1FZFE rough idle, stumbles, stalls...

[dirtboss]

thanks, that is very informative,

 

[mmm635]

The finer details have been up for debate but,

Closed loop is where the ECU adjusts fuel trim according to the readings from the front O2 sensor.

Open loop is where the ability to adjust the fuel trim is beyond the ECU's ability so it runs with a constant value instead of adjusting it.

Limp mode is where the ECU has determined a sensor fault and runs a pre determined set of variables which usually means a rich condition allowing the driver to "limp"home without damaging the engine.

Yes, but in a closed loop system the down stream sensor sends the feedback to the ECU as well for the emissions output, and does the computations from data up and down stream. Yes, the pre-cat sensor is what actually detects a lean condition (in a situation of a vacuum leak) and tells the ECU to add more fuel, causing the mixture to become rich and run poor. However, the post-cat sensor can have an effect in the overall maps trying to maintain proper emissions output within the factory set parameters.

 

[Gumby]

The down stream O2 is there to monitor the catalytic converter efficiency. Without the need for emissions monitoring on OBDII vehicles there is no need for a downstream O2.

However, if the vehicle is an OBDII compliant vehicle, if there is a problem with the downstream O2 the car may not enable the monitors correctly and may ignore certain information.

 

[RescueU]

Oh and to update my issues, I found a very small leak in the heater hose above number 6 and evidence of a puddle around the spark plug seal pulled it and dried up what little moisture I could see, tighten up the clamp on the hose and now it runs fine . new code though a knock sensor is broken I might have broke it when I did the fuel filter.

I just found the same red pool of coolant at #6 plug wire boot, and my '97LC has been running at a horrible state throwing P0306 codes at pretty much any amount of throttle applied. I'll tighten up the heater hose clamps and dry the area out to see if this could be a root cause for the recent rapid degredation. Good info!

 

[Romer]

Woody - how has it been running since you reconnected the O2 sensors?

 

[Brayden3223]

Hey guys I know this is a old forum but it seems to be the most informative one for my issue so far, I have identical issues to what you seemed to have had, just confirming, it was the O2 sensors that was creating a high idle randomly and also causing the car to run rough, misfire and stall?

 

[smorkington]

I had similar symptoms with my 93 1fz. No codes, stalling out, very rough idle, it could only stay running if you floored it. I assume it ran better when given some throttle because the timing has some sort of electronic advance. Embarrassingly enough I was just off a tooth on my distributor :\