Misfires are reported by CEL code along with flashing CEL.

Salim

 

Hey long time no post, so I was looking at my car earlier and that engine code is still there. Instead of the popping up once every 2 weeks ish I said before, now it appears like 5 minutes after last clear. The gas smell is completely gone and I haven't smelt it since the last post here. Also I can not feel any misfires at all unless the air conditioning is off, the car is parked, and I don't have any music playing, and it only happens like once every 5 minutes or so. Its that unnoticeable.

I still haven't replaced the firewall side spark plugs because of needing to tear out practically half the engine to access them, but I did replace the front 3.

With all that information, I am still confused on what this could be. The only things I could think of is I replaced my broken injector and fuel rail at the same time, both from a 2003 RX300 at a junkyard. I don't know how many miles it had or what the problem was but everything looked fine in the engine bay and the fuel rail fixed the old problem. Also the replaced injector as well as all the other ones are not leaking at all, I have checked multiple times at cold, warm, and hot.

I checked the hoses for incorrect placement and made sure they are connected properly and fully multiple times but did not check for cracks in them with soapy water yet (don't know if that would be the issue cause I would think more air would cause a Lean code.)

Any thoughts? (I am using an old scanner because a friend is using my bluedriver for a week or 2 to fix their truck.)






Also what is the difference between Engine codes and OBDII/EOBD codes? I cleared the engine codes and the light turned off but what does the other one do?

 

Just a minor correction ... the rear plugs can be removed without removing anything above it. You just need to have the proper extensions and be ready to interchange them with the plug socket in the hole. I have personally done that 2 times.

Salim

 

really? I figured it would be easier to just tear out the throttle body and air plenum and that would be easier than trying to reach behind it.

 

If I am not mistaken, one has to remove the wipers, wiper motor, cowl, air intake, throttle body plenum. Every gasket on the intake side needs to be replaced. If some one needs to remove the back valve cover, then do all of the above. If only the plugs have to be removed, 3/8 ratchet, plug socket and two extensions is all all that is needed.

Salim

 

My dad and I just work under the wiper cowl and leave it on, also we don't replace the gaskets every time but we probably should, but the air plenum to valve body gasket or whatever that is called was replaced last time we did that. But I bet if I take off the wiper cowl, then I would have more room to access the spark plugs from above. The reason I say its easier to do all that is because I am 6'2 and above average sized hands for my height, so they don't fit in cramped places very well.

 

Alright got my good scanner back, so I'm about 90% sure I found the issue but i'm not sure so I wanna double check here before I buy anything.

So this picture is from me driving for 30 minutes towards class and I was messing with what was showing at every stop light so the graphs aren't equal lengths.

The thing is though, I don't believe Bank 1 Sensor 2 is supposed to do that.
Bank 2 Sensor 1 was replaced with a Denso sensor at $130 and the Bank 1 Sensor 1, I have not replaced since I bought the car 40k miles ago.
But Bank 1 Sensor 2, was replaced by a $20 aftermarket eBay sensor.

I didn't know at the time but I think the downstream sensor isn't supposed to do that. Also I accidentally lied on my last post, the code appears like once every 20-30 miles driven and randomly (sometimes when parking, sometimes on the highway).

I'm about to replace that sensor but I want confirmation that is an issue and downstream sensors voltage graphs aren't supposed to look like that.

 

One can never be sure that it is the sensor or some other cause leading the sensor to produce the output.

I would suggest measure the ohm or swap with the other bank [presumed good]. At times the effort to carry the swap [time/difficulty/potential of damage etc] is not worth it and replacing the sensor is the most convenient option. The only caveat is cheap(er) part may not be correct [just because the part is OEM, is not a guarantee that the part is genuine].

Salim

 

I can't swap it anyway because the downstream O2 sensor is a different part from the upstream ones.

Upstream Denso - presumed good O2 sensor / A/F Ratio sensor / whatever its called.

Aftermarket eBay O2 sensor.
If I pull the drivers seat and unplug the sensor, do I need to check the ohms of it with the car running? What is a normal range for something like that?

 

I was referring to swapping bank1 with bank2. Because of mounting differences some can not be swapped like OCV

Then there are sensors that present before the split and after the merge and they are unique.

Salim

 

Oh I see what you meant. Yea those 2 upstream ones are matching pretty well on the voltage graphs on the scanner so I think they are both fine. There is only one downstream sensor (the one with the weird graph) so I can only swap it with the old one that I had.

I don't know if it should have the graph looking like that because it's massively different from the other 2, but at the same time google seems to say yes?

That doesn't specify downstream sensors though or if it should be jumping between 0.05 and 0.9 with no in-between.

What is really confusing is this graph is completely different from both of the graphs on the first post in this thread with a before and after graph of the replaced downstream sensor.

Edit: I know throwing parts at a car is discouraged but a DENSO downstream o2 sensor from rock auto is only $51 so I might just buy that straight up. Unless someone who has a functioning rx300 and a graphing obd2 scanner is willing to check their downstream and confirm or deny the graph should look like that 🙏

 

Now we are on the same wavelength, my suggestion was to swap from bank1 to bank2 one sensor at a time and see if the problem moves. If it does not then a new sensor will not make any difference. I know it is twice the work but this is a technique to debug.

Salim

 

I think we are still confusing each other. I was saying that both of the upstream O2 sensors on either bank are fine right now and look to be in normal range according to the graph I sent earlier, and that the downstream O2 sensor that is after the exhausts merge and is a different part is the one with the weird graph.

Are you saying swapping the 2 upstream ones on either bank will possible change how the downstream one is looking or am I misinterpreting this? I'm a little confused on what you mean if that is what you meant for the downstream having a weird graph.

Middle one is the graph of the downstream O2 sensor after the exhaust of bank 1 and 2 merge. The main question I had is are the downstream O2 sensor graphs supposed to look like that or match the upstream graphs? If not, could that cause a bank 1 too rich code?
Bank 2 Sensor 1 (top graph) is the DENSO O2 sensor replacement by the radiator in the picture I sent earlier.
Bank 1 Sensor 1 (bottom graph) has not been replace by my dad or me to my knowledge since obtaining the car 43k miles ago, but it matches the new DENSO graph so I assume its working good.

Sorry if I sound mean in this post, I'm not sure if you did mean for that to be the solution for what I was saying and don't know how to word that better.

 

I am by no means expert in interpreting sensor output.

My suggestion is/was, if there is an identical sensors in the other bank, instead of purchasing a new one, swap them. <= This only helps if one bank is working right and the problem is in the other bank. This suggestion can potentially save you buying a sensor.

Salim

 

Have a look at post #4
https://www.clublexus.com/forums/rx-...-readings.html