Hi all,
Does anyone know the volt readings for the front o2 sensor on a 95 wrx 2.0L turbo. Im currently struggling with high idle and the car running rich. Ive cleaned and tested everything else i.e. iacv...tps...maf etc and everything ok. I put a voltmeter on the o2 sensor and the millivolt readings are all over fluctuating from say in range from 23 ish to 100 ish. It just shows loads of different numbers in that range. Anyone know the true readings? And does this sound like the cause?

The other prob is my car takes ages to warm up. I have just replaced a broke thermostat to a new one but still a long time to warm..it does now stay warm when driving as it didnt before.

Any help appreciated...ive had this car (first scooby) a few months n is costing me like mad. Just need an mot so i can get rid!

 

[QUOTE=steven bass;10999673]Hi all,
Does anyone know the volt readings for the front o2 sensor on a 95 wrx 2.0L turbo. Im currently struggling with high idle and the car running rich. Ive cleaned and tested everything else i.e. iacv...tps...maf etc and everything ok. I put a voltmeter on the o2 sensor and the millivolt readings are all over fluctuating from say in range from 23 ish to 100 ish. It just shows loads of different numbers in that range. Anyone know the true readings? And does this sound like the cause?

The other prob is my car takes ages to warm up. I have just replaced a broke thermostat to a new one but still a long time to warm..it does now stay warm when driving as it didnt before.

Any help appreciated...ive had this car (first scooby) a few months n is costing me like mad. Just need an mot so i can get rid!

Forgot to mention...when the car registered temp the idle didnt fall and also when i disconnected the o2 sensor there was no change to the running of the car at all!

 

O2 sensor ocsillating means that the closed loop fuel control is working absoluetly fine - but does not guarantee that once you put your foot down and are in open loop that it doesn't go rich due to a dodgy MAF reading or ECU temp sensor etc. If you have a high idle and have cleaned the Idle control valve then one likely reason for the high idle and running rich would be ECU temp sensor. When not getting good reading it would revert to something safe and similar to COLD startup.

Best read any fault codes from it and see what they say. Search for how to do this as I don't have a link handy.

 

Stupidly i tested the wrong sensor! now i found the right one i tested it. I ran the car for 5 mins and the readings showed .24v and going down. It did go up from time to time then slowly went back down. im guessing the o2 is faulty. Plus i did the ecu reset and i showed code 32 (o2 sensor) but this flashed maybe 10 times then went to normal flashing as if everything was ok?!

im going to go for a drive then test it again.

I was also wondering about the temp sensor to ecu. I thought it could be telling the ecu its still cold?
The wierd thing is my temp gauge gets to normal operating temp after about 20 mins of just idling and never goes above half way even after an hour of running on the drive. I have a brand new thermostat in and filled the coolant correctly. could my temp gauge sensor be faulty or could it all be linked together.

so maybe i have to faulty temp sensors.....likely o2 sensor too........or there is actually something keeping the engine cool?? could the coolant around the sensors actually still be cool?

is there a way to test the temp sensor to ecu? volts or ohms maybe?

just so you know my idle always stays at 1500 no matter how long the car has been running or what the temp gauge says

 

The O2 sensor *could* be caused by your driving without it connected. Its output should oscillate in the range 0.1 and 0.8 volts, but will only do so when it is hot. If its internal heater is broken on idle it might not get hot enough to work correctly. If your O2 code came back after reset it's possible its broken, but I thought the ECU took a long time to detect an O2 sensor failure normally. I'm not saying its not broken, but don't bin it just yet as a faulty one wouldn't normally cause a high idle anyway.

Scoobies like most cars have separate temperature senders for ECU and dashboard, so its possible that the ECU one could be giving wrong reading but the Dash one to work. See https://www.scoobynet.com/general-te...mp-sensor.html to find it.

 

well the only code i was getting was o2 but like i say...after it flashed that code a few times the flashing went to normal as in no prob. I wasnt driving with the sensor disconnected i just unplugged it to test it, and on unplugging it didnt alter the running of the engine at all. I just went to test the ecu temp sensor and found it a bit fiddly so being in a race with the sunlight i decided to have a go tomorrow but....the damn connector broke grrrrr!!! i can repair it luckily. Now the temp sensor is disconnected im gettin a constant cel and my rad fans work. The car even after an hour of idle never thought it was hot enough for the fans to kick in. So im starting to think the high idle is temp sensor. I just dont know what the temp sensor readings should be, does anyone know? and the sensor doesnt have to be connected does it?

 

I can't find any specs anywhere for it. Often (for other makes) they are 1k Ohms at about 25 degrees C, high when colder and lower when hot. To be honest if a code came up and fans came on with it disconnected it sounds like its probably working fine - they tend to fail open circuit but if so pulling the plug would have made no difference.

Have you actually tried to clean the Idle control valve? Check that its not sticking? Also check for any air leaks post throttle, which would cause increased idle, and rich on boost due to metered air escaping not going into the engine.

One last thing is if you have changed the coolant because you changed the stat, an air lock might affect the temperature the ECU "see's" - but normally you would see your dash gauge do something similar because they are close to each other. Worth checking you can't fill with any more water using the hose which joins the header tank from the turbo - best way to fill these without getting air in the system.