2000 i30 rough idle on startup code P0140

[peterr22]

My 2000 i30t with 190k on it started idling very roughly (misfiring?) when i first start it in the morning(~80 deg f temps)

I brought it to autozone and they came up with code P0140.

I need to get this problem fixed but need your help before I just start throwing money at it, thanks!

[maxhopper]

Your DTC code relates to a bank 1 rear O2 sensor (second sensor after the exhaust manifold on the fire wall side of the engine). That may or may not be the issue with your idle.

[loystock]

As always, "max" is right on the money. The HO2S2-B1 (Heated Oxygen Sensor 2 - Bank 1) is mounted in front of the Bank 1 Pre-Cat (mounted horizontally just below the engine. Safely jack up the front pax side and you should be able to see this sensor with WHITE harness while the 4-wire connector is mounted close to the radiator. The OEM Bosch is @ $150 plus shipping but the OEM-compatible NGK/NTK 24572 is @ $100. Right now, you can get this sensor from Amazon for @ $78, with free shipping.

http://www.amazon.com/NGK-24572-Oxygen- ... B001PN8VB6

The rough idling after starting is definitely not due to O2 sensor since the ECM is still in open-loop mode. The ECM only uses the O2 sensors (close loop) once the engine has warmed up.

You might as well check the entire air intake - air filter (replace as required, clean the MAF sensor (with zero-residue Contact Cleaner or CRC MAF Sensor Cleaner) and clean Throttle Body (never spray directly, use rag). Also clean the IACV. There are numerous threads on how to do the tasks above, including those in the forum 'sticky.'

[peterr22]

thanks guys, did the things you suggested, we will find out in the morning how it turned out

[loystock]

Keep us posted.

[peterr22]

ok so I cleaned the maf, cleaned the throttle body. and reset the codes. Drove it for a week(1k miles) it still idles rough on cold start up.

Today i brought it back to Advance Auto and the codes I got were
PO430 Catalyst Efficency Below Threshhold
PO38 02 Circuit High Volume Bank 1 Sensor 2
PO140 02 Sensor Circuit No Activity Bank 1 Sensor 2
PO220(maybe 720?) Output Speed Sensor Circuit Malfunction----Any idea what this is?

So today I replaced the 02 Sensor since it keeps coming up, we will see how that helps.

[MTZI30]

Well it sounds like you have a couple of bad 02 sensors. Im pretty sure inifiniti has a tsb that says replace both post catalyst 02 sensors at the same time. Also looks as though your catalyst is no longer working right, pretty common on these cars. However that would hurt your drivebility. Your rough running is probably due to that output speed sensor.

[peterr22]

Ok I read here that the output speed sensor could be caused by a wiring issue(on a 96 Maxima)?
http://en.allexperts.com/q/Nissan-Repai ... nction.htm

Have you had any success on bringing it to the actual infiniti dealership to get a specific diagnostic?

I don't want to go around replacing parts that aren't really the problem, but I do need a smooth running car to do a lot of hwy driving with roughly 600-700lbs in the trunk(maybe thats the problem?).

Thanks