It's been hot in California! My 1999 RX300 runs smoothly when cold and warming up. Once warm, it will stumble off idle when starting to accelerate. Maybe around 1000-1500 rpm range. below or above that, it seems fine. If I shut off the engine for a few minutes, then restart, the problem is even worse (I'm assuming because of heat soak).

I just put in new NGK plugs and Denso coils ($40 for the plugs, and $350 for the coils), still the same issue. I replaced the Idle Air Control Valve a year or two ago with an OEM part also.

I'm stumped? Do you guys have any suggestions?

Thanks for any ideas!

 

When I had a stumble off idle it was a VVT issue. I cleaned the screens and changed the solenoids.

VVT DIY is https://www.clublexus.com/forums/rx-...ement-diy.html

 

Are you getting CEL? I am not in favor of throwing parts to get to a happy answer. Plugs [110K miles service item] may have been ok but coils without CEL may not have been necessary.

Salim

 

No vacuum leaks? Throttle body cleaned lately?

 

No Check Engine Lights. I cleaned the throttle body when I did the MAF about two years ago. I have not closely checked for vacuum leaks. What's the best way to do that? Starter fluid? That makes me a little nervous!

I tried to purchase VVT's last night on Amazon and O'Reilly auto parts, and they're telling me that it can't be shipped to my address (San Diego, CA). Is there possibly something in these parts that CA doesn't like? I've had this problem before when purchasing shower heads (CA low flow restrictions).

 

Can't think of anything special about these parts.
Note cleaning the screens may be sufficient, and if I remember correctly you can do that without removing the solenoids.

 

I'll try cleaning the screens to see what happens. Thanks for the tip.

FYI, I did some digging regarding the Amazon shipping thing, and apparently certain parts have to be California approved for emissions (CARB). If a retailer, like Amazon is uncertain about a part, they just won't allow it to be shipped to a CA address. They'll only ship parts that have been "certified" by the manufacturer for CA compliance.

 

Wanted to give you guys an update on my rough-running car. I checked the VVT screens last weekend, and they looked almost perfect. Once again I was disappointed.

Then yesterday afternoon, the car started running extremely rough. Barely idling, and almost no vacuum (brakes had almost no assist). Then a great thing happened...I got the CEL! It was P1349. Intake bank VVT problem. Pulled the VVT, ran down to O'Reilly's and got a new one for about $79. Put it in, cleared the code, and everything is working perfectly!

Thanks again to all of you for the help!

 

Glad you found it and it's resolved. Thanks for the update, it can help the next guy with a similar issue.