ok a few weeks ago, i was at a friends house and we decided to clean our intakes and check the ignition timing. the next day i noticed that my O2 sensor was unplugged so i plug it in and disconnected the battery to reset the ECU. So a week passes by and i finally notice the irritating dead spot around 2500-3000 rpm(which happens to be a lot worse at cold start). I usually shift in that range when im cruisin, so having a dead spot there really sucks. a couple weeks pass then i finally realize that the dead spot started to occur when i plugged the O2 sensor back in. so i immediately disconnect it in the morning and drove around the neighborhood. Drivability was MUCH better!!! No dead spot at all!!! even when the engine is cold. And a lot less jerking. I was so irritated with the dead spot that i was about to dish out $70 for a new o2 sensor but since i found this solution, im gonna put it off.

mate were is the bit to disconnect the 02 sensor ??

excuse me mate? are you talking about the plug for the O2 sensor? just trace the wire back half a foot from the sensor. its not hard to find.

are you kidding me? ill do it if it doesnt turn the check engine light on... anyone else done this??? :confused:

All I know is if you disconnect your O2 sensor your gas mileage will be horrible.

i am only posting this to inform sr20deforum what solved my problem, you may also do it at your own risk. as for my car, no i didnt get a check engine light. My gas milage has bee 26-27 mpg with the disconnected O2 sensor.

Originally posted by Ben92SentraSE-R
All I know is if you disconnect your O2 sensor your gas mileage will be horrible.

Thats because the ECU is mostly switched over to open loop maps for safety reason RICH. This might not be a bad idea as it would be a lot more easier to tune a SR20DET in open loop not having to worry about the lean mixtures in closed loop operation or closed loop-part throttle full boost situation or just plain cruising.

charlie2020- can you elaborate more on this open loop tuning idea? If I remember correctly, open loop ignores ignition timing and/or fuel maps. How can you tune well for performance and good gas mileage with this/these things out of the equation? Aren't these things what make EFI work well?

Originally posted by Ben92SentraSE-R
charlie2020- can you elaborate more on this open loop tuning idea? If I remember correctly, open loop ignores ignition timing and/or fuel maps. How can you tune well for performance and good gas mileage with this/these things out of the equation? Aren't these things what make EFI work well?

Ben92SentraSE-R think of closed loop as bad for performance exspecially on turbo cars, the only reason for closed loop is emissions and gas milage other than that it is a performance and potential engine killer, I'll give you and example full boost+part throttle=closed loop=STOICH fuel mixture=blown engine. Think of closed loop as the STOICH loop and open loop as the RICH loop or performance loop as this is were all high performance cars make there power. The ECU doesn't care if you are at full boost+part throttle=closed loop (LEAN) it will only go into open loop (RICH) when you crossed that threshold of throttle percentage. If your not in open loop at full boost you are asking for trouble put the pedal to the floor. The one question that we need to be asking is at what throttle position % does it switch into open loop.

http://members.shaw.ca/costall/ECUprimer/ECU_ch3.html
[QUOTE]When people talk about open or closed-loop operation on DSM ECUs, they are invariably talking about the specific function of fuel delivery[QUOTE].
[QUOTE]To sum up, closed-loop operation means that the ECU uses the MAS information to determine an initial amount of fuel to deliver. The oxygen sensor signal provides feedback to help correct this fuel amount for variations in the individual sensors and engine. This leads to better fuel economy and emissions, as there is very little wasted fuel. Closed-loop operation occurs when the engine is running at a near-constant speed and a near-constant throttle position.[QUOTE]

http://www.sdsefi.com/techtune.htm
[QUOTE}When the system is in closed loop, the ECU looks at oxygen sensor voltage to correct the air/fuel ratio automatically to around 14.7 to 1. This is mainly for emissions. It is dangerous to run most engines hard in closed loop mode because the air/fuel ratio is too lean at high hp levels. For the purposes of simplification, we will assume that the closed loop function may be used for the part throttle conditions to satisfy emission requirements only. If emissions are not a concern, better driveability and fuel economy is often obtained by leaving the system in open loop or programmed mode under all conditions. Open loop mode is when the system is operating off the values programmed into the ECU's memory[QUOTE].

http://www.sjmautotechnik.com/10vo2sen.html
[QUOTE]When the engine is first started when it is cold, the engine will briefly run for 1 or 2 minutes in open loop operation based on the "basic" idle mixture setting in the CIS Fuel Distributor/Air Flow Meter assembly and by the duty cycle programmed into the ECU.[QUOTE]
[QUOTE]If the O2 sensor wire is disconnected with the engine running, the ECU normally has a 0.450 V (+/- 0.050V) reference voltage on the ECU wire connecting to the O2 sensor. The ECU will switch over to a basic idle mixture setting (freq valve duty cycle set to 50%) with the O2 sensor disconnected.[QUOTE]
[QUOTE]If you suspect the O2 sensor is causing a running/drive-ability problem, you can temporarily disconnect the sensor and drive the car to see if the problem still exists. The system is designed to operate without the O2 sensor connected and the engine will run fine assuming the other systems/components are functioning properly and the basic idle mixture is set correctly (upstream idle mixture CO% is set between 0.6% to 1.2%). Please note that disconnecting the O2 sensor will store a fault code in the ECU.[QUOTE]

http://www.g-speed.com/pbh/afr-o2.html
Most ECM operates in two mode - close loop and open loop mode. Close loop means the ECM monitors the oxygen sensor and tries to maintain stoichmetry in order to ensure good emmision performance. When you go wide open throttle (gas pedal floored) ECM goes into the open loop mode which it ignores the oxygen sensor output. In open loop the ECM uses the fuel map programmed by the manufacture. These valves are more performance oriented and most engines make good power around the AFR of 12.5-13.0:1 or so. Honda motors are more efficient than most demostic cars, I have heard people think Honda motors like 13.0-13.5:1. I'm not really sure about that, but all we need is for somebody to have a wide range oxygen sensor setup and a dyno then we can know for sure.[QUOTE]

^^^^he is talking about NA cars not turbo as 13.5:1 would be bad for a turbo car but not for a NA one^^^^^^

I have more but I think you can see the patern.

Hope I elaborated enough, and hope you learn something new.

So its ok to d/c the o2 sensor ... to test ?

it will not damage anything ?

yes it is ok

Wow mate done it started engine when it was way cold ie in the morning.

No since of BOgging @ all thanks mate.

I will buy a new 02 sensor now.

Originally posted by kamikaze
Wow mate done it started engine when it was way cold ie in the morning.

No since of BOgging @ all thanks mate.

I will buy a new 02 sensor now.

I hate to rain on your parade but when you start the car in the morning when the temp guage reads colds you are in open loop until the car comes up to operation tempature and/or the Air Regulator Valve has timed out also known as the cold idle bypass valve this valve allows metered air to bypass the throttle plate to aid in cold start-up situation/high idle. Now did you also drive the car? or just let it idle? Its a little unclear from your reply.

Oh soz mate.

I took it for a drive.

normally I notice it starting to bog as soon as i get out of the drive way.

Nothing at all :) was fine.

Originally posted by kamikaze
Oh soz mate.

I took it for a drive.

normally I notice it starting to bog as soon as i get out of the drive way.

Nothing at all :) was fine.

Good to hear.;)