IAC operates normal holding a steady 700 rpm's yet app after 20-30 seconds a random hissing vacuum sound coming somewhere behind the middle of the intake manifold facing the firewall as if an electric valve is randomly cycling open for one second causing a vacuum leak and idle increase to 900 to 1,100 rpm's depending on how large the vacuum hiss cycle happens to open, once closed idle dropping down to the steady 700 rpm's while in neutral.
Other times going into a surge cycle between 500 to 1,000 rpm's every 8 seconds that will settle down to 700 then 900 to 500 rpm's while in drive with less of a rpm drop with AC on and cycling. At a stoplight with normal light brake pedal pressure the vehicle will want to surge and creep forward when the idle cycle rpm's peak, rather a PITA to deal with not being normal.
Cold start or sitting 10 minutes hot retarts the normal instant 1,200 rpm's (cold start peaks at 1,700) returning to 700 within 15 to 25 seconds later.
Disconnecting IAC valve, idle will drop down to app 350 to 400 rpm's a nice steady smooth idle detecting compression resistance pulses.
Sweet running 192K mile vehicle with one transmission issue, this a seperate new thread topic also requiring attention. A 9-03 production date 3.0 V6 Escape. Also in the stable a 10 V6 XLT Escape. The 04 feels and handles flat like a sports car vs the 10 Escape, 04 much firmer as if it has an optional sports suspension plus the hydraulic power steering vs the electric 10 Escape. THX.....~~=o&o>........

 

There are at least 2-3 vacuum valves in that area that are electrically controlled.

See if you can be a little more specific as to which area it may be coming from. Sometimes a piece of hose with one end close to your ear, not touching it, and the other end trying to hear where the sound is loudest. That should help isolate where the problem is originating. Be careful and stay away from any moving parts .

 

Thanks hanky for your reply. With just a quick listening and a look the vacuum sucking sound is below the line of sight from top of intake, i'd guess 6" to 10" below as well center of engine and below what looks like a vacuum accumulator vessel mounted horizontally on the firewall 3" x 10" long looking like a saussage. A large mirror then take a lookie what's back there out of sight would be smart and next, clamp off hoses going to each valve until that sucking sound goes silent then trace to what it's connected on. A vacuum lines flow chart would be great if there is one online being the next search step.
Presently in my area on and off showers 8 AM until 10 PM, not even able to do the normal checking around at Pick-n-Pull's in my area. The IAC unit, has been acting up even after cleaning and liquid graphite lock lube added plus a small plastic part the visor anchors to the loose end for a 10 Escape. Always on the hunt for 94 to 95 years only sold in the U.S. Land Rover Discovery parts. Two years only with a distributor, different intake runner design later 96 on up OB2 w/coil packs with computer controlled timing BS. OB1 for a reason, read and clear fault codes within 20 seconds plus this 95 is one of less than 2% sold in the U.S. with 5-speed which I have.....I'll report back my findings when I have a chance with dry weather, thanks.....~~=o&o>.........

 

hanky, sorry been out of state over a week with the Escape parked.
Checking the EGR vacuum line removed from the unit, idling then raising and revving rpm's idle to 3,000 rpms and releasing throttle quickly there was never a vacuum signal to the EGR in neutral, no load on the engine. Shouldn't the EGR get a vacuum signal by throttling up and down?

That hissing sound is more like a high pressure hydraulic psst sound of random times of half second and variable amount like a control valve partically cracked open from the seated position. Pulling off vacuum lines now check engine light is on.

 

The old EGR systems did respond to removing the vac hose. Newer vehicles have to meet certain conditions before the computer will allow vacuum to operate the EGR valve.. The systems are a little more complicated now.. Also, newer vehicles with variable valve timing no longer utilize an EGR system, not necessary..

 

hanky, didn't the 04 (9-03 production date) 3.0 engines have variable cam timing, two cams per head? While thinking at 3 AM there an rpm that must be surpassed before the EGR system begins to function like 3,000 or 3.500 and anything below that rpm the EGR is not being activated? Reason being I never went over 2,500 when testing for a vacuum signal with hose removed from the EGR valve.
Easter Sunday the only rain free day also not wanting to be a jerk with neighbors while the Easter Egg Hunt locals gathered for the day all in smiles BS thing, little kids 3 on up all over the street doing laps around the center islands, no parents watching for cars. Given time there will be a fatal as this is a public street and not a park only two blocks away. Yup they're also paying $22,000 plus a yearin property taxes. Same newbies on my azz for owning my 68 F250 called "THE POLLUTION BOMB" vs electric their vehicles BS. Yup raining again today (thursday). Cleared one fault code being PO511 IAC valve from removing the power plug, idle dropped down to 300-325 rpm's, it's functioning smoothly and normal. Pulled off a vacuum line to a plastic cannister mounted to the left fender liner again causing a "vacuum leak fault". B0??? numbers as a vacuum leak also cleared. One vacuum valve with two together hoses to molded rubber connector mounted on the right rear corner of the intake up high, one line going to the EGR valve possibly the suspect valve (?) of these random vacuum hiss (sucking sound) possibly not allowing EGR to function? This at idle when the EGR shouldn't be activated?

Will apply vacuum to the EGR valve checking function and movement along with diaphragm not being ruptured, 745 rpm idle with random to 950 to 1,100 spikes when the vacuum sucking sound appears from a short 1/2 to 2 seconds long hissing spikes, afterwards a quick dip to 550-600 then quickly back to normal 745 rpm's. Same results in neutral, drive or AC on or off with higher rpm's swings loading the engine down vs in neutral. No check engine light unless pulling off hoses having a high vacuum the normal vacuum leak reaction. Locking 12" medical forceps the perfect vacuum hose pinching tool......~~=o&o>......