Lately my car will occationally run at a higher RPM than normal. It's as if it is having a hard time getting into another gear some times. Today it was fine, but on a trip last week I was running around 4000 rpms pretty much the whole time on the highway. Additionally, every once in a while I will punch the gas and nothing will happen. Stopping the car and running the gear shift through all the gears and back corrects this.

Sidenote, I have been having issues with CEL - O2 sensors. My mechanic cleaned a bunch of stuff and said it would correct the problem but it didn't. Dont know if this is related to the before mentioned problem. Please help!

 

Welcome to Club Lexus!

It's possible you don't have overdrive anymore, I'm basing that off the fact that you said you were at 4000 rpms on the highway.

What CEL are you getting specifically?

 

Im getting "trac off" and the CEL. The p code if I remember correctly was like p171. When I fill up with gas all the lights will go away and the car will drive normally. But about 50 miles in or so the one or both of the above mentioned lights will come on and I am starting to suspect that when that happens is when the rpms kick up. Just rollled 150K btw. Thanks for the reply.

 

P0171 is kind of a generic "fuel system too lean" trouble code. Lots of different things can cause this including loose induction plenum, bad MAF sensor, low fuel pressure, bad A/F sensor, dirty fuel injectors. You really need more data to narrow down the cause. Do you have a scan tool that you can use to read freeze-frame data and monitor other sensor outputs? I use the Torque-Pro application on my Android smart phone and it works great. (not affiliated with the author, just a very satisfied custormer). From what you've said so far, I would tend to investigate fuel delivery.

Baetke

 

I suspect the codes are just from flooding the motor the real issue maybe you need to clean your transmission filter.

 

For the P0171, I would start with cleaning the MAF sensor.

But, that doesn't explain the high rpm's.

Next time you are on the highway and the rpm's are high, press the overdrive button and see if the rpm's increases even more, if it does not, that means you have no overdrive. Check for any pending codes.

 

I am pretty convinced that my p0171 code is disabling my OD. Here are some suggestions that I have come across. Do any of these seem reasonable or any that are unlikely?

Clean transmission filter, clean MAF sensor, replace coil pack, vacuum leak, knock sensors, clean valve body assembly.

Should I just have my mechanic replace and clean all the issues above or will that be way expensive?

 

Try focusing on the known/indicated problem. Do not add unrelated work to the mix.

It may be worth paying higher labor rates to diagnose the problem, The things you listed can run up the $$$ just in parts (and the parts needed to replace the one you are changing ,,,, knock sensors need gaskets and coolant etc)

Salim

 

+1, do not just throw parts at it.

 

 

I don't think either of those codes will put the car in limp mode. And limp mode wouldn't effect driving from a stop.

I had an occasional issue where car did not go when I pressed gas. I drained the transmission and replaced the screen.
Hasn't happened since.

 

High rpms I'm having same problem running at 4000 rpms while at 75 mph and I also have bad 02 sensors not sure if it has something to do with it my car is also a 99 lexus rx 300

 

You're locked out of overdrive. Fix the issue with the sensors and you will get overdrive back.

 

Just from experience and reading about RX 300 tranny issues on the net, I find that many issues and tranny's in particular are related to a ground fault between the ECU and sensor or solenoid.

On any vehicle, they develop ground faults as they age. Water gets into the ground wire contact points, etc. Almost all of these are crimp only wires. The battery terminals get cleaned at least as often as the battery gets changed. But teh ground points never get touched. Eventually the contact develops "crevice corrosion" which is actually a primitive semi-conductor. So about 0.3v drop across the junction and current limiting. This is one reason why cars start to feel "old". Lights dim, radios get more static, etc.

The answer is to renew the ground side so currents flow easier. there is positive voltage in a circuit to the device, but none on the return side. But still has to flow the same current. So to see is this will help, make up some new ground wires. I use #4 wire from the auto parts house, but whatever you can find is good. Make a lead to go from Battery Neg post/clamp to the engine and then on to the firewall. Preferably the alternator mount. *** these systems including the alternator voltage regulator need to "see" the same ground or they do strange things like overcharge the battery slightly shortening its life.

The new wire should be crimped and soldered to eliminate the possibility of crevice corrosion between the wire and the crimped terminal. And it should go to a clean surface where it's bolted down. A bit of Never-Seize at the bolt points does not hurt. Hood hinge bolts are a good contact point for the chassis. After installation you should see brighter lights, less CEL's and it may cure some tranny issues with teh solenoids not reacting properly

You'all might also want to read this discussion about tranny faults and diagnosis: https://gearsmagazine.com/magazine/c...hift-troubles/