Join Date: May 2018
Location: Austin, TX USA
Bronco Info: 1994 Bronco XLT 5.8L E40D
[RESOLVED] code 334 & 172 - EGR closed voltage higher than expected
Guys, I really need help with an incredibly stubborn Code 172 & 334.
I suspect the 172 is just a symptom of the code 334.
No mods that I know of.
Just bought it from a car lot a few weeks ago, issue has been present from day one.
Symptoms I get:
Runs smooth till it warms up.
Then when I stop at a light, the idle might suddenly drop from ~1k down to ~500 RPM and stumble.
Then pop back up to ~1k for a moment, then drop to ~500 again. And occasionally dies.
When this happens, sometimes the tranny will suddenly start shifting at really high RPM's with whiplash effect.
Things I've replaced in the last two weeks:
-EGR Vacuum Regulator Solenoid
-Coolant Temperature Sensor
-Idle Air Control Valve
-Throttle Position Sensor
-Fuel Pressure Regulator
-ACCEL Distributor Cap
-Ford Racing Spark Plug Set
-EGR Valve Position Sensor
-Replaced all vacuum hoses
-Cleaned PCV Valve
-Cleaned Throttle Body
Troubleshooting steps I've taken so far:
-Plugged Vacuum tester into EVR top line going to EGR and it held vacuum.
-Plugged Vacuum tester into EVR bottom line going to solenoids and it held vacuum.
-Applied vacuum to EGR while engine was running and the diaphragm moved and engine idle changed.
-EVR 12V pin shows -12V on my multimeter.
-Shorted EVR's pin 33 to ground while engine running and the engine died.
-Applied vacuum to vacuum canister AMP with MAN disconnected. It holds vacuum fine.
-When I do the KOER code test, the EGR does not move.
-Hooking a vacuum gauge inline with canister AMP shows "green" levels of vacuum (good).
-EVP shows 5v at pins VREF and SIG RTN.
-EVP shows ~3700 ohms at pins VREF and EVP and it goes down to ~350 when I apply 10hg vacuum to EGR.
-Disconnected IAC. Applied vacuum to EGR and engine RPM's stumbled as expected.
-Put Vacuum tester inline at EGR and raised engine RPM's, the vacuum does not register anything at all.
-I have yet to see the EGR move except for when I manually apply vacuum to it.
I'm sure I've forgotten a few things.
Any and all help would be appreciated!
If there are any sensors I should try replacing, then I can do that too.