Thanks for the input Bluegrass. As far as the EGR is concerned, if I remove the vacuum line off of the EGR valve temporarily to prevent any EGR flow that should rule out the EGR system, correct? If this is the problem, I think I still have the old EGR DPFE and EGR regulator. The true problem I had was carbon in the TB, so the parts are probably good.

I had never used any fuel additives before this problem started, only to try to fix it. Since then I have a fresh tank of gas and new plugs.

 

Hello gtpenc & Bluegrass,

Bluegrass,

Can you explain in a little more detail "excessive EGR flow" and how to check for it w/out a code or will you always get a code?

Thanks, Sean

 

Just a quick update.
I put my old DP EGR sensor on thinking maybe the new one was causing too much EGR flow. I took it for a test drive and no difference, so I continued on up the road to the AutoZone to pick up an O2 sensor. I installed it on the passenger side (fun job). I took it for a test drive and it seemed to help, only minor stumbles, not completely gone though. It could be because it didn't have that much time to heat up.

My wife has a lot of driving to do tomorrow, so I'm sure she'll give me the full report. My wife is threatening to get a Honda or Toyota if I can't get this licked. I told her if it seems better then I'll put the other O2 sensor in.

Any feedback is appreciated.

 

To 5.4 150.
The operation gets a bit involved.
The EGR system is a closed loop configuration the PCM has complete control and monitoring of.
There are two versions used up to about 04.
The original one has a 3 lead DPFE sensor and a restriction in the pipe feeding the EGR valve.
The later version has a 4 lead DPFE sensor and the restriction is in the EGR at the point it bolts to the manifold.
Both systems measure for flow rate accross the restriction to tell the PCM what the state of operation is. The DPFE translates this to a signal the PCM acts upon as low, high or correct flow. This either sets a code or alters the program to cut back fuel and advance timing for the duration of that event as governed by throttle position and engine speed.
So you can see where a carbon blockage would cause a no-flow condition and it's code, even frozen water vapor in winter will cause a no flow until the engine warms up.
The DPFE has two hoses to monitor the flow accross the restriction. You can see then that if one hose or the other/both have a fault (split, folded, off etc.) the monitor will pick up all these conditions and report with the code that fits the fault condition.
Hope this helps in understanding the workings and that unless you back probe the sensor and know what voltages to expect, it is difficult to know that what you are seeing is right or wrong because it changes with changing runnning conditions.

Where the spark plugs come into the mix is that during the lean mix/advanced timing conditions, if the ignition system has marginal problems, the two can combine to cause a real headach to figure out which or both systems have a problem, then throw in water in the fuel to boot.
You can see how far this can go at times before all the problems are worked out.

 

OK, I've changed both O2 sensors and there is a +90% improvement, but there is still something not completely right. Here is my latest theory/question... I have a small oil leak that I can't quite locate. It seems to be coming from the head or valve cover gasket (passenger side). If it is the head gasket, could it cause a misfire? I dread doing that job, but if it will fix the problem and clean up the oil leak at the same time I might be willing to take it on.

 

See... O2 sensors go bad slow and most people think bad or good. As you say , you still have some issue, but I have found O2 sensors to impact drivability at > 80 K miles. Hope you don't have head gasket issue, that would take a while. Maybe fuel injector? Leak, dirt ? Good Luck let us know. Mark

 

I finally resolved the miss problem. I thought I had this thing licked about 10 times, but after a couple of days it would come back up. I wanted to post my updated findings in case someone else with similar problems doesn't go down the same long road as me. In the end, my problem was a bad coil pack. I will summarize below what I've tried to reach this conclusion.

1 - Changed all plugs and coil boots- did nothing but no big deal because this is a general maintenance item.

2 - Bought a coil pack and put on one cylinder at a time until problem gone- this would have worked, but I rushed after the 5th or 6th cylinder. Problem ended up being the 7th cylinder I would have checked.

3 - Changed upstream O2 sensors - odd thing was this helped but didn't get rid of the problem. This actually made finding the problem more difficult because the miss happened less frequently - odd.

4 - Cleaned and eventually replaced IAC valve - did nothing

5 - Cleaned MAF sensor wires with electrical cleaner - did nothing

6 - Tightened all TB bolts - did nothing

7 - Replaced hose from TB to EVAP solenoid - I thought I heard a vacuum leak, but this did nothing.

8 - Had transmission flushed - did nothing, this was an act of desperation but good general maintenance.

9 - Called a friend at the Ford dealership. He said, "Does it feel like a 'fish bite'?" I thought, that is the best description I have ever heard to describe this! He said 99 out of 100 it's a coil pack.

10 - Read another post saying to look for hairline cracks in the epoxy on top of the coil packs. Sure enough there was a very thin, scratch-like crack in one of them. Replaced it with the coil pack I had already bought. NO MORE PROBLEM!

I hope this helps someone else. This site is a great resource for solving these type of problems, but it can be frustrating trying to find exactly your problem. My quest to fix my problem got personal and the list above is abbreviated. I even asked the Ford technician when I took the vehicle in for the CC recall what he suggested. He said, "Man, you've done everything we would do. I don't know what to tell you." In hindsite, the problem was simple if you just know what to look for.