Persistent Code 84. (1987 Ford Bronco II Auto)

[Nelson and Hudson]

TLDR: The engine has the vacuum source, but the computer is sensing that the EGR still isn’t opening correctly during the test.

(1987 Ford Bronco II Auto) I have been trying to get my smog test passed for the last year. Could someone help me identify the issue?

In 2023, when I first had to get smogged, it failed at first, but then passed.
Smog Check #1 — 2/18/2023

• Visual inspection passed, functional check passed, ignition timing passed, and fuel evap controls passed, but the emissions test failed, and the inspector noted: “Check EGR”.
• The raw numbers showed the 15 mph and 25 mph test results passed, so this first failure looks more like a system concern than a simple tailpipe outlier.
• At this point, EGR was already on the suspect list.

Smog Check #2 — 2/28/2023

• Everything passed, including emissions, ignition timing, and fuel evap controls.
• This is important because it shows the truck can cleanly pass when the system is behaving properly.
• The later failures are therefore not random; something changed or degraded afterward.

When it was time for the next test, it failed badly.
Smog Check #3 — 7/8/2025

• This was a much worse result: visual inspection failed for tamper, functional check failed, emissions failed, ignition timing failed, and fuel evap controls were listed as disconnected.
• The diagnosis again came back as EGR not functioning properly.
• I also got a list of things to inspect: TPS, catalytic converter, coolant temperature sensor, and oxygen sensor.

What I Fixed

• I adjusted the TPS to the proper voltage range of 0.96V to 4.3V.
• I repaired electrical faults and grounds.
• I fixed the O2 sensor connector.
• I changed the oil and gapped the plugs properly.
• After those repairs, the surging issue was largely gone.

Went to go get it resmogged, still failed, but less so.
Smog Check #4 — 10/17/2025

• Visual inspection passed again, functional check passed, ignition timing passed, and fuel evap controls passed, but emissions still failed.
• The diagnosis shifted slightly to: vacuum checked within spec, but EGR may not be functioning properly.
• The vacuum supply looked okay, but the EGR still was not doing its job.

So from this point, I knew I had to go through the EGR System.

(Vacuum routing for vehicle)

1. EGR Valve 2.EGR Vacuum Regulator (EVR) Solenoid 3. EVP Sensor

• I identified the EVR porting: bottom port = vacuum source from the EGR tube/manifold vacuum side, and top port = EGR valve side.
• I measured about 20 mmHg at the tube feeding the bottom port of the EVR while the engine was running, which supports that the vacuum source is present.
• The EVR coil resistance checked around 50 ohms, which suggests the electrical coil is not open.
• I measured that the EVP sensor is getting 5V, ground is solid, and the sensor wire is giving off ~3.18V
• When I compared it with a new EVP, it gave the same reading.
• When I use a vacuum pump on the EGR, I can hear it move
• The Vacuum Reservoir holds a vacuum.

Where It Stands Now

• The truck has shown it can pass smog when the system is right.
• I have already ruled out or improved: TPS, grounds, O2 connector, plugs, timing, and vacuum supply.
• The remaining focus is on the EGR control path, especially whether the EVR is actually sending vacuum to the EGR valve when it should.

Code 84 is persisting regardless.:”84(O.R) Solenoid/ circuit fault for Electronic Vacuum (or Voltage)Regulator (EVR) Exhaust Gas Recirculation (EGR) cutoff solenoid or Exhaust Gas Recirculation (EGR) solenoids, whichever is present”

Code 32 (memory) (Test): “Pressure Feedback EGR or (EVP) lower than normal”

Code 33 (memory) (Current): “EGR Valve Position (EVP) was out of range”

TLDR: The engine has the vacuum source, but the computer is sensing that the EGR still isn’t opening correctly during the test.

 

[sgtsandman]

Usually, when there is an EGR problem, the valve is clogged or stuck. You could try cleaning out the EGR valve. Sometimes that works. It just depends on how fouled up it is inside. If it's stuck, you might be able to get it to break free with some penetrating oil but It might just be easier to just replace the valve. It's been a good while since I changed one on one of my vehicles but I seem to remember them not being all that expensive.

 

[Nelson and Hudson]

Usually, when there is an EGR problem, the valve is clogged or stuck. You could try cleaning out the EGR valve. Sometimes that works. It just depends on how fouled up it is inside. If it's stuck, you might be able to get it to break free with some penetrating oil but It might just be easier to just replace the valve. It's been a good while since I changed one on one of my vehicles but I seem to remember them not being all that expensive.

EGR valve moves freely; it's a new EGR.