EGR Valve Smoke Test

[Saucer_Face]

Hi everybody,
New to forums, but I've been creeping them a long time. I just used a homemade smoke machine to check for vacuum leaks on my 2006 4.0L ranger. The only place leaking was at the EGR valve, at the holes circled in the picture below. I'm wondering if this is normal? These holes look like they were designed to vent after all. The smoke test was performed with the engine completely off and key out (if that makes any difference).

Every other test I've thrown at the EGR seems to indicate its working fine. It holds a steady vacuum, and when bench testing it, compressed air flows through the inlet to the outlet when vacuum applied. Is it still possible that it's bunk or leaking?

Thanks for any insight you guys can give.

 

[Uncle Gump]

Those holes are in the EGR to allow atmospheric pressure to the lower side of the EGR diaphragm. This allows the diaphragm to move up and down depending on vacuum applied to the EGR.

I think if you have smoke coming out of those holes the diaphragm is bad.

What makes you think you have a vacuum leak to begin with?

 

[RonD]

+1 ^^^

Put a vacuum hose on the EGR valve and suck on it, it should hold pressure.........forever, if not its bad

 

[Dirtman]

You want the man to suck on his EGR valve for the rest of eternity? There must be an easier test...

 

[Broosedamoose]

If you have smoke coming out of those holes then it means the diaphragm inside is cracked. If smoke passes thru then so does air which means it's no good.

 

[snoranger]

It’s not unusual for a small amount of smoke to come out of there. If it’s pouring out, it’s bad.

 

[Saucer_Face]

Thanks for all the replies. I've been having engine performance issues: hesitation on acceleration, misfires, surging. Codes show fuel bank 2 running lean, bank 1 running rich, with multiple misfires on cylinder 1, 2, 3. Fuel trim shows bank 2 running at +35% at idle. Interestingly, if I get the RPM up to 2500 fuel trim decreases, down to under 10%. A vacuum leak is on my list of suspects. I tried looking for any leaks with carb cleaner, no results, hence the reason for the smoke test.

I've also changed out spark plugs, fuel filter, air filter and PCV. With no effect : (

 

[RonD]

After engine is warmed up and idling, unplug the 2 wire connector on IAC Valve
Idle should drop to about 500rpms or engine may even stall, either means no vacuum leaks
If idle stays high then there is a leak

Was there any transmission or exhaust work done prior to this problem appearing?
I had a shop reverse my upstream O2s when they put the exhaust back in, so lean on one bank and rich on the other
O2s have generic plugs there is no difference in left, right or rear O2s plugins, except to the computer, lol

But there can be other causes for that
"Lean" in this case means O2 shows low voltage from too much Oxygen in the exhaust
On a single bank, mis-fires cause lean codes, exhaust manifold leak causes lean codes, loose O2 sensor causes lean codes, a plugged up injector cause lean codes, plugged up Cat converter(if it has a separate Cat for that bank) cause lean codes
Failing O2 sensor causes lean codes

Rich codes are way less common, especially on one bank of a two bank engine
O2 would be first suspect
Leaking injector the next
faulty computer the 3rd

High or low fuel pressure would effect both banks, as would MAF sensor issue

You can test for leaking injector by using "Clear flooded engine" routine, all fuel injection computers have this
Key on
Press gas pedal down to the floor and hold it down all the way
Try to start engine
It should just crank but not fire or start
If so no fuel is leaking in
If it fires or starts then fuel is leaking in

Clear flooded engine routine is initiated when computer is on(key on) and it sees 0 RPMs and WOT(wide open throttle), i.e. gas pedal to the floor
Computer will then turn off fuel injectors, but spark stays on, this allows driver to crank engine over to dry it out if it was "flooded"
Cranking speed is 200rpms
If engine fires enough to get to 400rpms computer will start injectors
If gas pedal is released the computer will start injectors

I use this every morning to start my high mile 4.0l OHV, gets oil pumped thru the engine before startup
And good to use after oil change to get oil filter and passages filled up again before "letting" the engine start by releasing gas pedal

 

[Saucer_Face]

Hi Ron, thanks for the advice, I didn't know a lot of this. Just got off work and ran through a few of your tests. When I unplug the IAC, RPMs drop to about 300. So a vacuum leak is probably out the window. The only recent work I've done on it is replace the brake master cylinder. Couple months ago I had the brake pedal fall to the floor, and found it to be leaking. I was so convinced that maybe it had destroyed the brake booster too, causing a vacuum leak, because these problems started shortly after. But this, and every other test I've thrown at it, and that the brakes are now working great--seems to say that's not the problem today. I also got a donor EGR from the scrap yard that holds steady vacuum. But no change with the swap out.

I went through the 'clear flooded engine' routine, truck doesn't start. The code reader I have is able to stream voltage readings from the O2 sensors. All 4 are fluctuating between 0.1-0.9v, if I spray some carb cleaner in a vacuum line, reading shoots up to 0.9v. They seem to be working to me.

I read that you can test for restricted exhaust issues by hooking up a vacuum gauge to an inlet vacuum port, and watching for vacuum falling off when the engine is pushed up to 2500RPM. I tried this too, and the truck passed, again. Holds a steady -20 inHg @ 2500RPM.

I just started getting into doing some fuel diagnostics. I plugged in a noid light to the fuel injector harness, and found the side that is running rich and experiencing misfires also intermittently goes through periods of absolutely no flash (maybe 30 second periods). Not sure if this is part of the problem, or just symptom of the problem? I heard that some systems will cut power to the fuel injectors when it senses bad misfiring to prevent raw fuel from entering the cat....

So it continues...any thoughts?

 

[RonD]

After engine is warmed up the Rear O2 sensor(S2's) should be stable at 0.7 or 0.8

O2s only see Oxygen, so "rich" means low oxygen(0.9v), "lean" is high oxygen(0.1v)

The O2s after the Cats should see low oxygen because the Cats burn up most of the oxygen to "cook" the emissions
So 0.7-0.8volt and stable because Cats are HOT
Volt will jump now and then as computer sends extra fuel(rich mix) to feed the Cats some fuel to keep them hot

The upstream O2s(S1s) should jump around alot but from 0.2 to 0.6v
Computer is constantly trying to balance the mix to 0.4v on the fly(after warm up)

If your rear O2 voltage is jumping around like the front O2s then the Cats are bad