Testing an EGR valve?

Hey guys,

Is there a good or convenient way to test that my EGR valve is working properly? 96 2.3

I'm trying to eliminate potential contributors to spark knock and I would like to test that the valve is working. I get great fuel economy (ranging from 24.5 to 29.8!!) so I feel like the valve is probably ok but it would be nice to test it anyway

Thanks in advance

Get a length of vacuum hose that fits EGR valves port

Warm up the engine and let it idle
Hook up your vacuum line to the EGR valve
Suck on it
Engine should start to stumble and should eventually die if you hold the vacuum long enough, but if it starts to stumble it means the EGR valve is opening, so no reason to stall the engine.

1996 EGR system uses a DPFE(differential pressure feedback) sensor to detect how much exhaust is traveling into the intake as EGR valve opens, it's a pretty accurate way to determine EGR flow because even if passages get carbon build up the amount of exhaust added stays the same because computer is basing EGR valve opening on Pressure changes in the EGR tube, not the EGR valves opening travel.
EGR is an Emissions system so computer will turn on CEL(check engine light) instantly if there is any problem detected, and set codes for the problem.

1994-1997 2.3l ran 9.4:1 compression ratio so could get "Pingy" on Regular gas(87 octane)
You could run some seafoam in the gas tank a few times, might clean up some carbon build up in the cylinders which increases compression and also holds in heat, which both cause pinging/knocking

Earlier versions ran 9.0 or 9.2:1 ratios
And the 2.5L(1998-2001) version ran 9.1:1 ratio
9.4:1 ratio is right at the edge of regular gasoline's pre-ignition heat range, so doesn't take much of a change to get pinging/knocking on regular gas.
You can run a higher octane and see if pinging /knocking is octane based, just to be sure

My man!

I'll try this out and let you know how it goes.

You have responded a ton in my spark knock thread for this truck- Thanks as always for that and this response.

The pinging is basically non existent with premium. I have run 6 or more cans of seafoam through the tank in the last few months, I have also done two crankcase seafoams and four seafoams through the intake. All of that has helped the spark knock, when I test on regular, but not as much as I had hoped, leading me to believe either there is as LOT of built up carbon, or that I have other problems.

Could the DPFE sensor negatively affect the operation of the EGR in case the DPFE sensor failed?

I have good double platinum plugs which are gapped correctly and pretty new, truck runs good and cold (full coolant flush recently), I have a feeling the egr is fine but I'm hoping sooner or later that I can run regular octane (solve the spark knock). I'm just being OCD as I am over details when I should just run premium.

Yes, DPFE sensor could cause issues, but computer monitors it pretty well

DPFE works by having two hoses to EGR tube:
Make sure these are clean, they tend to get water build up because Exhaust has water vapor in it, and these hoses cool off faster than rest of the exhaust system so get condensation inside, DPFE sensors often fail because of moisture inside.

These two hose have the same Pressure when engine is running and EGR valve is closed, so DPFE shows no difference in pressure
When engine load is increased computer will start to open EGR valve and the hose closest to the EGR valve will show a higher drop in pressure than the hose that is farther away, and that's the pressure deferential the computer uses to gauge the flow of exhaust gases into the intake.

I suppose it is possible for DPFE sensor to fail in a way that won't set a code, i.e. showing higher differential pressure than it should when EGR valve is opening, so not enough exhaust gases are flowing in.


Just to take it off the table, try running with one coil pack unplugged, CEL will come on.
Engine does have better performance with dual spark plugs, but if computers spark timing between the coil packs is slightly off...........

Pre-detonation, pinging/knocking, is when air/fuel ignites at different places in a cylinder at different times, the "ping" noise is the separate explosive wave fronts meeting.
Diesel engine noise, but diesel engines are built for this

Dual spark plugs are better, but spark timing needs to be precise, or you would get pinging

There also may be a computer software update for your year that advances spark timing a bit more to prevent pre-detonation

Thanks for explaining the whole DPFE thing, I never understood how that worked.

I am a little confused about one thing from your above explanations that I was hoping you could explain. That is: you said the egr opens under load, but isn;t there less vacuum under load? If its opened with a vacuum line, and vacuum decreases under load, how does the egr valve manage to open? Sorry if those are stupid questions

Great idea on the coil packs. Does that mean one coil pack covers exhaust side plugs and one coil covers intake side plugs?

Interesting note about a software update, any idea how I could find out if that's the case? not that I imagine I can do anything about that now

Call or stop by Ford dealer and they can look up your VIN and see if there is an update, you do have to pay them to DO the update, but not to look if there is one.

EGR Solenoid is connected to the Vacuum reservoir, so has stable Vacuum source regardless of intake vacuum.
Computer opens EGR solenoid to send a little or alot of vacuum to EGR valve, it pulses the GROUND side of the solenoid to do this.

There are codes for EGR Valve not opening enough or opening too far, set by DPFE sensors pressure differences
So if there was a vacuum issue at EGR you should get a code for that

Vents in the Cab also use same Vacuum reservoir, Defrost is the default vent, Panel and Floor require vacuum.
Say you have Panel selected while driving and you accelerate, if air flow slows down and starts to blow out Defrost vent, that would be a sign the Vacuum Reservoir may have a leak, and that would effect EGR system as well.
Odd how things that would seem to have no connection.......are connected

I would have said that unexpected deflection of the airflow from panel to defrost indicated a problem with the check valve, not the reservoir.
The reservoir will slow the deflection when manifold vacuum drops, but will slowly allow it to occur if the check valve does not contain the vacuum and allows manifold gas to bleed into the reservoir.(higher vacuum in the reservoir until it equalizes with the manifold vacuum)
You can add a check valve on the vacuum line leading to the reservoir without locating/replacing the original failed check valve. The reservoir should have a check valve in its connection to the manifold, and a TEE that allows vacuum to operate the EGR if equipped (some have a hold solenoid valve), and HVAC control panels.
tom

I have a 1996 2.3 Ranger as well that I just bought in June, I was going to tell you that there is no vacuum line and its computer controlled as the last two OBD-II controlled cars that I had the EGR's were computer controlled, but I went out and looked and much to my surprise the EGR actually does have a vacuum line on it.

So anyway... if you want to test it get a vacuum gun if you don't have one already (Harbor Freight has a cheap one), and disconnect the vacuum line from the EGR valve and then plug it off, hook up the vacuum gun to the EGR valve and then start the engine.

Once the engine has warmed up and dropped back to idle pump up the vacuum gun... somewhere before you get down to negative 30 psi on the vacuum pump gauge the engine should stall due to the massive vacuum leak that you just created.

If the vacuum pump will not drop pressure and the gauge just stays put or it just keeps popping back to where it was the diaphragm in the EGR valve is bad and has a hole in it and will need to be replaced.