edison2001

I have an RX300 and recently the Check engine light turned on after I changed the oil and filter (dont know if this caused my problem).Sometimes when the accelerator is pressed the car staggers (hesitates) a couple of times then runs normally. This doesn't happen all the time but sometimes. Previous to the oil change my wife told me she was having some problems starting it in the morning. I live in New Hampshire where it is cold don't know if that could be the cause. I was told that it could be the following.

- sparkplugs
- fuel filter (in tank)
- mass air flow sensor
- fuel pump

anybody have suggestions

Fern

Personally, I think the oil change is just a co-incidence especially if your wife was having problems starting it prior...

Just out of curiousity what kind of air filter do you have? Wouldn't by chance be a K&N, would it?

If so, this may be your problem in that it is effecting the MAF sensor.

Suggest you take it to dealer to get the check engine code read out.

Cheers,

Fern

BurnishedGoldRX

If you can take it to AutoZone or somewhere that can pull the error codes, we could give a little better suggestion on what might be wrong.

Lexmexico

- sparkplugs- doubtful as then it would be happening even when the car is not switching gears or accelerating

- fuel filter (in tank)- use some Techron

- mass air flow sensor- Take the the MAF just behind where the air box is. See if the thin piece of wire is covered in black. On one side you should be able to see red. Carefully clean this with brake dust cleaner or carburator cleaner as others have mentioned (I have found no difference). It should be red when done. Then take out the EFI fuse in the fuse box, I believe it is yellow, but is definitely fuse no. #13. Do this with the engine off and the key out of the ignition. Hold the fuse out for about 30 seconds and then reinsert. This will blank the transmission memory and erase the check engine light. Car drives really nice afterward.

- fuel pump- use some Techron

jeremyp111

Get the code read by a shop or at Autozone as said above. Most likely culprit for this is the MAF sensor. Very cheap to fix and very easy too (mine was replaced under warranty).

Good luck,

Jeremy

jeremyp111

diagram of MAF location

Danscorp

Fern:

You said that If I was using a "K&N" filter, it will affect the MAF sensor. Does it affect in a very bad way that I shouldn't use the "K&N" filter at all or should I just clean the MAF sensor like LexMexico stated.

Thanks.
Dan

Fern

The term "effect it in a bad way" is relative.. It does not damage the car if thats what you suggest. Since the K&N is coated in oil, this makes for oil film to be collected on the hot wire of the MAF sensor and as such some people have complained of check engine codes or speratic idle or poor startup.

All said,

these problems can be easily resolved by removing the MAF sensor and cleaning it with the above mentioned products. Personally I have heard that carb cleaner works great. You might want to pull fuse #13 as mentioned by Lexmexico to reset the check engine code.

THANKS TO JEREMYP111 WHO POSTED THE MAF SENSOR DIAGRAM.

Cheers,

Fern

Lexmexico

The K&N filter will not harm the car per se. In fact, when it occurred in my car, it was more a case of an extremely hot day. We have a lot less oxygen in the air at 7,700 feet, so I was not surprised nor was Lexus when they first heard of my issue. Apparently, this has been happening Bolivia (where they also sell Lexus) at 13,000 feet and people also use the K&N to get better power, gas mileage.

My solution was not only cleaning the MAF, but also carefully rinsing off all of the K&N oil and then reoiling just the side facing the air flow. I just took a look at my MAF the other day, 6 months after the problem, and it carefully scratched off the little crud that existed.

All that happens when the MAF gets coated with that crud, and check engine light ensues, is the system goes into a default temperature mode. You won't really get to accelerate or do anything fun, but the car will run until you can fix the issue.

Danscorp

Thank you Fern and Lexmexico! I just clean my MAF sensor today and reset the check engine light. Hopefully that light won't come on again since it all started a couple weeks ago when I installed a K&N air filter.

I really appreciate all of your feedback, I understand my RX300 a lot better now.

edison2001

Just got the error codes. They are as follows:
P0125- closed Loop Fuel Control Insuficient Coolant temperature.
P1133 and P1135: manufacturer specific DTC. See Service manual.
What do these codes mean? I cleaned the MAF sensor before reading these codes. Car smells like gas. Does not stagger as much since I changed spark plugs. Need some recomendations and insight to what these error codes mean.

Fern

What position is the temperature gauge at when you consider car to be at optimum operating temperater?

I wonder if the thermostat is stuck open?

I would call Lexus service and enquire of the codes you found.

Wonder if the symptums are related to vehicle thinking it is running cold. If this is the case you should be noticing abnormal fuel consumption and you could be damaging your cat...

Cheers,

Fern

Fern

Have you noticed car loosing coolant recently?
How is the collant level?

Here is a more descriptive explanation of the P1133 & P1135 codes:

P1133
Air/Fuel Ratio Sensor Circuit Response Malfunction (Bank 1 Sensor 1)

P1135
Air/Fuel Ratio Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)


Sounds like the type of problem that will take an independant shop forever to diagnose but lexus seconds.
You may want to weight your options carefully.

Fern

Silversport01

Are they talking about the O2 sensor? If so that would make your car stumble.

LexusTech

Needs air/fuel sensors...in laymans terms the oxygen sensors mounted on each exhaust manifold,before the catalytic converters. That P0125 is related to the air/fuel sensor codes because they share an electrical circuit.

There's a similar thread here https://www.clublexus.com/forums/sho...hreadid=103353