I have a all black 1999 Lexus RX300 with about 158,000 kms , this car has been babied from day one with every Lexus service maintenance on file. And it goes a little something like this.....Just last Monday I was cruising downtown, when I approached a stop light, I notice the car started to idle real low almost close to zero and could smell fumes of gas through the vents. I can also feel the engine vibrating through the steering wheel, then the "check engine" icon appeared and started to flash about 5 to 6 times(does this happen on a RX? B/c my LS does not do that.), then it stayed lit. So I pulled over right away to look at the problem, but I allowed it to run for a bit in order to find out what is going on under the hood. As I got out of the car after I popped the hood, I was 1st drawn to the back of the car b/c I can hear the sound of the exhaust(which is factory by the way) like a nice toned performance muffler, but also noticed it shaking. I popped up the hood seeing the engine vibrating along with a smell of rich gas. So I shut it down right away, let it chill out for a bit, pulled the negative battery just to reset the damn deal. Hooked everything up and started the RX to head over to an independent Lexus Mechanic I know. On my way there it was hesitating at times, and idling real low @ stops, and then the check engine icon appeared again by flashing a few times before it stayed lit. Plus I had to keep the windows down as I was close to feeling a little up there b/c of the fumes coming in. When I got to the shop, the mechanic ran a diagnostic check to find out what the problem was. It showed Bank 2 manifold, A/F sensor a.k.a. O2 sensor(can't remember the code exactly) located between the engine and towards the front fans. So I said "order one up!", but he hesitated a bit because other readings he was getting in his computer from what he states are "really odd numbers". He continued to scope around and found out right away what the problem was. Where the A/F sensor is located on the Bank 2 manifold there was a 2 to 3 inch faulty crack on the other side of the manifold parallel to where the A/F sensor is attached . Keep in mind that the manifold is not even rusted at all, more so a manufacturer's defect as the mechanic concluded. Also adding that it could not hold the pressured heat that it cracked open, so the reading that the A/F sensor was getting is extreme oxgen from the outside that it started to pump more fuel into the engine, that is why it started to bugg out on me. Sensor may not be faulty @ all. And the mechanic further advised to call Lexus of Canada to file a compliant and should replace @ nocharge. He has been a certified Lexus mechanic in Canada since its' debut and states this is the 1st he has seen on a RX. Has anybody else experience this type of damage? I also have a 93' LS4 with about 270,000 kms with the original manifold in great shape. So I am assuming it's defective for sure. I will call Lexus of Canada later today and demand to have this replaced at their expense along with a thorough check up with the rest of the engine as it could have inflicted other damage, in hopes that they will do something about this....wish me luck, keep you guys posted. As for the rest of you guys and gals that drive a RX, you may want to check it out and make sure everything is good to go!

 

I don't know how common this problem is, but I do recall reading some other posts about it.
Here are a couple of threads on the subject:

https://www.clublexus.com/forums/rx-1st-gen-1999-2003/74826-cracked-exhaust-manifolds.html

https://www.clublexus.com/forums/sho...d.php?t=149286

 

I don't complain anymore, I just weld the sucker.

 

I called Lexus Canada today and spoke to one of the representatives and mentioned my situation. They were helpful and understanding that they simply said to take it to my local Lexus dealer today(just got back) for storage and that it will most likely be approved by head office to go ahead and replace the cracked manifold and A/F Sensors at their cost even though I have about 158,000 kms'!(no extended warranty by the way) Since we are going into the weekend, the Lexus headoffice will call my local Lexus dealership on Monday for the final approval even the local Lexus dealership stated it should not be a problem.....all it took was a phone call. Not bad @ all!....Well after all, Toyota does have a $30 Billion dollar cash reserve!

 

It's rare, but occasionally exhaust manifold can crack. Just luck of the draw. It could also happen when the manifold experience rapid temperature variation - like water splashed onto the hot manifold. Like Lexmex said, welding it shut will do. If Lexus wants to pay for it, let'em go at it.

Toyota's $30 billion cash reserve may be down a bit after buying GM's interest in Subaru.

 

Let me add that for all that you have been reading about what I do with my car, that weld that my Uncle (who is also my mechanic) put on has held on really strung even going through puddles of water and the heat of 1/4 mile racing.

Weld it.

 

Worst case, welding would have been my last resort, but I figured since that 1-800 number was on the Lexus site, it just did not hurt to ask. Good looking out though boys, and thanks again for the assistant to the matter.

 

This was a common 99 problem. Ain't cheap to fix, especially the sensors, or at least one of them, as I recall there are two.