I have a 2003 Expy, 5.4 2WD, 178,000mi. It is idling rough, stalling at speed, hesitating. If it stalls going down the road I can shift to neutral, shut the key off and it fires right back up. It also lacks power and I'm only getting about 10-11 mpg, down from 15-17 mpg.
When it hesitates if I apply the throttle it is extremely unresponsive for a few seconds and then gains some power and gets back up to speed.
It used to just stall at stop lights once every few months, now it does this every time I drive it.
CEL came on and it is showing the following codes:
PO171
PO300
PO351, 352, 353, 354, 355, 356, 357, and 358.
I ordered 8 new COPs for it and picked up a set of Motorcraft OEM replacement plugs.
I also found a few vacuum leaks, replaced a couple of elbows that were cracked or collapsing, but that didn't seem to have any effect.
My parts won't be here for a few days, is there anything else I should be looking at in the mean time?
One mechanic told me the cats are clogged and another told me it just needs a complete tune up. The cats are not glowing red or badly discolored or anything. I did a search and tried the fix in the TSB with the wire rubbing on the A/C pipe to no avail. Could this be caused by the fuse block with the bad relay in the passenger side kick panel? Maybe a fuel pump or filter causing the lean condition on bank one?
Any help or additional information is greatly appreciated.

 

I was going to ask how many miles on the spark plugs, but since you're going to change them it's a moot point.

 

Yeah, I bought it with almost 170K on it so I have absolutely no idea how long they've been in there, so I figured it wouldn't hurt to change them while I was in there doing the COPs anyway.

 

any idea what kind of fuel pressure you have? being you have a lean code, and every cylinder is misfiring, i would say its a fuel issue. ever replaced the filter?

 

I haven't checked the fuel pressure yet. I was going to change the fuel filter when I do the plugs and coils though. I thought it was strange that every cylinder is misfiring, but only bank one is lean.
I reset the PCM a couple hours ago and drove it around a bit. As long as I'm easy on the throttle it runs OK, still rough, but the CEL doesn't come on and it doesn''t stall out until I get on the throttle a little harder like you would pulling out into traffic. Then the CEL lights up and it really starts running like garbage. Makes me think the fuel pump can't keep up with demand, but would that cause the random misfire on every cylinder and the lean condition in only one bank?

 

with every cylinder misfiring, and the lean code its more than likely fuel pressure. i would start with a fuel filter.

remember, you only got a code saying that bank was lean. that doesnt mean the other bank actually isnt when read in live mode.

 

nevermind, Im a *******

 

The misfire can be responsible for the lean codes. A misfire sends unburnt fuel into the exhaust where the O2 sensors detect a drop in O2 levels and in turn lean out the fuel mixture. So start by fixing the misfires and it can possibly solve all the problems you're having.

 

Other way around - O2 sensors detect unused oxygen when the mixture misfires and in turn richens the mixture to try and use the oxygen.

But, yeah, start with the misfires.....etc.

 

Just an update for anyone who is interested. The lean code was probably caused by a vacuum elbow that I missed when I changed the other two. It was on the passenger side bank and noticed it when changing out the 3rd coil back. New plugs, cops, and the misfires and stalling are fixed. No more codes at all after running it through three drive cycles.