Hello HT. I have a B18C1 in my 99 EK hatch. I've had the swap since November 2013 and I just installed an O2 sensor yesterday. My car is cat less so I bought an AEM NO - WELD BUNG to install the sensor. I drilled the hole 1" which is 1/8 of an inch bigger than what was recommend. After it was all installed, I pulled out ecu fuse (back up/radio) for 2 minutes to reset it.

I drove on the freeway today and I noticed my car bog Down a little while cruising in 5th gear. I had the gas pedal slightly pressed the whole time and it felt as if the gas pedal was being let off and then pressed again. This happened the whole time while driving, and it usually happens while maintaining the same speed.

Now, can this be happening because the ecu was reset and the O2 is new to the car?

 

Which o2 sensor did you buy?

 

Maybe exhaust leak since you drilled the hole too big. Why are you only now installing an O2 sensor and why wasn't there one prior? Is this a stock ECU?

 

I was thinking about the exhaust leak too. I'll put a rag on the exhaust end and listen for any leaks. I'll make sure I'm in a closed garage too. Just kidding. My swap didn't come with an O2 sensor. The stock exhaust didn't reach the header so I had to get some extra piping welded on (which is why I got the AEM bung). Yes, it's a stock P72 ECU.

Edit: I didn't think it was a big deal to use the car without the sensor. The CEL was on because of it but I didn't mind. I noticed that my car gets 24 mpg at most and I was told I can get better fuel trims by installing the sensor.

 

Which o2 sensor did you replace and what version p72?

 

It was missing the primary oxygen sensor. I'll look at my ecu and post the entire code. All I know is that it's an obd1 P72 ecu

 

bump

 

Don't bump the thread until you post the information you said you were going to.

 

I was going to post up the entire code when I noticed that I didn't specify whether my motor was OBD1 or OBD2. I think that's what Tony was asking me. OBD1 only looks for the primary oxygen sensor, and OBD2 looks for primary and secondary O2 sensors. I told Tony it was OBD1.

 

Code. Post. It.

 

37820-P72-A01
813-126114
Hope this helps

 

I just finished putting gas and my car is acting more strange. I can't stay in 1st gear too long anymore. After a few seconds, it's like the car stops accelerating then accelerated again and that wasn't fun in 1st gear. When I parked, the rpms dropped down to 300-400 rpm. After a short moment, the rpms came back to 900.

Could I have bought the wrong O2 sensor? I ordered one for a 94 GSR, but my engine harness is off some civic. Could that be an issue? My CEL hasn't popped up so I'm guessing the ecu reads the O2 sensor just fine

 

So lemme understand this. It ran fine without an O2 or catalytic converter on a stock ECU and now that you've added one now it bogs? Are you SURE the ECU is stock? Is it an OBD1 or OBD2 ECU? No other mods? And might I ask, if you're adding an O2 why not a cat? What kind/brand O2 sensor did you install?

 

That's right. Adding the sensor made my car drive strange. The swap came off a stock integra so I doubt the ecu is tuned/chipped. If I bought a cat, I would have to go to an exhaust shop so they can remove the old piping and that would be more $$ on top of buying a new cat. I'm not sure what brand. It was just some eBay O2 sensor. I've been told on here that eBay O2 sensors work just fine.

 

And you're also saying you never threw a CEL on a STOCK ECU for these missing components? Here's your fix. Remove the O2 sensor. Unless you have to pass emissions or something.

 

I did have a CEL. I believe it was code #41 when I scanned it, which was the primary oxygen Sensor. That code still hasn't popped up since I installed the O2. I'll unplug the O2 from the harness and leave it attached to the exhaust and see if that does anything (or else I'll have a 1" hole in my exhaust).

 

I just don't understand why you installed a sensor when you weren't having any issues beforehand.

 

To clear up the CEL and to improve fuel trims. Can an exhaust leak be causing this?

 

If the engine runs well with the O2 sensor unplugged, then the O2 sensor is bad or a mismatch for your engine/ECU.