Explorer is making a tick then reving up 5k rpms?

[eddie!]

My explorer recently started making a tick noise then it revs up like 5k rpms then goes back to normal. It does it almost like every 5-15 seconds when im stopping, stopped, or just rolling out of a stop.. havent noticed it going fast yet. But it happened before and then my car started a constant rev @ like 30k rpms.. I replaced the thermostat and it was all good no problem now like 2 weeks after i replaced it its making this noise again. In all honestly I dont want to have to replace a thermostat every 2 weeks so im hope'n its not the thermostat again. anyone got any other suggestions of what it might be? its irratating as crap!

 

[my98nnj]

The thermostat has nothing to do with idle speed.

Clean the Idle Air Control Valve first and see if that takes care of it.

 

[eddie!]

The thermostat has nothing to do with idle speed.

Clean the Idle Air Control Valve first and see if that takes care of it.

Hey bro thanks but I figured it out well what makes the noise. I forgot I had my heat on yesterday and left it on and I just turned it off like 20 min ago went and drove it no noise at all. It only seems to do it when I have the heat on. I wonder why when I have heat on it does it though? I noticed something heres a pic I found to help you understand a little more.

Ok see that part in red connected to the belt? well when it makes the tick and revs the part like on the outside of the belt all seems to spin for like 3 seconds then stop and so on and so fourth with the heat on. Any suggestions?
Thanks,
Eddie.

 

[justinf89]

the tick you hear is the ac clutch kicking in and out. I can't tell you why its coming on when the heat is on though.

The part in red is the ac compressor, painted red?

 

[eddie!]

the tick you hear is the ac clutch kicking in and out. I can't tell you why its coming on when the heat is on though.

The part in red is the ac compressor, painted red?

Hey justinf89, Thanks for the quick responce. Good question the heat was in the middle just went out and checked so it was in the middle of heat and ac. But why do you think it would rev up like 5k rpms when it kicks in? And as for the picture I googled "1999 ford explorer engine picture" and found that picture. I think its like photo edited just to make the part stand out more possibly.

 

[my98nnj]

The A/C compressor will run in any setting except heat (floor) vent and off. Every other setting will cycle the compressor to take the humidity out of the incoming air.

The engine control will bost the idle speed slightly for the increased load caused by the compressor, although you really shouldn't see the idle speed increase, it should stay stable. As I said previously, clean our your Idle Air Control Valve and see if that helps stabalize your idle speed.