1999 RX300, 145K, full tank of gas, strong battery, new plugs. Sat for about 10 days, now hard to start (cranks well but doesn't start easily) and once running won't idle. Likely cause? TIA.

 

Did it run well prior to sitting for the ten days, after the plugs were replaced? Was the throttle assembly and upper manifold removed the install the rear plugs?

Does the dash warning light indicate a check engine warning? Does the circuit self-test ok?

Were all the vacuum lines reconnected according to the diagram on the hood?

Any chance of water in the fuel?

Air cleaner filter, hose and box reasonably clean inside?

 

Car ran fine 10 days ago. Plugs were changed about 6 months ago. No work has been done in the engine compartment since then. No check-engine-light.

 

It could still be the battery, and best to take it out on the highway to get it a full charge. I use an Optima Red Top and even though my little RX sleeps during the week, it is fully ready to go on the weekend. However, I have had a few friends that let other vehicles sit for like 2 weeks and some issues with theirs batteries similar to what you describe. It would not throw a CEL in this case.

 

Without any errors indicated, it leans towards electrical symptoms.

Insure the battery has a good charge. Have it checked at a parts store for internal shorts indicating an old or defective battery.

Has the clock reset on the blue interior screen? When batteries go low, at times, there is an indication of resetting the clock.

 

It happened to mine 2 years ago. It hard to start and idle went back to zero right after it started and stall. I have to gas it to keep the idle up. Dealer replaced idle speed control ($400)and the problem fixed. Good luck.

Francis 99' RX

 

i got the same problem also .. i got my replace today for 260 plus labor .. and the problem stop

 

You can have the dealer replace the ISC for $400. An alternative would be to clean the ISC/throttle body yourself. It'll cost you about 1.5 hours and a $5 bottle of carb cleaner. I've posted instructions here:
http://us.lexusownersclub.com/forums...howtopic=30723
I cleaned it myself and now my car runs like it is brand new. Cheers

 

yea i tryed to clean it .. i took it to my buddy that work at lexus .. they tryed to clean it i didnt really help and so i took to my other buddy that own a auto repair shop he had the car all day he took everything apart cleaned it didnt work .. so i said forget it just replace it .... 260 was a good price

 

Further thought: this only happens when the engine is cold, which suggests to me that the problem is more likely with some temperature sensor rather than the idle control valve. Thoughts?

 

at 145K i'd guess that it was some minor instrumentation problem, like JAB just said, it's probably something like a false temp. reading that's throwing your starter off.

 

http://us.lexusownersclub.com/forums...howtopic=30723

check out this link on how to and read my recently posted post about an easier way, it just may fix your problem and only for a $4! will take probably an hour from start to finish!

 

Yup, it'd be worth it to take a look at that posting (since I did put it together ). Let me know if you have any questions on that. Im so glad i toook it apart cause it saved me lots of $$$ and my car runs like it's brand new now =]