ps342

Hi. My automatic 1999 rx300 (139000 mi) has some problems. It accelerates very slowly, and does not shift gears at first. After 5 minutes, it starts shifting better, but can only be driven to a top speed of 35 mph, really pushing it. It does not shift to the highest gears. Occasionally while accelerating out of my parking space I hear a single clang from underneath.

The exhaust smells unusual and bad. It is almost rotten (sulfur) but I am not sure.

A mechanic I go to regularly always notes that both O2 sensors are out, and when I brought it in, he said that the problem was JUST the sensors and was charging me $750 to replace them.

I took it home and have been making small and short trips with it, driving very slowly. Sometimes when I start driving it on my street, it doesn't go above 10 mph until I hit a certain uphill bump, where it starts shifting and accelerates as described above.

Some other notes:

For a while the engine had been misfiring so all new spark plugs and 3 new engine coils were installed.

The O2 sensor engine codes have been coming for 2 years, even though this problem appeared overnight. This problem appeared right after I had to jump start the car after letting it sit for 2 days. I just had a new battery installed, and the alternator is good.

I understand that technically there are 1 O2 sensor and 1 A/F sensor, not 2 O2 sensors.


What could be causing this problem, is it worth changing the o2 sensors, and is it even worth attempting to repair the car if I am planning on trading it in at a dealer and want to minimize my costs?

Thank you.

EDIT: After I jump started the car and this problem started, I was driving around when I pushed the car (pressed the accelerator nearly all the way) up a steep hill. After that it stopped accelerating and even after resting the car for 10 minutes was not accelerating. I had to have it towed to the shop. They said it was the O2 sensors. A day later I came for the car w/o doing any repairs and was able to drive it home, in the condition described at the top.

maxSteel

You really need a code reader.

This post has the locations of the 2 A/F and 1 oxygen sensor:
https://www.clublexus.com/forums/rx-...ml#post4871251

The Denso A/F sensors are about $100 each.
The Denso oxygen sensor is about $50.

If by "doesn't shift gears at first" you mean "up shifting is delayed when engine is cold" it is working as designed.

If the CEL is on and it has gone into 'limp mode' it will run rough and will not go into overdrive.

ps342

Thank you. I got a code reader. Codes are:

P0171 System too lean
P1135 A/F sensor B1S1
P1155 A/F sensor B2S1
P1354 VVT malfunction bank 2, Oil control valve problem (https://www.clublexus.com/forums/rx-...304-p0306.html)

It was driving really rough. After clearing codes it's accelerating better, and driving smoother than before, but still very rough. Engine light has not come back yet. Engine temp is good. Oil level is good but oil is blackish/dark on paper towel.

Exhaust is black and smells strongly like gasoline and burning. There are several mechanical noises coming from the bottom back of the car (these come and go, are very mild). I will have the sensors repaired. Do you have any other advice? Thanks!

EDIT: This seems like it could be the problem too https://www.clublexus.com/forums/rx-...ement-diy.html

fastnoypi

you appear to need 2 upstream a/f sensors . Either Toyota A/F sensor is 89467-48011, Denso makes the sensor but uses a different part number for aftermarket: 2349009

And an front OCV sensor

OCV Front (left)(Toyota) 15340-0A010
OCV (Dorman) 917-211


your exhaust is really strong because your o2 sensors cannot tell the ecu how much or little fuel to inject.

ps342

Thanks, I will try and replace those.

The oil on this car has not been changed regularly, last time it went 7000 mi w/o a change. Is it possible that oil is gunking up the a/f sensors and OCV? If so, would I be able to see it? am curious after I read someone saying this. would this be the sludge problem that people sometimes refer to?

fastnoypi

dirty oil will eventually gunk your OCV sensors.
A clogged PCV or rear valve cover breather will recirculate oil mist into your air mixture and damage your a/f sensors after combustion. If they are covered with very black soot and no misfire codes, it is an indication of oil in the combustion

There are 2 revisions of the rear valve cover in the 1st gen RXs. Using an upgraded valve cover from the RX330 model years has been a popular fix for disappearing oil and perceived constant PCV issues.
If you are mechanically capable, your current rear valve cover can also removed and refurbished by cleaning the sludge in the breathers chemically.

IMO, you can most likely get your car operational under 300 if you do the labor.

Roop10

Mine is in limp mode, will not go above 3rd gear, codes from Autozone yesterday says P0125, P1135 & P1130, I just changed the Fuel Vapor Canister (Charcoal Canister under the rear of the RX300) and the hard hesitation stopped but it still has a slight issue w/lacking horsepower. Is it the the A/F sensor on bank 1 sensor 1? Which would be the one on the firewall side of the engine, correct?

cjj2533

That is correct. I just replaced mine last week.