Well guys, been at a loss on this one! Any advice and help is greatly appreciated. I'll describe exactly whats happened. Fuel Pump failed three weeks ago so that was replaced at the shop for a whopping six hondo. Three days later I start having these issues.

Truck starts running bad, studdering on acceleration ussually around 1000-1800. While around 70-75mph if I let off or just try and keep it there steady it will studder as well and this is at various other speeds to. Bad fuel mileage somewhere around 120-180 at the highest.

Replaced all o2 sensors as they definetly needed that, the shop I had to my fuel pump did a "free" more like bs diagnostic test on it and told me the MAF sensor and 1 and 7 coils were bad. So those two were replaced along with the MAF and the pcv valvle as well. Im stumped here.. I'd really like to handle this myself rather than a shop.

 

Is only the one bank lean, or are they both lean? And does the problem get worse with colder temps?

 

Yes only bank one is lean, and yes colder temperatures do have a affect on it more so than warm.

 

A shake at 70 / 75 is usually an indication of a cylinder not firing, and you'll especially notice it at lower rpm's. But the bad idle in the cold, and bad gas mileage, and the leaning out code is more an indication of a bad Idle Air Control Valve (IAC). Plus the fact the dealership thinks it's the MAF makes me think they also know the engine is getting too much air. The IAC is a super easy change (2 8mil bolts and one connector on the back top side of the engine, 1/10 for difficulty) and you'll immediately notice a difference if it is the issue. It's more of a pricy part though, 60 bucks online, upwards of 240 at my stealership. I found one off a expedition for 20 bucks when I did mine.

As for the misfire, your best bet is to unplug the spark plugs one at a time and see if it makes a difference in idle. It might not show up until under load though, so you might be chasing that problem for a while. If you can acquire a friend that works at ford, steal his computer and VCM and go for a drive and turn on the setting that monitors plug hits, that'll instantly tell you if it's missing at all and on what plug.

 

Thanks man. Any way to test this IAC? Also, been reading up and It sounds like it could be the intake manifold. One thing I forgot to mention.. It has died on me several times while reversing in this cold weather.

 

Fire it up..let it idle...then unplug the IAC solonoid. If the truck dies its good...it it still idles but badly (no change) its bad.

Thats how I found mine was acting up.

Worth a try.

 

Extemly good information man. I wanted to point out you said unplug the spark plug, I think you mean COP.

 

I don't know of any way to test it really. Sorry. It might be the intake manifold gasket, but your IAC would be the first place I would start. And a bad IAC will make your vehicle die when coming to a stop, or putting it into a gear, any situation where your idle drops basically. Cold weather really compounds the problem which is why most people only notice it in the winter.

This test can work, but don't rely on it 100%, my truck would still run decently when it was plugged in, and then barely run when unplugged. Which would make you think it was good. So just use your best judgement

Haha, yeah, good call. I was working on my 4.2 last night and had it in my mind they were the same on the 5.4

 

i would also take a look at the EGR valve as the valve may be stuck. Also make sure the pipe from the manifold to the EGR is not plugged up. you can clean the valve by scratching off the carbon build up on the valve. i run a stiff wire through the pipe to make sure is it not plugged.

 

Cleaned out the IAC yesterday and put it back on and the little part moves inside well. Im taking the two ignition coils back to oreillys today to get My $140 back lol. And I'll see about the pricing on an intake manifold but I will test the IAC before I make a move.