2.3L ('02-'11) Mystery vacuum leak or something...

[Dirtman]

Just changed the intake manifold gaskets and slapped it back together, truck drives and idles smooth but idle was a tad high (950). So I unplugged the IAC and nothing happened. So first thought was a vacuum leak, did a smoke test and found a small leak at the vacuum port on the back of the manifold. I repaired it, reinstalled it and smoke tested again, this time no leak.

Now the truck will idle down to the proper rpm (850) but again, unplugging the IAC makes NO CHANGE in idle speed.

Fuel trims are also all over the place +15.6 at idle long term but bouncing around -2 to -7 short term. Hit the throttle and long term goes to zero. Another classic vacuum leak sign.

Also there's a line from the brake booster I cannot figure out the purpose of.
The red line comes from the air intake hose (non vacuum) but T's into the line from the manifold (under vacuum) that goes to the brake booster (blue line) WTF is the point of the red line. How can there be a non vacuum line connected to a vacuum line?

Right now I have all the lines just disconnected and plugged off to rule out leaks there but still seems like theres a leak someone. Smoke test not showing anything and either is the old propane test.

Wtf!?!?!?!?!

Any ideas here... im too frustrated to deal with it anymore.

 

[RonD]

A Ported vacuum hose hooked to a regular vacuum hose?
WTF indeed

That is an odd setup, AND on a brake booster hose to boot, putting a "T" on the brake booster hose was always a "no-no" in my book, also PCV valve hose.
Plenty of other vacuum hoses to tap

Whats the vacuum diagram on the rad support show?

 

[Dirtman]

No vacuum diagram under the hood. They don't seem to put that crap on newer vehicles.

Before I did the manifold gaskets I had never touched this line. Now if I hook it up the way it WAS the engine runs like crap. If I plug off the part that runs to the air intake hose and just go straight from the intake to manifold to booster it runs fine. (IAC thing is still bothering me but thats another issue).

Here is the fitting/check valve or whatever it is that splits intake vacuum and air intake tube.
The loop of hose on the black half is just what I used to plug it off because if you leave the black ports open its a massive vacuum leak. (You can see the hose is collapsed from vacuum pressure). The grey section goes straight through to the booster.

The second pic is the nipple where the line would normally connect to the black part of the strange fitting. (also plugged for now).

 

[Dirtman]

This is what it looks like when its hooked up the way it was before I took it apart...

 

[RonD]

Yes, then that's a check valve
Maybe the vacuum drop in intake was too low during acceleration or cruising at high altitudes so they added Ported Vacuum to keep brake booster "topped up"

Ported vacuum is only high when regular vacuum is lower

But that check valve may be leaking, or reversed, there should be no vacuum on the "black ports" with engine at idle, check valves should be closed
If Ported Vacuum exceeded regular vacuum then check valve would be pulled open and Ported Vacuum would add to Booster vacuum

 

[Dirtman]

I still cant figure out if I have another vacuum leak either. (Even with the brake booster nonsense plugged). My fuel trims are slowly resetting so hard to judge by them alone but like I said before if I unplug the IAC valve nothing changes. Idle RPMs stay perfectly normal at 850. Idle should drop like a rock with the IAC unplugged correct?

Rpms also kinda "stick" if you hit the throttle. Will stay high for 5-10 seconds then come back down.

Possible the IAC is just not closing all the way even when its uplugged?

 

[RonD]

Emissions laws do not like idling engines, under 1,000rpms pollutes big time vs over 1,000rpms
So RPMs often hang above 1,000rpms before dropping, but that IS the IAC Valve working

Also if engine idles higher cold and slowly drops to under 1,000rpms after full warm up that mean IAC Valve is working(and CHT sensor as well, lol)

 

[RonD]

Well, I can't find that inline 4 port unit listed any where, can't even find another picture of 2.3l Ranger engine bay of that area, lol.

 

[Dirtman]

Took the IAC off and checked it, operating good, not stuck, plunger nice and springy. So still a reason for the idle to hang when its unplugged instead of dropping way down.

The brakes seem to work perfectly fine without that line running to the air intake tube so Im leaving it plugged off for now and focusing on the idle/vac leak.

If it is a vac leak its gotta be small but its still bugging me...

 

[RonD]

That ported vacuum hook up would be for some specific reason and only on the 2.3l Duratec because haven't ever seen that type of thing on any other vehicle

 

[Dirtman]

That ported vacuum hook up would be for some specific reason and only on the 2.3l Duratec because haven't ever seen that type of thing on any other vehicle

Figured out the stupid check valve. I had the ported line from the air intake tube and the intake vacuum line reversed so the check valve was working backwards causing a leak.

And from what I can tell by fiddling with how the check valve opens and closes in 3 directions it must be to keep the vacuum pressure balanced between idle (high vacuum) and heavy load (no vacuum) by switching between the two ports. There is NO mention of this thing in my factory ford workshop manual... NOTHING. I did notice running direct to the manifold without the check valve in place the pedal would kinda drift from firm to soft based on engine load, with the valve connected properly its always consistent. Maybe the duratec has a weird vacuum pattern that requires this mess?

Still think the back of the intake is leaking. I put a new hose on from the intake to the vacuum resivoir and siliconed the crap out of it. When it dries ill check to see if its any better. The truck runs, idles, and drives smooth as silk though. Idles just hangs with the IAC unplugged which means air is getting in somewhere.

 

[RonD]

Good work and good news about the reversed hoses


Maybe the throttle plate is hanging open a bit, throttle cable binding, or loose plate or maybe the anti-diesel screw, if it has one

 

[Dirtman]

Good work and good news about the reversed hoses


Maybe the throttle plate is hanging open a bit, throttle cable binding, or loose plate or maybe the anti-diesel screw, if it has one

It doesn't have a normal anti diesel screw. It has a throttle stop (does the same thing) but it is absolutely non adjustable. The screw is set from the factory and they like cut the head off. Cant use any tool to adjust it, and then put tamper paint on it. I know that thing is wherever ford put it.

Im gonna try it again tomorrow when the rtv dries on the suspect nipple. Like i said, it must be a pinhole leak. But I'm a perfectionist so its driving me nuts.

 

[Dirtman]

My fuel trims were always a tad high (+10 or 12) but steady. Its going through a weird correction phase. Long term at idle will be 15 but short term -5.... so 10 total. The unplugging the IAC and no rpm drop is whats pissing me off. Before it would drop to like 550-600 and run rough. Now its just 850rpm with or without the IAC plugged in.

 

[BAN-ONE]

Maybe the iac needs alil tap,tap,tap aru