Starting to look over vacuums for idle fluctuation & Ac defrost / panel vent issue

I have two issues that may be vacuum related. I have never gone after diagnosing vacuum issues before. I will outline the issues and questions are at the bottom:

First I do have an idle which fluctuates after a few minutes of driving from a cold start up. No issues on cold engine. The idle seems to get down to 550 and then go to 850. This occurs where or not the Ac is on or off. If in park or neutral, it seems to be normal and not fluctuate. When I do shut the Ac off though, it jumps to 1200 to 1400 and the fall back to 600 and then fluctuate if it had been prior. With this I do have the common air intake whine or humming noise.

Periodically at some stops, it idles normally at around 600-700.

So far I have quickly done the starter fluid spray test on a cold engine and found change in idle. I cleaned the air intake tubes, new motorcraft air filter, cleaned maf, throttle plate, cleaned iac but reused gasket. Looked over vacuum like the best I could. Found good build up on line from throttle body to vapor purge valve.... The build up was lots of dust maybe, but it was directly behind the egr. When I took line off, I noticed a tear at the Vpv connector... Trimmed it off and tube seems ok. After all this, I disconnected positive battery cable to reset ecm. It is still occurring but does seem the air intake whine is not as loud as before, but still present.



Next is the common, panel selection on the EATC blows out the defrost vents most of the time as defrost vents are the default. Sometimes the panels produce output, usually when slowing down and rpm drops below 1000 during a stop. Then on acceleration, it returns back to vent from defrost.

Looked over just a few lines that are easy to look at but nothing obvious.



So a few questions, from a newbie:
Are these two vacuum systems mutually dependent on each other?
Is there a good set of tests on the EATC vents to narrow down which vacuum lines and valves to look at?
Does it make sense to go after one before the other or start with panel vacuum?
Can someone point me to good diagrams for the entire vacuum system? Maybe detailing where some of these components look like or are located?



Thanks in advance !

I performed the starting fluid test another 2 times over many more areas of the vacuum system... nothing noticed.

I see videos and notes about the EATC and the interior solenoid o-rings can case issues with vent selection.... BUT is there a way to diagnose that prior to removal if the dash control unit? If it were that the o-rings were failing there, would that truly be a vacuum loss overall causing the main vacuum system to have that fluctuating idle?

You could rent a smoke machine to pinpoint vacuum leaks.

these engines are prone to intake manifold leaks . both on the coolant system and on vacuum system .
the plastic warps after time , can show up as several problems. Check with smoke or starting fluid. replacement only permenent solution , IF, that is the source of your problem

If it were to be the intake manifold gasket, I take either upper or lower, would the issue be always present? Sometimes mine acts ok at stops, sometimes not. I cleaned the iac again... Made sure the valve moved with slight pressure.

Seen one video where someone unplugged iac while at cold idle then again at hot idle to check positions of the valve.

I see the plunger open to vent both chambers at cold idle. Will pull off again tomorrow to see where it sits on the warm idle. I unplugged it when stopped at idle and no hum And a steady idle of 700 rpm.

I guess I want to find the ohm specs for the motor.... Anyone know them?
I will search now too.

Thanks

I don't see changes on the iac when removing under running or not.

There sure is a lot of carbon in the chambers below. I still have not found a vacuum leak.

I am wondering if it's just always a good idea when fighting this condition make make sure the entire throttle body and air intake is clean and then see where you are. Obviously it should be done to clean everything periodically right? I already cleaned iac, maf, air filter, throttle plate.

So I think I will do that, pull of throttle body, clean it and inspect ports to the egr... Seen some info saying these ports are probe to have great carbon build up. I wonder in doing this, should I pull the vacuum hoses off and clean them out? With the same spray?

Any advice or thoughts from the forum?

well, i decided to first clean up the EATC issue of not holding vent selection correctly.

I tested that between throttle body and the AC Check valve that there was 20 Hg.
I capped off the EATC vacuum supply line port at the firewall and tested that the reservoir (and it's line) behind the battery held while running and then off.

Vacuum test then on the EATC supply line showed it losing vacuum (but later I understand it that this should be the case, i.e. does not hold vacuum).

I took out the EATC module (radio did not have to come out) and found that it was the type where the solenoid braces are spot welded onto a frame inside the module.

I decided to do 2 at a time (i.e. one side at a time - seen in a You Tube video) but realized in the end that perhaps you should do all at same time.
I used a 3/16 bit to drill out the welds... chose that as I planned to rivet them back using a 3/16 pop rivet.
Some solenoid brackets were not perfectly straight originally... dont sure if that was an underlying cause in the long term failure of the orings though.
I bought an Nitrile Rubber oring fit from Harbour Freight and used the 007 size, 5/32 ID, 1/16 CS, 9/32 OD with a little silicone grease on them.
The mediocre you tube video I watch as a source and I followed, had me bend out the outside frame to removed each solenoid assembly... I should have drilled out all 8 welds first and removed the frame first rather than bending it out and back in again.
Back in and it worked on all settings for all vents.
Ran the self diagnostic and it came back all 8's - good.

I ran around stop and go and the idle fluctuation is still there... it was much better with the EATC line capped off, but the vents are working... well
I ran up about 1500 more elevation as I wanted cooler temps (83 to 90 F) to try to get my EVAP system monitor complete ....
drove 10 miles on cruise at 45 at a steady low incline and at around 1800 RPM... realized near mile 9 that the MAX AC was blowing out the defrost now....I stopped and parked at idle and the vents came back to normal again. I drove back down (mostly coasting) and the Vents were fine the entire way. Drove on Freeway at 65 on cruise and the vents remained fine. Any idea why the vacuum would have not been present on the drive up?

Later I read over a Taurus's troublehooting guide for the vents issues in the EATC. It does seem to imply that if the vents are all working then the EATC does not hold a vacuum. (steps i8 - i9)
I http://www.ford-taurus.org/taurusinfo/Reference/eatc_self_test.pdf


So is that the case? that the EATC itself is not holding a vacuum if tested from a good vacuum line at the firewall?

I did test each of the vent vacuum lines and all held vacuum (while EATC was out). Once I capped the outlet on main line for the EATC line, the idle was much better after about 50 miles, but I did have a fuel smell from engine area and maybe somewhere around the SUV... I was thinking perhaps that the EVAP system vented fumes or had operated at a high level. AFter about another 50 miles, the fuel smell does not occur any more.

If the EATC does not hold vacuum normally, then how much of an effect would it have contributing to an overall vacuum leak to the intake?

Do my assumptions all sound right? I just wonder as I am seeing more idle fluctuation when the EATC supply vacuum line is connected, even with it working properly. I do see the loss when applying vacuum to the EATC line is about even 1 Hg per second. Does the one inlet on the EATC without a hose (not used) actually have a use like allowing air into the EATC?

today I tested the vacuum for engine performance... put gauge on line run over to AC check valve (placed before it).

no real abnormalities showed up. it holds steady at 19 Hg at idle. Under load, WOT, deceleration, 2000 RPM, etc, it performs as normal, according to the webpage
http://www.fordf150.net/howto/diagnoseengine.php

Vent control issue

I have a comparative thing going ahead in my Ex and I've effectively expelled my awful air distribution entryway, it's no more! When I have the warmth set to windshield defroster just, despite everything I get some warmth and wind stream coming through my foot or floor vents, other than the defroster vents. I do not understand why that is, yet I can live with it. The warmth by my feet doesn't trouble me.

What I have seen as of late, is that I can hear my aerating and cooling compressor "clicking or cycling" on and off as I drive, particularly when stopped beside a bldg or divider you can hear it, despite the fact that I have the AC killed and everything is set to defrost and the hot temp side. I don't get any chilly air coming through the vents from the AC, simply that the compressor is cycling oddly enough. I don't know whether either is associated with each other some how. Is yours doing this also?

There are threads out there discussing that the Ac system is used when in defrost mode as to dehumidify the air to speed the defrost of the Windows. If the air flow is coming out of various wrong vents other then defrost, it seems you have a vent door issue. Search for vent diagram to see the various blend and vent doors.