Its been a while since i have been on here and i just wanna ask a few questions about these engines. Open loop and closed loop. What sensors are being read during open loop? My car runs best, as in no stumbles, hesitations or the ill fated 5,000 rpm stumble that resembles a machine gun. the only thing that a mechanic can see is that there is a slight burn mark on one of the diods on the mass air. and that the right oxygen sensor isnt doing a complete cycle, but at WOT the O2 isnt read supposedly. I know that the mass air isnt reading at start up.. is there any other sensors that arent reading during this time?

The car also at the same time has a problem that if ya sit with the car running for like 10 min or less actuall that at 5 grand it will break up losing power (backfiring) and if run that way the car reaks of gas.... could there be problems with fuel ratio. it does like to resemble a diesel on take off at wot esp. when programed

should i start at the mass air sensor? any opions, or answers welcome...

and wiil a 94 mass air work on a 95?

thanks jason

 

There are only two differences between open loop (cold start) and closed loop..... 1) in open loop the O2 sensors are not capable of producing a signal, so they are ignored, and 2) since there is no input from the O2 sensors, "learning" is diasabled - the long term fuel corrections can not change. ALL the other sensors are used, including the MAF sensor. Why wouldn't they use the MAF on cold start? It is a precision instrument that works as long as it has the correct power supply. There is no "warm up" period. There are different tables used to set the target A/F ratio on cold start, but its not a matter of ignoring sensors.

When you go "WOT" (actually, when you exceed the values in the table of throttle position % vs. RPM), the PCM again ignores the O2 sensors, and disable learning, but GM has chosen to call this "power enrichment" (PE) mode, and not open loop.

Point is, the only thing different between closed loop and the other operating modes (open loop, PE) is the O2 sensors and learning enable.