Okay, here is a quick synopsis of what has happened with my wifes' sisters 2002 rx300 with 150K miles...
First off, I've been working on cars most of my life and have a decent level of "car knowledge", but this has been a difficult
road since my sister in law doesnt know car's and I've had to try and pick her brain on the matter while I run my diagnosis, and it has been a rough
road.
Okay, she is driving down the highway on cruise control, goes to slow down for her exit, and the engine stays revved at around 2500 to 3K
rpm's. She comes to a stop at the light, and it is still doing it. She drives the 30 miles back home, with it doing this. Also the engine check
light is on.
She leaves it with me the next day. First thing I do is hook up my obdII scanner to run the codes. I also notice the VSC trac light is staying lit and the
center console button wont turn it off. I ask her about this and she says it is always lit and that the button is a "dummy" button.
I'm scratching my head on that one, but continue my diagnosis.
Scanner comes back P110, which is intake temp sensor. so I pull the MAF temp sensor and put on a new one. It still runs the same.
So I reset the ECU by disconnecting the battery neg cable. Still runs the same. However, NOW the VSC light is off, and I can turn it on and off with the
button, lol.
So I take the MAF sensor back to get my refund and put the old one back on. Now the rev's are rising and falling instead of just running at 3K.
I do another reset on the ECU, and now it is idling really low, like 3 or 400 rpm, and dies when backing out the driveway or coming to a stop.
So, I do some reading on here and find the IAC valve is a common dealeo. I take everything apart, clean it thoroughly, and as I'm putting everything back
together, I find a loose vacuum hose that connects under that plastic engine cover. I'm 100% certain I didnt accidentally knock it loose, as I'm very
careful and take my time, plus they are hard to pull off anyways.
So now I think I've got it cured, and go to start and it runs GREAT! Idle around 900, good power, perfect.
However, now I have another check engine light, which comes back as 1155, 02 sensor....
Could the 02 sensor be the problem? Even though now it runs great? I have tried reseting the ECU a few times, but this check light is still there.