Margate330

I would say hope on that sensor vs guaranteed, fingers crossed. Lol

What makes this diagnosis astronomically complicated that even the mechanics don't want to touch it is because you have a couple or more issues going on.

Your exhaust leak that you fixed was necessary before beginning anything, like posted above.

It looks like the previous owner did a lot of "deferred maintenance" and let stuff go until the point it was overwhelming. Lol

A couple of things to also try just for quick troubleshooting if you like.

1) it's tight but it can be done because I did it on my RX330, I'd pull the 1st and last coils on the bank 1 and swap with bank 2. Cold engine of course. And feel in there and make sure the coil connectors and fuel injector connectors and pushed on tight. Sounds crazy but from experience on my car, my weak coils(weak spark)were adding +10-15% per coil as they failed to my fuel trims while only rarely throwing a misfire code. Why? Unburnt fuel is seen as a lean condition because of the unburnt oxygen measured by thr O2 sensor. Haha. Swapping coils will quickly rule out weak spark adding to lean condition misfire because the problem will move to bank 2 when coils are moved.

2) I was waiting until you had more info but your MAF should be close to 3.0g/cm3 at idle. This affects both banks equally so it does not explain the drastic difference of fuel trims between banks. Only adding to the confusion. Lol

brandonfpv

OMG. are you serious? this makes a lot of sense. thus, it adds more fuel, which makes the "lean" condition even worse, exponentially adding fuel in order to meet the o2 sensors desired voltage. I am going to swap right now. I have already switched coil #5 with #2 and just left it after receiving 1 3 5 misfire again, but I will try doing 1 and 6 as well. also I cannot take that o2 sensor off for the life of me. just going to try the coils before going back to mechanic but I found a new place with a cheaper labor rate.

Margate330

Luckily on my car the coils each died a slow death one at a time and I tried to be right on it.

It drove me absolutely crazy.

I'd get a once in a while random misfire code and a lean code and then it would be fine again.

But, my fuel trims were always +12-14% on just one bank(a little on the high side) and perfect on the other, my fuel economy was terrible at 10 mpg.

Average fuel trim increase I saw was about +10-15% per failing and weak coil.

Doing the coil swapping at one coil at a time my fuel trims moved to the other bank

Talk about feeling dumb, before I became member I didn't know about fake cloned parts being sold on ebay.

Thought I was saving money getting denso "oem" coils for $20 each.

They all died one after another within 2 years and the amout of frustraition was unbelievable. Haha

Anyway, just a fun story I went thru I thought I'd share with ya'll.


Ps- there are other things that can cause a lean condition on just one bank.

brandonfpv

well, I swapped all 6 coils and while doing so I stumbled upon this...

coil 1

coil 3

coil 1 was soaked, coil 3 had a line of oil around it. earlier in this thread I was asking about a spark plug seal, this is what salim (I think) was talking about. I guess this isn't a big concern though, yet, as im not losing oil and It might be from when the valve cover was loose. not sure. also, I know they aren't stock as the previous owner said he had swapped them.

swapping them did nothing though, unfortunately. thank you for the information though @Margate330

Margate330

Oh man, I was really hoping that could be some of your lean condition and it's free to test.

Ok, not weak coils and connections are on tight.

Moving on, lean condition like Maxsteel's video above is often a vacuum leak but this will be harder to rule out

Does anyone know a safe and easy way to do a quick vacuum leak for bank 1 test on our cars to rule that out?

Anyone have more ideas for bank 1 lean please post. I will only keep posting if others do too. Lol

brandonfpv

going to try to swap o2 sensor still. I find it weird how on closed loop is when the fuel trims are out of wack. I mean from what I am learning this is normal, but I hope the sensor is causing this. the cable looks fairly new, so perhaps someone replaced it with a cheap sensor. guess we will see

brandonfpv

Well, after swapping the o2 sensor with a fresh denso, (from a brand I don’t recognize) the car runs pretty well if I say so myself. Please don’t tell me I jinxed it. As of now, it will pass inspection. Unfortunately the place closed so I will have to wait until Monday , but 25 miles no CEL and fuel trims actually look normal. Knock on wood. I’m very superstitious.

salimshah

Good to know, but keep in mind that you will only pass inspection if all the channels are ready. That means all that needs to be monitored has had enough cycles to determine things are working as designed. It may take you 3-4 days, with driving patches of on in excess of 45 MPH and predetermined number of start and off cycles.

Salim

If you need cleared the codes by disconnecting the battery, you may be ready.

brandonfpv

Actually salim, where I’m from (New York) you are able to get away with 2 out of 4 monitors blinking on vehicles that are over 20+ years old.

But either way, I’ve been driving for about 40 miles now and still nothing. I pray that this remains. Gas mileage is amazing it is a fun and enjoyable drive , I see why you guys love this thing so much (I knew since day 1 I fell in love haha)

Wish me continued luck…

Margate330

I am happy for your success @brandonfpv .

Your car is a good case study of what happens when someone like the person you bought your car from delays maintenance too long. Lol

Now that you got the car running ok, you can over time and at your convenience touch up things as needed.

I was really hoping that O2 sensor would help, because if not I was fearing fuel injectors, lower intake vacuum leak, or worse.

brandonfpv

The journey isn’t over.. its never over, there’s always room for improvement..

however, this new issue is sort of pressing, as I just got a check engine light (p0171 and Evap circuit? P044x) today after 3 days with clean and serene driving. What a tease! I check the spark plug and it’s got oil on it again. I tried to remove the other spark plug but I couldn’t. It’s so tight back there. Any suggestions? I’m almost positive that bank 1 is just covered with oil and the people who fixed the oil leak didn’t bother to empty the spark plug wells. I plan on doing this by putting rags in and cranking the engine . That is if I can even get the spark plugs out lol..

brandonfpv

Oh and here’s my fuel trims now.. much better but bank 1 is rich/sensing lean. My guess is there is oil in the other spark plug wells. Gonna have to attempt to take a look.

salimshah

Oil in spark plug access hole comes from leaking Orings which are in the tube of the valve cover. Purchase Felpro if you think OEM is too costly. Usually the tube Orings are part of the kit.

If you are removing the plugs, think about replacing them and ONLY purchase OEM pre-gapped plugs. Take note of the make of ignition coils. since they are working, I would not replace them just yet.

I think now you are on the path of spending some dollars which the previous owner chose not to and the risk you took in purchasing hopefully a cheap lexus.

Salim

FYI my well maintained first gen RX was declared totaled 4 years and although I respond to issues, but my ride only needed oil changes, filter changes, brake pads, tires many times. No transmission or engine issues.

maxSteel

Haven't heard Sade in a while

Those trim numbers are acceptable. Diagnostic says if the total STFT and LTFT is within ± 35 % at operating temp the system is functioning normally.
Unless there is a problem to solve (like the exhaust is still flaming) in your place I would declare victory and close the hood until the car says otherwise

It's not weird how "on closed loop the trims are out of wack", it needs the sensor feedback loop to adjust trim.

I'm not aware of a reduced emissions testing requirement in NY for 20+ year old vehicles. There is for 24+ year old vehicles: https://dmv.ny.gov/brochure/new-york...ection-program

brandonfpv

Haha this car comes with lots of hidden gems, especially in the 7-CD mixer for my case.

i drive it normally, for 3 days I get at a time of pure enjoyment , then a check engine light. P0171. I passed inspection thank god, but I’m just concerned that oil on the spark plugs is making for bad combustion? Also, I hear clicking sound with each revolution of the engine. Sounds like a Chevy. When I changed the same spark plug, white smoke and then it clears up . I hope I don’t need o ring seals , because it sounds complicated and costly, but If the issue persists though that will be my first guess.

Yes, it was 24+ years, I just thought for some reason it was 20 or 25.

I thank you guys again for the help thus far, and your continued support in these early times for me. I’m now at 300208 miles strong. I am going to try to share the knowledge you have helped me gain with anyone I can so they hopefully can resolve a similar case like this in half as much time as I did. Still, lots of work to be done to this ol’ car.. I’ll keep you updated as I hope you guys do the same.

Just broken in.