1999 Ford Explorer "Moosing (V6)

Since we bought this car, it has had an issue where, after it warms up, it begins making a noise which I’ve seen described as “moosing” on the internet. In addition to the sound, the idle will decrease and will sometimes kill the engine.

I’ve seen this attributed to the IAC, and so I replaced it (twice). I have tested the IAC connections as well, and all is good. I have even run the car without the IAC plugged in, to try to reset the computer, to no avail. I feel like I have eliminated the IAC from being the problem (but maybe not.)

I have replaced the PCV valve.

I have replaced the water temp sensor and the thermostat (someone suggested this might affect the computer and rpms…)

I have cleaned the MAF and tested it per the Chilton’s manual. (tested fine)

I suspect that because of the idle and the engine seeming to be choking out when it dies, that there is a vacuum issue somewhere. I just don’t know where to start with this.

Any suggestions at this point will help.


Should we assume the check engine light is on?

If so, please post the fault codes

Can you hear any hissing with the hood open and the engine idling?

No, the CEL is not on. Other than what I listed above, the engine runs normally.

I can’t say that I’ve heard a hissing, but then again the humming is so loud that it might not be audible.

Could it be a clogged catalytic converter? Or a weak fuel pump?

You can determine an exhaust blockage with a vacuum gauge and fuel pressure at the pressure test port.