I am guessing this belongs in this section.

Getting codes 172, 326, 538.

172
(R,M)
Oxygen sensor not switching - system is or was lean - Single, Right or Rear HO2S - Fuel control

326
(R,M)
Pressure Feedback EGR shows low pressure EGR not seating or not seating intermittently - PFE

538
(R)
System did not receive "goose" test - TESTS

The truck will idle fit then every no and again it will bog down and the battery gauge will drop then. It happens for a few seconds then the truck will go back to normal. It will happen every so often. Also recently while driving some mornings to work the when I left of the gas, the truck will continue to climb rpms. I have checked the throttle linkage but everything seems to be working fine there. It will climb and then after a couple of seconds it will fall and go back to normal. I've cleaned out the MAF and the IAC and nothing has changed.

Any help on what to do?

 

538 is just a test that you didn't do so not a concern.

EGR code 326 would be the first one to tackle since it could cause the O2 sensor code.

It reads that the EGR valve isn't closing, "EGR shows low pressure EGR not seating"

DPFE = Differential Pressure Feedback sensor
This sensor reads the pressure in the exhaust manifold and the EGR exhaust tube, when EGR valve is closed the pressure should be equal, when EGR valve opens it's exhaust tube will show slightly lower pressure than in the exhaust manifold, computer monitors this change, if there is a pressure difference when computer has EGR valve closed then it would set this code.

DPFE sensors are a common failure point on Rangers, but in your case you have a symptom in the engine stumbling, so ERG Valve is probably the problem.

EGR valve opens to allow exhaust gases in to the intake to cool the cylinders when engine is under load, yes you read correctly, the HOT exhaust gases cool the even hotter cylinders, lol.
But the EGR valve should ONLY open when engine is under load, accelerating or going up a hill or pulling a load or............ect, under load.

If it opens any other time RPMs can go up, its like a vacuum leak, or engine can stumble from exhaust gases fouling up the computers air/fuel mix.

So first step would be to remove the EGR valve and inspect it for carbon build up, this carbon can hold the valve open when it should be closed.

If valve is clean and seems to operate as it should, then follow it's vacuum line back to the EGR modulator, this is a 12volt solenoid that the computer controls, computer uses this to send vacuum to the EGR valve to open it, and cut off vacuum to close it.
Replace this part if EGR valve was clean, it is not cutting off the vacuum as it should, which holds the EGR valve open.

In any case when you clean or change anything on an engine you need to reboot the computer to store current codes in memory and see if the changes you made prevent them from coming back.
You can do this reboot with a code reader or simply unhook the battery for 5 or more minutes, which you should do when working on a vehicle in any case, these "newfangled" electronics do NOT like shorts, the "oops" factor is very high.


After EGR system is back to normal wait and see if O2 sensor code comes back.
O2 sensor reads oxygen level in the exhaust, reburning exhaust gases(EGR open) changes those levels and if computer is not expecting that change it thinks O2 sensor is acting up.

 

So I don't think the EGR has carbon build up. I tried to take it off but the pipe that goes to the EGR will not budge. When I went to clean the throttle body there was nothing to really clean, it looked brand new still. truck just hit 100k. I'm thinking about just changing out the modulator? Is that the one on the engine or the one on the fire wall?

 

Follow the EGR valves vacuum hose, it goes to the modulator.

This thread has pictures '95 of Modulator and DPFE locations on 2.3l: Ranger 2.3L P0401 fix plus bonus PCV replacement - Ford Explorer and Ranger Forums "Serious Explorations"®

This shows both being on the passenger side of the engine, not sure if that is different for '94

 

So just now got around to taking off the EGR. was all clean. tested the IAC voltage and it was reading around 10. everything was clean. ranger hasn't been driven much, just hit 100k. I'm thinking it is a vac leak or something with the a/c.

When the a/c is not engaged the idle is rough, but once the a/c engages the idle smooths out. it's still a little rough but not as bad as when the a/c is off.

 

Also, does the vapor canister need a cap? I could have sworn it needed one but there isn't one on the truck. I've looked online and the vapor canisters i've seen online don't have them. on my truck there is one line that is going to the vapor canister port on top and then other port is just open.

 

Then vapor canister is not hooked up.

There is a vacuum canister and a vapor canister, both will have/need 2 vacuum hoses connected.

The vacuum canister has a hose to the intake, this inlet will have a check valve so air can be sucked out(creating a vacuum), but can't flow back, losing vacuum.
And a hose to the climate control, EGR system and other vacuum systems that need vacuum when engine may not have a vacuum.
So it is a vacuum storage container.

The vapor canister is for the EVAP system.
It uses engine vacuum to create low pressure(vacuum) in the fuel tank so gas fumes do not pollute the air.
It will have a hose from the intake to a Solenoid and from solenoid to vapor canister(charcoal canister).
And it will have a hose from vapor canister to the fuel tank.
Computer operates the solenoid, opening it up to use engine vacuum to pull gas fumes from tank thru charcoal filter and into engine.
There is often a Pressure sensor on this system as well, since EVAP is part of Emissions system it must always be working or you will get a Check Engine Light(CEL)


Neither of these systems would be "vented"

 

Where are both of these located? I think I am talking about the vapor canister it looks like this pictured.. there are two lines going to it. one goes to the throttle body. the lines are cracked. and the other goes to the fuel tank i assume. the two big ports on the top (one is capped and the other is open)

 

Yes that is the EVAP systems charcoal canister or vapor canister

Caps are fine to keep crud out but not required, there is a valve in there in case pressure should build up, "atmosphere vent"

 

and both the 1" ports should be capped correct?

 

It is not really a "cap" more of a cover to keep debris out
Tubes should be sealed at the bottom with a valve

 

fixed the vac lines coming from the canister, but it's still doing it.

when I first start the truck, it will rev to the normal idlng speed then a second later it will bog down. The battery gauge will fall, and it only does it for about 1 or 2 seconds then the truck goes back to normal idle and everything is normal. It does this every now and then, only when I am not actually pressing the gas pedal. When ever I am actually driving, it seems perfectly fine. The CEL comes and goes as it wishes.

 

bump

 

For people with problems like this. I tested my IAC and the voltage was exactly what was supposed to show. But I went ahead and changed it anyways. that seemed to be the problem. thanks guys

 

Thanks for posting the fix.