness you can see the tach.

 

The ECU or PCM (computer) can be opened for inspection and then closed and still be used just fine but the warranty sticker will be broken that's all. The shorted piece was part of the connector where you plug in JET chips or SuperChips etc. I have no proof but I had plugged and unplugged my JET chip several times over the 2-3 years I used it trying to determine if it worked (it made no real difference) and I think I tweaked the board cause there was lots of black soot inside the PCM from years of arcing and never a code until complete failure and the code did not mention the PCM just missfire on #1. I think it would also be possible to get something stuck between those tabs on that connector (causing a short if you have used it) because it has lots of dielectric grease on it from the factory that will collect and hold junk. Good Luck.

 

What did you disconect to do the plug change? Fuel rail? Coils? Please list all things that were disconnected and or moved out of the way.

JMC

 

Okay, On the passenger side;
Aftercooler was removed,
the fuse box was moved,
the PCV valve was disconnected and moved,
the COP's were moved,
Injector wiring was disconnected to acces COP holding screws,
the wiring harness along the valve cover was left alone,
and the heater hoses were moved upwards without removal.

On the driver side;
All pluming to and from the supercharger was removed, including the MAF and all related wiring was disconnected,
the FMU was moved without disconnection,
assorted vacuum hoses were disconnected,
Fuel rail was disconnected and moved without removal,
and COP's were moved.

I think that's eveyrthing, I reconnected everything, but perhaps I missed a vacuum hose somewhere. Are there any vacuum hoses located where they are difficult to see?

thanks for any help

 

That part about trying to hold the engine steady at high idle rings a bell. Mine did the same thing. No code thrown. I couldn't figure it out either. Then it threw the P0401 code. I changed the DPFE, and the idle issue has gone away. Just a thought.

 

When you say DPFE, I assume you are referring to the EGR valve? (Differential Pressure Feedback EGR) Mine was replaced about 5-6,000 miles ago when the shop that installed my headers broke the old one...

Or are referring to something else?

 

have you checked voltage at the throttle position sensor? it might be your problem, or it might not just something else to rule out, if it was going out it could be causing a eratic idle, if memory serves it should be at .988 at closed and about 4.88 or so full open, good luck traking down the problem

 

I would take a close look at the PCV valve and the hose leading into the throttle body elbow. Are all the fittings to the supercharger tight? The irratic idle sounds like a vacuum leak. The trouble holding the higher rpm sounds like a loose connection in the intake tract that leads up to the throttle body. Are the boost levels still normal? Or are they a tad lower than normal? Onle last thing to check would be the inlet piping goint to the IAC. Is is clogged with anything?

JMC

 

DPFE is the sensor that determines that the EGR is actually working correctly. On my 5.4, it is located on a bracket bolted to the throttle body, near the inlet. It has two vacuum hoses on it. One is larger than the other. The old one was metal cased, and the new is plastic. About $60.

When mine went, it threw a code, P0401 I believe. But it did act the same on the high idle symptom. If I tried to hold it at say 2000, it would jump up and down several hundred RPM, and I could not hold it steady. I think this is because the EGR valve was opening and closeing when it wasn't really supposed to be.

 

I know exactly what part your talking about. When the shop installed my headers they had the two vacuum hoses switched and the CEL illuminated. If it's only $60 maybe I'll try replacing it. Is there any way to determine whether or not it is function correctly?

 

I think there is a test for it. Do a search here for DPFE. I think I recall seeing a test procedure. I didn't do it, just replaced because of the code, and the great help here.

Here is the link from Brian 5.4.

https://www.f150online.com/forums/sh...ight=DPFE+Test

 

Thanks esoxshep, I'll have to check that when I get home tonight... keeping my fingers crossed...