Knight4

I've seen references in this forum to the fact that the ECM doesn't use certain sensors at different times (i.e. startup, engine code, engine hot, etc.). I've got an FSM and don't find any reference to this information.

Can someone either point me to where this information can be found in summary (I know there are bits and pieces floating around the forum) or outline here what happens at what times?

My running problems (stalling/unsteady idle while engine is cold) all start to occur about 30 seconds after starting the engine and disappear once the engine gets up to operating temp - but not automatically...it generally means the car has to stall about when it reaches operating temp and then after re-starting it will run great! Like it has to reset a sensor or something. Or...if I arrive where I'm going before the engine reaches operating temp and I let it set for a few minutes, it will "heat up" whatever sensor needs to be warmed up and when I re-start the engine again, all will be good!

I'm hoping that by better understanding which sensors are watched at what times, I may come closer to solving this problem once and for all. This seems to be so closely related to problems that many of us have and to which there just doesn't seem to be a good answer.

My best guess at this point is that this seems to be related to the Heated O2 sensor - which I understand goes from open loop to closed loop (or vice-versa) after the engine has run for about 30 secs or so. But I don't understand what "closed loop" and "open loop" mean. I also don't understand why the problem would go away after reaching operating temp if it is in fact the O2 sensor.

Perhaps this would be good information to have in a sticky?

Knight4

^^ bump ^^

Anyone want to take a shot at this? Or point me in the right direction?

Jeff92se

iTrader: (82)

Does go into fast idle when you first start it?? I would check the water temp sensor (red). Connector and sensor itself

Knight4

Yep, it momentarily goes into fast idle (approx 1200-1400rpm) when starting, then drops to a more normal "cold" idle (600-900rpm, depending on how cold the ambient temp is and whether the engine is already warm or not) once it figures out what it's startup parameters are. Nothing seems amiss when I initially start it, it's only after I let it idle for a few seconds and then start driving that the problem starts - and only if the engine temp is below 185.

I've already replaced the coolent temp sensor and thermostat.

What I'm really hoping for here is someone to help me understand what sensors are ignored/read until the engine reaches operating temp, or what happens to the sensor picture when it does reach operating temp.

slimhall

good question can anybody answer that q

Greeny

iTrader: (43)

Use the noobie thread at the top of the forum..Give details, lots of details..