Hi guys,

I have a JDM DC2R. So the car only has 1 O2 sensor.
I have an AEM wideband A/F sensor, DEFI exhaust temp sensor and OEM O2 sensor on my Kamikaze down pipe.
Before I changed my exhaust, A/F ratio would be at around 15-16 at idle and slight throttle cruising on a highway.
I had my exhaust replaced yesterday. After replacing my exhaust, I noticed that the A/F ratio would jump all over the place during idle and cruising. Sometimes it would stick at around 10-11 for a period of time, then it would suddenly jump to 17-18. And when Im cruising and I let off the throttle and press on the throttle again, the car seems to stutter a bit.
Engine light is not on and Im not getting any codes.

I plugged in the Hondata to see what the readings were from the stock ecu. The stock ecu A/F ratio was constant at 10, while on the AEM gauge, its kinda all over the place.

What might be the problem? Damaged O2 sensor?

here are some pics of where the sensors are placed.

1st sensor is the OEM O2 sensor
2nd is the AEM wideband sensor
3rd is the DEFI exhaust temp sensor.

 

Well aem sensors god bad every so often so that could be it but what bothers me is the factory ecu is reading 10? That's crazy rich

 

It shouldnt be the AEM sensor, cuz its new, its only been running for less than a week. And its only hooked up to the gauge, so it wouldnt affect the car running.
Yeah, the factory ecu shouldnt be reading a constant 10.
Thats why im thinking replacing the o2 sensor first.

 

What's also Wierd is that, the ecu reads a constant afr of 10, but the afr on the aem gauge is constantly moving. That's what's causing me to think its the oem o2 sensor getting wrong readings.
On the AEM gauge, it would slowly drop to 10, stay there for a while, then suddenly jump to 17-18, then slowly drops to 10 again. During idle, this cycle would go round and round.

 

UPDATE:

I replaced the OEM O2 sensor and now it runs normal.
On the AEM gauge at idle, it runs a constant 14.5-15. Very stable now.

But when I plug my laptop to see the readings from the ECU, the AFR reading from the stock ecu is around 11-11.5 when its 14.5-15 on the AEM.

Both sensors are new. Any idea on why there is such a big descrepancy?

 

How can you read the value of a stock narrowband sensor?
Are you using some kind of tuning computer like Hondata?
Last I checked, you couldn't really use the narrowband sensor to tune. If you do have a tuneable ECU, why not just connect the AEM to the ECU and make adjustments accordingly?

If you have a stock ECU then I wouldn't worry about it too much. If the AEM is reading properly that's all that matters.

Also, is that an exhaust gas temperature sensor next to your wideband?
If so, isn't that a bit too far from the cylinder?
When we install those, we usually put them about three inches from the cylinder. That way you get a good reading of what's happening inside.

 

Im reading the stock O2 sensor through my Hondata. Its not tuned using the narrow band. Im just looking at the AFR the ecu reads and comparing it to the AFR the AEM wideband reads.

Yes that is an exhaust temp sensor next to the wideband. Any pics of where it should be put? 3 inches from the cylinder would be on the primaries right?

 

Gotcha.
Correct. They're usually installed on the primaries.
Usually when you do EGT sensors you do them for every cylinder. But if you only want to use one, I would put it on the #3 cylinder as it tends to run hotter than the rest.
What does your EGT gauge show during a WOT pull?

 

Ok, Ill consider moving the sensor then.
I havent had a WOT pull yet. The engine was just recently rebuilt and the exhaust temp gauge was also just recently installed. Im still running in the engine.
But cruising on the highway at around 3,500rpm, the temp gets to around 4-500 degC. Is that normal?