My vehicle is 1999, Lexus Rx300(SUV) with 117K miles on it. The engine vibrates a bit rough when idling with the door and the steering wheel shaking. So I tried Auto-RX(cleaning phase) last week.(Castro GTX conventional and the filter is Fram) After 100 miles or so, CEL came on and the code said P0330(Knock Sensor Circuit Malfunction?). I became worried and went to my mechanic. He said that this particular code comes on when wrong(thinner) oil is added to the car and recommended that I change the oil immediately back to Mobil 1 10w-30. In fact the oil taken out was like water. After that, the CEL stayed off when I dont go over 60MPH, but comes back on when I go high-way. As is the often case with P0330, the gear does not shift to over-ride.
After that, I learned that this website says that Check Engine Light does come on during the process and it will come off naturally.
What I would like to ask is that is it wise to go ahead and start over the cleaning phase again? In that case, this code is normal or typical one in cleaning phase? or any of you have any idea as to about when this code typically goes away? Or just keeping the current Mobil 1 oil makes the light go off at some point? (Or, on the contrary, keeping the full-synthetic oil like this is actually not good because it makes the dirt stay around the sensor? )
I did a research through discussion board but those useful posts were not available,,,
Thank you very much in advance!
-- Edited by hide09toshi on Monday 29th of November 2010 03:53:37 PM
I've already replied to your email, but will respond here for the benefit of others.
This is not an uncommon occurrence. The sensor gets fouled. It typically cleans up during the rinse phase. Your mechanic had the best intentions, but was ignorant of typical oddities when using Auto-Rx.
Mobil 1 is not recommended due to the use of PAO and the di-esters that are required while using it as a base stock. There are lots of synthetics out there that do not use PAO, POE, EOP, or any of the exotic base stocks. Pennzoil, Castrol (except the 0w-30), Delo/Havoline/Texaco/Chevron, Citgo, Mystic, ..you name it, if it's on the shelf and NOT one of the Mobil 1 products, it will most likely work well.
The main reason we recommend conventional oils is due to cost. It's your call, but 2500-3000 miles is a short oil interval for the dollars spent. Something like a turbo'd Euro, then sure, it makes sense to spend the money for Rotella 5w-40, but otherwise go cheap; on both oil and filters.
A thing about synthetic oils. They mostly endure insult better or longer than conventional oils. They're not "magic" oil. In fleet use, synthetic deliver NO SIGNIFICANT difference between overhauls. What they provide is less down time. Now your engine may indeed specify a synthetic oil, but that too will typically come with some protracted mileage recommendation. Not all, surely, but many. The owner of some higher end Euro alloy could be served just as good (in many cases) with conventional oil over shorter durations. This assumes that the oil met certain criteria, and if one owns a higher end Euro, I doubt that you're worried about cost ...but I hope I've communicated the point clearly here ..there is no such thing as "magic oil".
-- Edited by geeaea on Thursday 2nd of December 2010 07:12:29 AM
The conventional 10W30 Catrol GTX would not appear any more to pouring like water than the Mobil 1 10W30. I am not sure about the 1999 model, but I believe that this motor has a device that regulates variable cam timing. Its a nice feature to get the most performance out of a motor at all rpm ranges. This device is controled by oil pressure and it does have its own filter screen.
If the screen was dirty and began to clean up and allow more oil to pass through, this would likely confuse the on board computer and spit out the code. Simply because the computer got new information and didn't have enough run time to adjust.
It is possible that your transmission is perhaps dirty. Perhaps a sensor is not telling the computer to make the final upward shift into overdrive. Or perhaps a shifting valve is sticking. When was the transmission last serviced? Your throwing away alot of fuel without the overdrive function.
Those are two posts about the P0330 code, a fairly common code for the 3.0l engine that is in the rx300, sienna, avalon, and es300. In the case that your code does not go away you will need someone to replace the sensor and while they are back there (in the back of your engine) you will want them to replace those spark plugs, which should help your rough idle.
If the code does not come back but you still have the rough idle you might try replacing the air filter and ignition wires as two things that you can do yourself fairly cheaply since replacing the plugs is very labor intensive on that car.
