My buddy got an A/F gauge for his car. Before he hooked it up on his, I wired it in on mine quickly just to see how i was running. When I first start the car and its cold, it stays right in the stoich area....but after the car warms up, the gauge flies back and forth from all the way lean to all the way rich and back and forth etc....is there something wrong with my car or is this normal? Could it be my spark plugs (77,000 miles on them, but being changed in a couple weeks)?? Thanks

 

Thats normal for the values to fluctuate a bit. When your WOT is what you really need to pay attention to.

 

THe A/F gauge uses a stock O2 sensor to gether its reading. When your engine is cold the O2 sensor isn't working yet (needs heat to work), that's why your reading is stable and "centered". The stock O2 sensors are very inaccurate at any reading other than 14.7 AFR, therefore the gauge will be inaccurate. The O2 signals should bounce between rich and lean.

 

Okay, because at an idle after it warms up, the thing just goes back and forth non stop from lean to rich.