2006 F150 Triton 5.4 stalls when stopped
 

Hi All,

Just joined the forum, here's my tale of woe:

Today I bought a 2006 F150 with the Triton 5.4 and 4wd from a private seller. I drove it around his neighborhood a bit and, aside from some exhaust manifold noise, it drove and rode very nice, so I bought the truck.

I got about halfway home (maybe 30-40 minutes of driving when it started dying at the stoplights. I'd have to re-start the engine, rev the gas a bit, and then put it into drive to get it going again. Limped it home and called the previous owner - he claims he has no knowledge of any past issues, which I'm sure is BS but there's not much I can do at this point.

I found a receipt in the glove box from the owner before him that shows the truck was brought in for misfire issues. The plugs, wires, and all eight coils were replaced at the time (this is about a year and 10,000 miles ago). The notes say that the previous plugs on the misfiring cylinders (3, 5, and 7) were burned so that the gap was .060 when it's supposed to be .044.

I also found another receipt from just a couple days before the previous one, where it was taken to a transmission place because of "lunging" when the engine is warm. Looks like no action was taken at that time.

So it seems like this has been going on for a while, and the last two owners have been just kicking the problem down the road to the next guy. Well, as the next guy, I'd like to resolve this. Anyone have any suggestions on what this sounds like? Timing chain? I'm pretty capable when it comes to working on older cars (pre-computers and fuel injection) but am not too experienced with newer technology. So far, it doesn't seem to be throwing a CEL, which is surprising considering how badly it was running when I got it home.

Weird side note - I took the air filter out to see if it was clogged, but it looked okay. I put it back in and started the engine, and it ran fine. I put it into gear and it didn't stall. This was maybe ten minutes after I first brought it home. That makes me suspect (and hope) that it's not the timing chain, but I'm not sure what it could actually be.

Any input is appreciated.

Thanks,
Nick

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Next time your engine stalls you can disconnect your battery ground cable, then quickly remove the MAF harness, and quickly connect your battery ground back. Please note when driving without MAF you can put your car in limp (fail-safe) mode and you get CEL but that's fine for diagnostic purpose, your AC and radio might not function, your trunk may lose power when it's in limp mode, just drive for 10 minutes or so around your neighborhood and your objective is see if the engine stalls again with MAF disconnected. When you are ready to plug the MAF back just stop the engine, pop the hood, and key out door closed, and wait 15 minutes, then plug the MAF back, you don't really need to disconnect the battery ground this time.
Are you sure your CEL is working? Do a bulb check real quick you can tell, turn your key to ON/RUN position, do you see the CEL and once you START the CEL should go away. Please also note that if the previous owner just did a CLEAR CODES the relearn can take 100 miles driving or a few days and during the relearn process don't disconnect your battery anymore. Also do not scare yourself on those receipts, you need to trust your good scan tool to find out more.

Thanks for the suggestions and info - if the truck still stalls with the MAF disconnected, is that an indication that the MAF is bad and should be replaced?

CEL is working, the bulb ignites on power on then disappears when the engine is started.

I have a feeling the PO cleared the codes, yes. Does that mean new codes won't start showing up until the relearn is complete? I feel like I've had new codes pop up right after they've been cleared on cars with chronic misfires in the past.

Thanks,
Nick

When you disconnect the MAF your truck will operate in fail-safe mode or limp mode with the factory predetermined air fuel ratio, and when everything seems fine except the lack of power, then your MAF is bad. When there is no improvement, then your MAF _should_ be okay. Don't worry about getting new CEL when MAF is unplugged, your goal is to narrow down the issues so you can move on to something else.
If your CEL bulb test is working and if your truck has major issues you should get the CEL anytime, or they are already in pending stage. There are Ford's specific DTCs that don't trigger the CEL. If you have a generic obd2 scanner you should be okay, but you still should ask your friend to borrow a good scan tool.