Running rich on idle

[morpheus]

Hi..my car is running. rich on idle 11.8 ..even when the engine heats up..ive did a boost leak test no leaks..whats ur opinion guys..thks

 

[lukep]

Engine coolant temp sensor on the thermostat housing two wires I'd say.

 

[morpheus]

Ok tested the cts its fine...what would happen if i disconnect the 0 2 sensor when the engine on..will there be a change in idle...will the ecu fuel richer instantly..when i disconnect mine nothings happen...

 

[weeJohn]

Could be the O2 sensor, it should read about 0.45 volts on idle. If its giving no signal back it will add more fuel.

If you have a aftermarket FPR, uprated fuel pump or different injectors, they can all cause the rich idle as well.

 

[morpheus]

Could be the O2 sensor, it should read about 0.45 volts on idle. If its giving no signal back it will add more fuel.

If you have a aftermarket FPR, uprated fuel pump or different injectors, they can all cause the rich idle as well.

I get no voltage on the 02 sensor pluging. When engine on...is that normal?

 

[morpheus]

Change the o2 sensor this morning..still 11.5 on idle..any other tips guys

 

[thefalls]

There used to be an issue where the ecu thinks its in cold start mode all the time and thus running rich all the time.
Read it somewhere.

 

[weeJohn]

Change the o2 sensor this morning..still 11.5 on idle..any other tips guys

What voltage are you getting back from the O2 sensor now?

 

[morpheus]

What voltage are you getting back from the O2 sensor now?

Same results with both sensors 54 to 58 milli volts ..on the pluging and the same also on the diag port ox and e1.

 

[azerty]

as weejohn said. it should be around 0.5volts at iddle.
anything lower, your ecu will think you are running lean/cold and will constantly add fuel

 

[weeJohn]

The 1 wire sensors do take a little time to warm up to operating temp, they can also fall out of their working temp range, if you take it for a run to get warm air out the exhaust does it still read as low a feedback?

Worth while checking the connection from the sensor to the loom wiring, it tees off below the diagnostic port from the wire coming from the plug to the ecu, so what its reading at the diagnostic plug is what its reading at the ecu.

 

[morpheus]

Check continuity from sensor pluging to diag port 0x1 .its ok..will have to check from diag port to ecu now.hope that is my problem..

 

[morpheus]

Also does the O2 generates its own voltage or its the
ecu that send the voltage and reads back..

 

[weeJohn]

It generates the voltage. Also worth remembering that it is based on a free air calculation as well, if you have an exhaust gasket leak that allows air to be sucked into the system before the sensor, readings will be affected in a way that causes it to over fuel.

I can only assume your wideband is in a different location to the stock sensor or they would be reading much the same.