Mattman928

I have a question about the running modes of the LH brain. I am judging open loop vs closed loop by the watching the A/F meter hunting. I assume that if it is hunting then it is in closed loop, and if it sits is one spot (rich) then the brain is in open loop. Is this correct?

In a 1990 GT what can cause the LH to stay in open loop mode?

- Temp II failure
- WOT switch engaged

Anything else?

Rich9928p

Anything else? ..... how about a failed LH fuel injection module.

michaelathome

O2 Sensor disco'd or bad maybe?

Michael

Louie928

I didn't fully understand your question. You said "stay in open loop" then described how it acts in closed loop. There are conditions of load and RPM that will cause open loop even at less than WOT. Does it stay open loop no matter what all the time, or only during certain conditions.

Mid to high RPM and less than WOT will cause open loop as will high load at less than WOT. A bad MAF, or too high fuel pressure, or anything that causes the mixture to go beyond the ability of the LH to control it, i.e., >+/- 20% from stoic will keep the closed loop system from functioning.