I have an EVAP dtc... I don't remember what the Codes are, but I will get them and post them if no one is able to give the answer just from the clue which follows:

When it is warm/hot outside, the Check Engine Light is on, but when it gets cold outside, it is off.

Essentially, in the Fall when it was warm outside, the CEL was on all the time, yet when it got cold over Winter, it went out and stayed out until it got up into the high 60s and 70s again, and then it came back on.

What part of the EVAP system would fail under these conditions?

Thanks in advance for any info!

Anthony

 

EVAP Codes are like P04XX.

Not sure exactly what your condition is, but usually I will get a code like that when the gas tank is low, but it's rare. It might be a problem with the gas cap, but let us know the code.

 

Ill bet you have a P0440, i had one for about a year with the same symptoms... its a evap code.. for the rear VSV valve on the charcoal filter at the back.... if thats the code...

Lexus is over $900 for the replacement charcoal filter.... somewhere there is a thread on here by me with the part number for just the valve.. it comes off the corolla i believe its about $150...

I fixed mine about 6 months ago... no code came back....

 

Wouldn't you know it, I went to Advantage Auto and had them plug in, but the Engine Light had gone out that day, so no DTCs were present... I know there were 2 codes there last fall and I DO think that P0440 was one of them... And perhaps P0441, but I don't remember. Due to the recent cold snap up here in Northern Ohio, the Engine Light has not returned yet.

On a brighter note though, yesterday evening I had to drive up to Auburn Hills, Michigan, a 3 1/2 hour trip. I set the cruise control at around 76-77 MPH, and my average MPG topped out at 26.0! I didn't reset it or anything, just let it run... I usually average 25.2 - 25.3 MPG. I'd guess that I am getting nearly 30MPG highway!

Thank you Leines for that information. When that troublesome CEL comes back, I'[ll be sure to get the Codes read!

 

Ditto to what Leines said. I think we were in the same thread. Depending on what year your RX is, the problem may be caused by a faulty vacuum switching valve (VSV) and/or rotting vacuum hose. In my 1999 I fixed the problem, but learned during the process that soon after 1999 Lexus changed cannisters to one without separately-available VSVs. Or at least that is what I think I concluded.

 

Ok, so I discovered that the nearly 26 MPG Average I was getting was incorrect... That was the Average MPH... I am getting about 14.8 Average mpg. Is this right or is there something causing a serious drag on the engine causing this? When I go to the instant MPG on the highway, it bounces between 14 and 25 with about 18-19 at the average.

 

14.8 mpg is terrible. Check the sticky thread at the top of the forum sub-topic. There are many tips in there to improve mpg.

For comparison, I get 18-19 mpg city, and 23-24 mpg highway.

 

So yes, got my codes diagnosed... P0440 and P1130. Working on getting things figured out now... Found a post here about the P1130 and found a good price on new Denso A/F Sensors through Amazon... now just need to figure out the P0440.
Hypervish- As an update for my fuel economy, the majority of my driving is somewhat hilly highway, and have been keeping the instant economy display on so I can monitor the economy on my way to and from work. I have about a 40 minute drive each way (+10 to 15 minutes on the way home in rush hour) and the average rate of travel on the highway is 60 to 70 mph... Up hills is wen I am hitting (occasionally) that 14.something mpg, but it is averaging about 19 to 23 on the flats... I love when I let off the gas going downhill and it hits 100mpg!
Perhaps when I replace the A/F Sensor my economy will increase.

 

http://www.obd-codes.com/p0440

 

Thanks for the link!