Like the title suggests. Periodically if I drive briefly spiritedly in manual mode with sport and come up to a stop light, I can feel and see the tach showing the engine resting into a lumpy idle.

This usually occurs when I have no AC or headlights on, so limited load on the engine. I can blip the throttle a little and get the engine to settle down. I also put the car into neutral when stopped as well, so like I said, low load.

Please note I have a 5 mile commute, not the best for warming up. It reliably happens at the exact same stoplight when returning home from work. When driving slowly I get no such issues.

I'm stumped that the car doesn't throw a CEL. I figure if I had a bad coil pack or nasty spark plugs causing misfire that a CEL would be present.

Its almost like the spirited driving before a stop light messes up the fuel trims. I haven't noticed much difference with major temperature changes.

I'm stumped.....

Any thoughts? (yes, I know, let her warm up more...)

 

How cold is it there?

Yes let her warm up before you start mashing it(3 bars)

I'd got to an auto parts and check to see if the car threw any codes. If not pull the fuses to reset it

 

Cold cycle is brutal. Try a bottle of Techroline or equivalent if you don't get the car into closed loop much.

 

Ya since my baby sits outside I can affirm that the cold start up is nasty. It wastes so much gas also.

 

Good idea! Thanks.

 

Are codes thrown when no CEL is present?

(still a good couple of ideas)

 

I've only seen codes thrown when there is an accompanying CEL. I've also thrown a CEL and the ECU eventually disregarded it and cleared it's own code after x miles.

For a lumpy idle I've personally seen that (in other cars) with either bad gas, bad plugs, or a cold car. As a test just sit in your car until it warms a decent amount this next time. Then see if things are any different.

 

Yes, there can be DTCs set without a CEL. There are also "pending" DTCs that can give you a heads up on something close but not quite right. You'll need a better than average scanner to see this stuff, and it should ideally include Lexus/Toyota specific codes in case there's something really odd going on.

 

Sigh.... why did I sell my ODB2-USB cable.......



I'll borrow one from "The Zone"