08 LTD Recirculate button shuts off by itself (resolved)

[pjw73nh]

Ok Here's the deal.

I have the automatic dual heater/AC controls in my 08 4.6L Ltd. The issue is that the recirculate button shuts off by itself. I have a pretty good understanding of the heating and AC controls in many vehicles.

Why is this important? I have some sort of fuel/fume leak that no one can find. Dealer admits it smells, but can't find it, and I'm not going to to start throwing parts at it until we KNOW what it is.

Back to the story. These fumes even though they are slight, come in to the passenger compartment when recirculate is off. Usually when stopped at a red light or parked with the engine running. If I turn on recirculate they go away.

The recirculate function shuts off at random intervals.

I use the heater in complete manual (single)mode. No auto, no AC. Manual fan. I fully understand that when changing certain modes of the heater that the recirculate position can change.

I also understand (and don't like) that regardless of state (on or off) the recirculate button defaults to off when restarting the vehicle. I wish it would stay in whatever position I left it in.

For example On a 15 mile trip, I can set the heater controls to manual, floor only, fan on 2 bars, temp on 85 (single mode), and recirculate on. Without ever touching the heater controls again, at some time during that trip I will smell the fumes, look over at the heater controls and recirculate is off. I can turn it back on and it will stay on for a random amount of time. I've never timed it.

Owners manual simply says:

2. Recirculation control: Cools the
vehicle more quickly by recirculating
the cabin air instead of using outside
air and helps prevent unpleasant
outside odors or fumes from entering the vehicle. Press to turn on/off.

Thoughts?

Thanks.

p.../NH

 

[Ornery]

Have you run the "Self Test" yet?

You're probably wondering the same thing as me. Whether the manufacturer would even allow a vehicle to run on recirculate indefinitely? I honestly don't know, and can't find that answer anywhere, but wouldn't be surprised if that turned out to be the case.

There's got to be a way to find that fuel leak. There's no way I could live with it. It would give me a headache!

 

[brianh]

Not sure about the recirculate issue, but the gas fume issue sounds like you may have some loose spark plugs. I had that same problem on my F150 with the same conditions you described. Well it turns out the shop left the back four plugs so loose I could unscrew them by hand. This happened to me on the 5.4 Triton engine which had the same issues I hear that the 4.6 has with spark plugs.

 

[pjw73nh]

UPDATE:

Thanks for the replies. Given that this is a 3 valve engine, I doubt the plugs are loose... (Fused in with carbon would be my guess). I am hoping at some Point the fume issue will "declare itself" and I will see or hear something tell-tale.

Well. This explains the recirc issue: I looked in the shop manual. Four minute time out until it returs to "fresh air".


https://picasaweb.google.com/lh/photo/nY9CvaToB5goZObWD-rXeBIQuLocPI1hSTTNR2owYGg?feat=directlink

 

[brianh]

Glad to hear you figured out your problem. From your signature it looks like you purchased your vehicle used. If you did not change the spark plugs you never know if someone else did and they worked loose. I would definitely give them all a crank to eliminate that option. You wouldn't want to be traveling somewhere and have a spark plug blow out and strip the threads in the head, which can very well happen. My F150 engine was a 3 valve as well, and surprisingly not very corroded at 60k miles and none broke while coming out.