In need of assistance my 351 has very high emission readings on hc and co nox is good have changed temp snsor and o2 sensor run the scan and it reports code 173 running rich bank 1 does anyone know what will cause this to run rich it is port injected new plugs and wires complete tune up has been done ,the o2 snesor is located before the cat need some direction thanks to all who help toby
Check for vacum leaks or a vacum hose off also make sure spark plug wires are making contact on the exaust mainfold then run a fuel treatment to clean out the banks high octane fuel usually does the trick but you can also use alcohol, make sure you run, drive it for a couple of days before you emission it. If that doesn't work you are going to have to change that cat. Good luck.
That vintage had problems with fuel pressure regulator failure. If it fails, it will go rich. Pull the vacuum hose. If you have fuel in the vacuum hose, it is definitely gone. If not, check fuel pressure as it may fail without leaking. They were the subject of a recal a few years back. That campaign is done. The FPR is not all that expensive. Only any Allen key is needed to change if your fingers have an extra joint.
Good luck
Lugnut
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