Navigator 2004, 5.4 4V DOHC InTech , IAC valve small atmospheric vent on top. Smoke comes out of this vent during a smoke test. Why? Is this one way pressure out , but vacuum ok ? [ So smoke test is very low 1 2 psi from a hand held Harbor Freight transfre pump and a dutch master cigar smoke source ] I have not been able to test this device by using vacuum only on the ports , with the device on the bench, to see if this atmospheric vent is one way- relieves pressure, but closes upon vacuum. I think it would be closed when. vacuum is in the system. ? I have seen on posts that even a new IAC valve does this behavior… And one guy sealed up the vent with jb weld and then tried it on his engine and the engine ran barely and even more poorly than before … I am thinking about starting engine and then go with propane near that vent when it is idling and see if makes any difference with engine.. I bet it does not ? Anyone have experience in this issue ?
So for a continuation of the smoke test , it looks like that I will have to block off the IAC as well as the throttle body , to test the rest of it… I do get very good vacuum readings for the engine in general with a vacuum gauge method used by old timers to test the general engine vacuum and holds steady around 22 23 lbs over on the other side near where they are using vac for a reservoir and the IWE solenoid and a vac line going into the AC dash hvac controls… So, Might not even bother with it at this point.
Thanks, Will and the Skull Shakers in PA
Well to begin with, if you really have 12 psi smoke pressure that is way too much you're never supposed to go. Maybe over 2 psi. So I would start there. You can't over pressurize vacuum systems. They do not handle much pressure
@scottykilmer Well it is maybe 1 psi, whatever the hand held transfer pump that you activate with your hand can supply,, I had forgot to place a comma in there. “. , “. 1. , 2. psi. not 12…. In some ways the smoke test with even 1 PSI will not show you all things, example, if there is some breather or vent on a device, like I do see these breathers, vents on EGR solenoids, PURGE valves, and IAC valves, they all have these on them for whatever reason, then on the other hand, I have seen IAC valves on some other cars without any breather or vent ! So what gives here ? And when doing smoke test, it is a slight pressure like 1. psi and not a vacuum, so we have to consider the behavior of any ONE - WAY. vacuum valves in the system ! I think if IAC is working fine then I will leave it alone. You can see the passage way for the air it works with get grimy like the throttle body does. Cleaned TBody recently best I could on this 5.4 dohc, with it still on the intake manifold, and it made a WORLD of difference in having a normal steady idles…. I can say the Ford/Lincoln 5.4 Intech DOHC is a wonderful engine so far, but it is very sensitive at idle to any filthy TBody or other problems. MAF, EGR, PURGE, DPFE, EGR solenoid are all good and tested. Engine uses NO oil at 253,xxx miles