P0421 & vents stuck in defrost after messing with throttle body

[joneill]

Hey all! After replacing my OPDA and cleaning fuel injectors / replacing o-rings, the vent selector quit working and a little while later it threw a P0421. I had removed the throttle body to get the fuel rail off, and I noticed the gasket was shot. I ordered a new one and replaced it, and I can select more vent positions (not all), but I'm still getting a P0421.

I bought a smoke test kit and the only leak I could find was at the TB through the shaft. Do you feel the P0421 is related and I'm on the right track? Or am I chasing two different things? Seems to make sense since I was messing with the TB, so that is at least the first place to start.

Thanks!

 

[Chris]

Hey all! After replacing my OPDA and cleaning fuel injectors / replacing o-rings, the vent selector quit working and a little while later it threw a P0421. I had removed the throttle body to get the fuel rail off, and I noticed the gasket was shot. I ordered a new one and replaced it, and I can select more vent positions (not all), but I'm still getting a P0421.

I bought a smoke test kit and the only leak I could find was at the TB through the shaft. Do you feel the P0421 is related and I'm on the right track? Or am I chasing two different things? Seems to make sense since I was messing with the TB, so that is at least the first place to start.

Thanks!

Vacuum leaks can sometimes throw off fuel air ratios and affect engine performance, potentially causing issues with emissions triggering codes.

Being as though none of this happened until you did that work on your TJ, I have to assume that you knocked something loose. The question is what?

I think you're on the right track only because it all happened at the same time. It's possible that it's two separate things, but that seems unlikely. I'd start with the TB first, but did you check vacuum lines under the dash? It's possible you could have pulled a little too tight on one of them under the hood when working under there and it tugged at one of them under the dash causing it to crack.

 

[Rancho LJ]

Also check the HVAC vacuum lines on the engine side that enter the firewall above the AC / heater lines.

 

[joneill]

Thanks all! I didn't pull the dash yet, but I can have a look. I'll start with the TB and keep plugging along.

The HVAC vacuum lines looked OK upon first inspection, but I'll admit I'm still a novice and just learning. I'll have another look.

Appreciate the help!

 

[macleanflood]

P0421 is O2 sensor bank 1.

Have you checked the Cam sync on the new OPDA?

You might be so far out you're causing underlying issues...or not.

Monitoring live ODB data can help. Fuel trims, timing and O2 sensor voltages.

-Mac

 

[joneill]

Have you checked the Cam sync on the new OPDA?

I followed the video in how-to thread here:
https://wranglertjforum.com/threads/how-to-change-your-opda.79/

I was pretty careful lining up the holes on the original and using the pin with the new unit to double check but I did not know to check the cam sync, but I'll read up on that as well.

 

[Link]

Check the vacuum port below the throttle body. That’s where the HVAC system gets the vacuum to work the doors. It’s common for it to get knocked off.

It’s happened to me.

 

[JKP]

Check all the vacuum lines on the intake. You may have knocked some off, and they are known to crack at the elbows.

 

[joneill]

Wanted to follow up. I ended up replacing the throttle body which improved the vacuum leak - I have all vent positions working now except for the two center vents. Smoke tested again and I could not find anything under the hood. I'll pull the dash to track down the center vent issue.

I did have a high idle after swapping the sensors over to the new throttle body. I had tried to clean the IAC valve, which I think made it worse lol. I replaced it and the idle is back to normal. So I think I have cleaned up all the stuff I screwed up after cleaning the fuel injectors and swapping the OPDA. Learned my lesson on how sensitive the throttle body is.

I had the battery disconnected for a day, and after completing a full cycle over the past few days all the O2 sensors are back online without any codes. Passed inspection today, so now I can safely wrench and mess things up for another year. Learned a lot with this one. I have myself convinced it's running much smoother after all my work . Appreciate all the advice.

 

[joneill]

The code came back. I replaced bank 1 sensor 1 (NTK 23018) and reset the codes. It seems to drive fine with no engine power issues, so I'm starting with this sensor and we'll see where that takes me. Let me know if you think I should replace sensor 2 as well. Really appreciate the resources available here like this.

 

[macleanflood]

What's live ODB data showing for voltages?

-Mac

 

[joneill]

I'm not sure how "clean" these should look. Bank 2-2 looks weird?