Code 172 Mustang 1994. Can it be the egr ?

gdushkin

New Member
Nov 6, 2019
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Massachusets
I have a 1994 5.0. I pulled the codes this morning and one of the codes was 172 running lean. How can I remedy that? I just checked vacuum leaks and fuel pressure everything seems to be working normally I don’t have an egr or an air injection pump. I had my egr plugged up by a plate with a gausket that I cut out of a piece of aluminum (it seems to seal just fine) . But I had the egr plug plugged by an eliminator plug from eBay could that be a problem or am I looking in the wrong spot.
 
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Are your O2 sensors in good shape? If the O2 sensors have gone bad and the voltage sticks low, it might be giving a lean feedback signal even though the system has adapted super rich. You might want to pull a spark plug and check the color to see if you're burning around stoich (tan) or if they're black.