Recently purchased a '93 Bronco w/5.0.

If the Cat were hollowed/burned out, what code would be thrown behind the CEL?

 

These are the codes I'm aware of for exhaust related CELs for 92-96 s

• PO401: Insufficient EGR Flow
• PO402: Exhaust Gas Recirculation (EGR) Excessive Flow Detected
• PO410: Secondary Air Injection System Malfunction
• PO420: Catalyst System Efficiency Below Threshold (Bank 1)
• PO421: Warm-Up Catalyst Efficiency Below Threshold (Bank 1)
• PO430: Catalyst System Efficiency Below Threshold (Bank 2)
• PO431: Warm-Up Catalyst Efficiency Below Threshold (Bank 2)

 

Ok thanks ZombieSlayer.

I'm trying to diagnose a 173 CM code.
Had a fellow tell me that the Cat was probably hollowed/burned out.
The thing has a Cat and a muffler and is still louder than my 351 running a Cat only.

I've replaced MAP, ACT, and o2.
ECT checked good.

Disconnected battery overnight to clear all adaptive strategies.
Same result.

There are no KOEO codes.
The 173CM will set every time when the engine comes up to operating temp.

 

This vintage Bronco has no way to measure converter efficiency. The single O2 sensor is before the converter.

The codes you listed are for OBD-II vehicles. The OP's truck is OBD-I.

 

A gutted or even missing converter will not trigger a rich code.

Have you checked the fuel pressure?

Age of the O2 sensor? Is it covered in oil, grime, etc.?

 

Have not checked fuel pressure. (no tool for it)
Did check for fuel in FPR vacuum line. (none present)

o2 sensor is new. (Bosh from Autozone)


Edit = I have obtained a copy of the Pinpoint test. Will proceed down the list today.

 

You can rent a fuel pressure tester at most auto parts stores.

 

Following the steps in the Pinpoint test ....

ASSUMING the fuel pressure steps all passed ...
The next rungs of the ladder have all been done and passed.

The truck is indeed running rich.
Smell and/or black smoke verifies.

Seems logical to me that it indeed has to do with fuel pressure and/or injectors.

Thought maybe I'd run some injector cleaner thru it just to see what, if anything, happens. But to be honest I'm about sick of screwing with it. I have a mechanic that I trust. Was just hoping to save some $ and gain some knowledge in the process.

Thanks for all offered assistance! :-)

 

That's what happens when you skip a step in basic troubleshooting, your wallet and patience pay the price.

 

Update = Fuel Pressure Regulator

Problem solved.
Thanks for the help folks!

 

Glad to see you found the issue. Thanks for the feedback.