Unplugging O2 Sensors On R33Gtr

[livewire]

Hey guys, just wondering if its possible to unplug the o2 sensors without causing damage to find out whether car runs fine without them in use to find out whether they are the cause of a surging problem while cruising on flat road at 100-110 km/h and slightly rough idle for 30-60 seconds before coming good. Dont want to go replacing them if theres a way to diagnose whether its them playing up or not first.

Running factory ecu by the way

[XKLABA]

Yeah you can unplug them next to the inlet of the rear turbo is two plugs, it will just make car run rich which is not to bad for engine

[MagicMikeZ32]

you can test their operation with a multimeter

[livewire]

Thanks guys. Changing spark plugs this afternoon so if that doesn't solve the hesitation/surging problem I'll try unplugging the o2 sensors and take it for a run to eliminate them or get confirmation i need a new set if it runs fine without them in use. Otherwise next step will be afm's.

Another question... If timing was changed slightly to suit power fc and then factory ecu was put back in, could that have anything to do with it? I've been told it shouldn't but Im not so sure

[XKLABA]

If you moved the timing from where it was with stock ECU then when you put the stock ECU back in it needs to be put back to where it was

[Ben C34]

Timing being set correctly is the first step to getting anything right.

[livewire]

Well there you go. Youd think the place who tuned the power fc would have suggested that after i rang them when it started playing up asking if that could be the issue or if it needed to be done but said no it should be fine :-/ better find someone with a timing light then !

[livewire]

Problem found thanks guys. Simply unplugged the oxygen sensors one at a time and front sensor is the issue. Idles smooth with it unplugged so for anyone with similar symptoms try that first!

[livewire]

Changed spark plugs first with iridiums and started fine and idled fine while cold. I let it idle till it was warm as it was getting to nearly 2/3 on the temp gauge it started to idle rough like it was last time I drove it. Also changed the fuel filter and hasn't it don't its job since it was last changed. The black shit that was coming out of it was unreal so good thing I decided to change it anyway. After that the idle was still rough so figured i'de try unplugging the o2 sensors one at a time. unplugged rear one first and waited 10 seconds and no change. unplugged the front one waited about 5 seconds and low and behold the idle corrected itself and was purring like a kitten again, plugged it back in and after about 5 seconds.... idling rough.

Now I haven't yet been able to take it for a drive on the open road to see if the surging has gone away with the o2 sensor unplugged at between 100-110km/h where it was playing up before but fingers crossed once I put new o2 sensor in, it'll solve that issue too as it started at the same time the rougher idle did.

Thanks for everyones help and suggestions

[blind_elk]

AFAIK, the ECU ignores the O2 sensor(s) at idle and on a cold engine, so I am perplexed that unplugguing either of the sensors made any difference.

You may well have fouled the plugs by letting the engine simply idle to warm up. Engine runs rich when cold, best to drive it to warm up the engine faster. The fouled plugs, particularly if they are Iridiums, could well be a contributor to your idling problems.

The surging may well be the ATTESSA complaining about worn rear tyres.

[livewire]

Well it definitely did make a difference so I recommend others try the same if the same symptoms ever occur. I may try to get a video tomorrow to show the difference.

As for the plugs, if you read above, we actually only put the new plugs in today and the ones that we took out weren't fouled anyway but I just put the new ones in since I paid for the iridiums.

Never knew the attessa system complained about rear tyres lol. Im pretty sure there is still plenty of tread, it happened when just cruising on a flat, straight road at 100-110km/h at +/- 3000rpm so I doubt there would be any traction loss. Will take it for a drive tomorrow to see if it still does it.

[livewire]

Also. if the attessa system was faulty would it not light up on dash?

[Badgaz]

AFAIK, the ECU ignores the O2 sensor(s) at idle and on a cold engine, so I am perplexed that unplugguing either of the sensors made any difference.

You may well have fouled the plugs by letting the engine simply idle to warm up. Engine runs rich when cold, best to drive it to warm up the engine faster. The fouled plugs, particularly if they are Iridiums, could well be a contributor to your idling problems.

The surging may well be the ATTESSA complaining about worn rear tyres.

the factory narrowband o2 sensors are used for idle and cruise conditions (light load) no factory tune car i've ever seen will foul plugs just from letting it idle to warm up. you are talking about water temp fuel correction....the ecu will input more fuel when the engine is cold.

[livewire]

Thanks for that Badgaz. So If the front O2 sensor unplugged fixed the rough idle there's a good chance the same sensor was causing the surging under low load cruising (hopefully) lol

[Badgaz]

Yep a fair call to make

[livewire]

Ok so just went for a good drive to sit on 100/110km/h for a fair while and low and behold, it drove better and smoother than its ever driven! No hesitation, surging at all and actually feels like it has more power and better acceleration which may have something to do with the filthy fuel filter we replaced lol.

[skylinecouple]

I had the same problem. It does affect the idle and definitely affects low rev cruise quality and mostly acceleration. By acceleration I mean backing off or cruise then move the accelerator and there is a flat spot or hesitation. Accel-enrichment does not help. Disconnected the O2 and drives just like a factory car. I have since changed all cells at light load and cruise to 14:1 AFR and run without a O2 sensor. It is better on fuel consumption at 420-430k to a tank and drives beautifully.