Hi everyone and thanks for taking the time to read my post. Ok, so here is my problem... For the last month or so I've been experiencing an intermittent skip/misfire on my 2002 F150 4.6L. It comes and goes and it doesn't matter if it is in park or in gear. It also does it while driving (not just at idle). The A/C on or off doesn't make a difference either. It threw a CEL code and when I checked it, the only code was a P1000, which just states that it didn't complete the diagnostic cycle. So far I have replaced:
•Spark plugs
•All 8 ignition coils
•Injectors
•O2 sensors
•Fuel/air filters

I've also cleaned the throttle body and checked for vacuum leaks. Any thoughts would be greatly appreciated!!!
Thanks
Drawlins87

 

Drawlins, IF you used the correct replacement parts, there's just about only one thing it could be. Your EGR valve is partially stuck open. From your description, - this happens at all loads, supports this as well.

There's other less common issues, like perhaps your wire harness just above the AC accumulator is damaged. That has been issue with theses trucks in the past, just not as common.

What happens, the harness dips down above the accumulator and with time it comes in contact. This chaffs the wires eventually causing a magnetic disturbance, creating havoc with the ignition system.

 

Here's something I overlooked.

Your P1000 is coming from a KAM reset most likely, BUT if it is not, then your one or more of your catalytic converters bad.

I'm leaning more towards this as being the problem.

KAM = KeepAliveMemory. It's either reset via scanner or a cut in power/capacitor drain. So if you haven't disconnected the battery or reset it, your monitor (cat monitor) won't complete because they are damaged.

With the truck running the way it does, this will get worse as time goes on if not corrected.

 

Jbrew
Thanks for the tips. I'll look into it. The first time the P1000 code tripped I had not disconnected the battery, it came up the same time as the O2 censor and I had the Ford shop reset it for me(my scanner wouldn't reset it for some reason) It popped up again the next day, that time I did disconnect the battery and it came back on later that day. I haven't checked the EGR or cats yet, I'll get to that tomorrow.
Thanks,
drawlins

 

Try hitting the side of the EGR valve with a big screw driver handle or something while it's idling. Listen for change. Then suck test it at idle. That will move valve, should almost stall the motor if it's working at all.

 

If--if your getting P1000 code and no other code, it tells me power to the PCM is being lost.
Either the PCM power relay, it's contacts of a fuse seating issue sensitive to shocks of driving.
Loss of power like that will keep rebooting the computer into diagnostics. Momentary losses of power stops all functions even for fractions of a second. When there is no power no code can be set because it cannot determine any system causing it without power. Loss of power also clears any code set except the P1000.
Could be something else but that is my suspicion.
Good luck.

 

Jbrew,
I taped on the egr valve and no change (I'm not familiar with the "suck test"). I have a couple more things to test and if I can't find anything I'll throw in the towel and pay the dealership $110 to run thru it...

 

Bluegrass,
I went thru and checked all of the fuses/relays and as far as I can tell nothing is corroded/loose/ blown.

 

Yea, just look for EGR suck test and you'll find it.

 

Well... The egr and sensor works. I finally broke down and took it the the ford shop and had them look it over. The only thing they found was a slight leak in the lower intake gasket. (which I'm not entirely convinced is the problem) correct me if I'm wrong but wouldn't it misfire all the time if that were the problem?

 

My feeling it your not reporting your issue accurately.
A misfire (under the conditions you describe) would set a code.
An air leak shifts the fuel tables, set codes 171/174 and could cause poor idle and in extreme cases stalling.
Your not reporting any codes!
Something is not matching here.
.
The most telling was the code 1000.
With no other codes, something triggered the program into full diagnostics, what was it?
The system does not launch into a full diagnostics unless something provokes it such as the following;
Did you do a code clear?
Did you remove a battery cable?
Is the PCM relay intermittent or it's feed fuse? Could even be a lead connection in the power distribution box.
A loss of power will stop everything, even momentarily.
This is the only reliable info you have given which is what I based my reply on..
Where are we with this?
Good luck.

 

Bluegrass,
Thank you for the advise. I replaced the battery about 6months before the p1000 came up, and with that amount of time lapse I didn't think it would be the cause of the code. I had a parts store clear the O2 code, but that was after the p1000 was already there. I have replaced the feed fuse and I'll try replacing the relay tomorrow and see if that works. I have also checked all connections and everything seem tight. I just picked my truck up from the ford shop this afternoon and the only codes they saw were the 1000 and an O2 sensor(which I have replaced twice already). The intake manifold gasket was the only thing their tech could find wrong with it, and they wouldn't guarantee it would fix the misfire.

 

Ho-- wait! what code was cleared? You never mentioned it except as a CEL, only the 1000 code.
Anytime a code is cleared the PCM goes to full diagnostics and 1000 will set until all PIDS have passed, then it will clear.
The 1000 is not clearable by any means until all tests pass.
If you have no trouble codes at the present then there is no hardware faults detected.
The EVAP system takes the longest to run, may be many drive cycles.
If this is the case, I would do a power down to see if the program memory had retained shifted parameters due to a previous fault that is not there now.
Replacing any part for a fault in not an immediate fix until the program catches up with it over time, thus the reboot to get out of that situation and force it back to base program tables..
Good luck.

 

When the cel first came on it was just the p100 on the reader, and after driving for a few weeks I checked it again to see if it had a different code and it had the O2 code. I replaced it and had them remove the O2 code(like you said the p1000 can't be reset). Then it threw up the O2 code again(the same sensor I had replaced) about 2 weeks later. I've been driving for several months now and the p1000 code is still there, and I have driven over 800 miles. Does this help at all?

 

You got suckered on the new 02 sensor, it was just reporting a problem, that's like shooting the messenger for giving you bad news.

What exactly was the code number for the 02? That might help a bit.