I recently purchased this Vehicle, with little history. Well, it was service at Lexus upto 100k so I have upto there. It has approximately 193k miles. Was having intermittent trouble with acceleration hesitation, in 2-4 gear. There were no codes. I changed the filthy engine air filters first. No change. I drained and replaced 9qts of transmission fluid. (Was not the problem) I then replaced the spark plugs with oem plugs. I also cleaned the maf sensors at the same time. I'm not getting the hesitation anymore, but I have EOBD scanner and was running it after changing plugs. I noticed I was getting intermittent misfires in multiple cylinders. The misfires were present before changing the plugs too.
the hesitation seems to be gone after doing the plugs , but the Cel came on with code p2238. It came on first after disconnecting negative battery cable and replacing it while doing transmission fluid change, so I thought it was an error since it seemed to disappear after turning the car on and back off. The cel came back on sometime later within 100 miles. I'm hoping someone can read this data to see if it tells the fact the bank 1 sensor 1 actually is not functioning correctly, or if you notice something else amiss. If you have any other helpful info I welcome it too.

I gathered this data before reseting the code, since i needed the cruise control and the pre collision system will not allow it while cel is activated.
if more data is needed i can gather it if you let me know what is needed. The misfires are random, not constant and on almost all cylinders. I can go thru the data to find out exactly where and how much of it helps. The coils appear perfect and I've read they're pretty bullet proof, but I was thinking about testing them if it comes to that. I just don't want to keep chasing this beyond what was done, which is the necessary maintenance that was already needed.
I've also attached the condition of the plugs that I replaced, possibly the original plugs from the looks of them. Obviously the engine has been running lean for some time. Top Pic of plugs is passenger side starting with the order the plugs came out, last one being from the firewall. I know the valve covers are leaking too. That's next on my to- do list.
second pic of of plugs is driver side in same order.
the bank 1 sensor 1 is in a tough spot, so I want to be certain or close to it before changing it. Besides the cel, the car is driving so much better after changing the plugs. If it wasn't for the scanner telling me there's misfires present, i wouldn't suspect anything at this point because the cars driving just about perfect. I'm hoping the misfires aren't due to something else, and in turn triggering the 02 sensor code. They're probably two separate issues. I'm hoping I can tackle this problem and get rid of them once and for all though.
I would take it to my mechanic, but his shop burnt down and I cannot find him nor do i trust shops or the dealer at that to fix this. I figure everything I've done was necessary maintenance anyhow and the way the car drives I'm hoping it to last too maybe 300k or so miles.
again, any help is really appreciated. I've read so many articles on hesitation problems and I'm so happy I got that with just the plugs. Oh, I also ran a bottle of techron fuel injecter cleaner too.



Any help is greatly appreciated. thank you all.

 

You may have a valve guide issue based on that plug on the right......

 

I replaced the spark plug seals. They were cracked especially on the passenger side. Could it be that oil was leaking from there? The coil pack had some oil on the tube also.

 

 

At this point I'd do a compression check on the engine. I'd want to know if the engine is basically "healthy" with good compression before I threw more parts at it first. If all compression readings are in range.
Standard compression pressure: 1400 kPa (14.2 kgf/cm2, 203 psi) or more
Minimum pressure: 980 kPa (9.9 kgf/cm2, 142 psi)

And fingers crossed, your compression is good, then I'd proceed to check everything else involved, since any number of things can cause an engine to perform as if it has power loss somewhere.Could be anything from a couple dead coil packs to a restricted exhaust system but first things first, I'd want to know that this engine is basically sound before putting more effort into fixing it.

 

So OP making any progress on your Lexus?

 

thanks for following up, since the spark plug replacement I've only done the bank 1 sensor 1 o2 sensor. So far no more misfires or cel, nothing. I still need to do the valve covers, pcv and compression test. I just haven't had the time. I care for my infirm wife 24 hrs a day. She deals with a lot of health problems; seizures, Paraplegia etc for the past 8 yrs. So it's difficult to find the time along with the right head space for me to tackle it, but I'll get around to it. I'm pretty amazed at how great this car drives after doing the work I've done to it. I still need to know if there's a leaking valve guide are worn out rings though. So far so good and my work paid off. I actually just ordered the STAR BRITE Star Tron Ring Clean Plus today, not sure if you recommended it or somebody else did but it seems to be good stuff to try out. Other than that I have the pcv valve and valve cover and other related gaskets for when I get the time to do the work. I really wish someone here lived nearby and was willing to help me out with the work. Anyhow, thanks again for checking up on me Marc. I appreciate your support 🙂

 

That's a whole lot of demands for your time alright, glad you seem to have got it running well apparently! If it idles smoothly there might be nothing wrong with the PCV valve. If I had all the PCV valves I ever changed that didn't need it I could fill a bucket probably.
If and when you do the compression check, that plus the oil consumption if any, will tell you if you have a problem that needs more attention paid to it. If it idles and runs smooth, oil consumption is not excessive (I've never owned a Japanese car that used oil) and your engine power seems normal you are probably in good shape for a long time I'm thinking.