Greetings,
I have an EP2 civic with a custom decat exhaust system that has had the downstream O2 sensor cut off, the car sounds like it runs on 3 Cylinders.

Will the ECU recognise there is no sensor signal and adapt to rely souly on the sensor 1 signal to map fuel or will it cause issues to the ratio and make the vehicle misfire because of the loss of sensor signal?
The reason I ask is I cannot get to the end of my misfire issue no matter what I try, the engine is a D16v1 with engine management controlled ignition timing.

The only code I get is P0141 (Bank 1 O2 sensor 2) which is my downstream sensor (which is no longer existant)

There are no error codes regarding the misfire even though the car misfires horribly like it's down a cylinder.

So my question Is whether deleting that O2 sensor because of the aftermarket decat exhaust will cause the breaking up and whether anybody else has had the same issue with aftermarket or decat exhausts or has had a decat exhaust with O2 sensor delete and had the car run fine.

Thanks in advance.

 

The only thing removing the downstream should trigger is a sensor and catalytic efficiency code. If you have a bluetooth code reader you should be able to see sensor voltages of bank 1 and 2 and the fuel trim for 1. Check those readings and if they're over 1volt or fluctuate too much you might have an upstream sensor problem and running too lean.

 

Fantastic, thanks.
Are there any programs you would recommend to monitor the voltage? I have access to a Laptop and have a Elm327 WiFi Obd2 adapter.

 

Fantastic, thanks.
Are there any programs you would recommend to monitor the voltage? I have access to a Laptop and have a Elm327 WiFi Obd2 adapter.

 

If you have an iPhone I would connect with the Car Scanner app on the App Store. Just checked and that shows fuel trims. If you have Android theres always Torque. If its easier to use the laptop you can find a copy of ScanMaster-ELM that should show the same info.

 

Thanks, I have installed Torque and monitored O2 sensor readings, they seem to spike sporadically on steady throttle, if I upload a screen and microphone recording could you give me a basic overview as to whether I am right in thinking something isn't right here with the sensor reading? The car begins misfiring at 2000rpm then fades, 2k rpm is by far the most noticeable for misfires.

Thanks man👍

 

Yeah go for it. Would be easier with a graph included in the recording. Even better if you can show coolant temp and timing advance. Don't know if thats a thing in torque. Did it show any codes even if theres no CEL? Have you tried pulling coils yet?

 

I'll get a recording for you tomorrow and yeah I pulled each coil plug one by one and it affected the idle ability massively upon each plug removal, idle has never really been a problem it's just 2,000rpm where it splutters and then returns to normal above and before, this is a real strange one to me but to somebody with knowledge the fact it only splutters at 2000 rpm may indicate something specific, anyhow torque is actually very basic and limited from what I have observed and the most detail I can get from it is a O2 sensor graph, no knock detection / misfire logs or anything useful aside from coolant temp and oil temps, nothing else seems to work or is available, I'm looking into finding a decent ob2 cable so can use to plug into a PC to get more detailed diagnostics, so far no codes what so ever apart from the Bank 1 Sensor 2 which is caused because the wire has been cut and the sensor plug deleted.

Thanks again for your support 👍I'll upload some data logging tomorrow

 

Hello mate, I have uploaded a 3 minute sample for you of my engine audio and O2 Sensor Data graph screen recording through Torque Pro, the link will be attached below.👍
You can hear how awful the misfires are specifically around 2000rpm, the O2 sensor data is absolutely all over the place, seems a tad too arratic, would you agree?

https://www.mediafire.com/file/ixybg...2Data.mp4/file

 

Let me know if the link I provided works

 

Looks like your sensor is working just fine to me. Surprised you don't have a catalyst code. So you haven't narrowed down to a specific cylinder? I would pull plugs and check for fouled. I know HDS has missfire diagnostics if you get an openport or HIM. What voltage does it show for sensor 2? You said it seems to smooth out above the 2000 rpm range

 

Plugs are reletively clean, recently replaced, have been gapped correctly and aren't yet fouled, they all look identical so there's even wear between them, my next step is to purchase a cable to run deeper diagnostics on the misfires, I'm starting to think it could be either head gasket (worst case) or fuel strainer, from what I've seen online these cars -(2005) don't have your regular fuel filter they instead have a strainer built into the fuel tank unit, I did use some injector / fuel system cleaner but it didn't make the slightest difference🙄 Voltage for sensor 2 would be the catalytic sensor right? I'll check for the voltage shortly, I would assume it would be dead as the wire was cut

 

Another logical suspicion of mine is the brake booster, if I pump my brake at idle it revs to 1.5k, that would make sense in regards to the misfire because vacuum leaks are at their worst at low rpm but then again it revs fine before 2k its literally only between 2k and 2.5k.. I'm really stumped with all this, I'll grab a cheap booster over the weekend and give fitting it a go anyhow

 

Seems like that would cause even more misfiring at the top end. Doesn't sound like a strainer issue. Would be interesting to see what voltage ECU sees.

 

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Do you have a way for me to test the voltage to the ECU? I'm interested to find this out too.

Spoke to a tech at work today and he seems to think it could be an injector malfunctioning at different pulse rates, which would explain why it only troubles at 2000rpm.
Looking to speak more with him about it tomorrow, added a fuel rail and 4 injectors to my basket on Ebay, only £15 so it is worth an install to eliminate another possible factor 👍