I have an idea but I'm not 100% sure. I think it means A/F ratio b/c yesterday my teacher told me that 0% fuel trim is stoich while anything above is lean and anything below ( - ) is rich. But what exactly does "fuel trim" mean. Is it A/F ratio? thanks
peanut23536
Favorite Answer
It's how much the computer is adding or subtracting to keep the engine running at the proper efficiency. For example, if you had a vacuum leak, the fuel trim would go up to compensate for the lean condition. It would go up until it counters the vacuum leak. The computer monitor the O2 sensor to determine how rich/lean the engine is running.
toadyboy
fuel trim is either above or below the extra above or below zero
Anonymous
confusing thing. lookup from yahoo. this can help!