High idle/rough idle

Hey guys, anybody have answers about idle rpm's for 3rd gen?
When it's below 45 deg I cant get engine to idle below 1100 rpm until I've driven a few miles. Even after letting it warm up for 20 min. Then when its finally idling normal after driving (800 rpm) if I shut it off for 10 min and restart it, it's back to 1100 rpm.
Is this due to the catalytic converter temp sensor? Creates a hard shift when putting it in drive most times. Sometimes jumpy when trying to stop or ease into parking space.
Also experiencing occasional rough idle when stopped in gear.
Almost 8000 miles on truck, but this is first cold weather experience with it.
Any wisdom or informed opinions appreciated. Thanks!

 

The new Tacoma’s run a valve cleaning cycle triggered by factors sensed by the ECU. Mine does this at random when I start it up. It revs higher and the exhaust note changes. I wouldn’t call it rough, but it’s got way more bark to it. Typically it lasts about a minute then goes back to normal.

What is happening is the engine is dumping fuel via the manifold injectors to clean deposits off the intake valves that are not cleaned when the engine runs off the direct injectors that spray right into the cylinders.

Hope this helps.

 

Thanks for the input. I've heard of this but I thought the cleaning cycle would not last 20 min and repeat every start up... do you happen to know how long the cleaning cycle runs for?

 

Mine seems to be around 1 minute or less. Yes, yours sounds like a different issue.

 

:/

 

According to the literature, the cleaning cycle can last up to 10 minutes.

 

When I had mine, in cold weather and snow it acts like all engines... it "chokes" (reduced air) and bumps idle up until it gets to a preset temp. It could take a few minutes but I have had it take over 20 minutes. Depending on temps and conditions.

 

Maybe your AC is on. Defroster automatically turns on the AC without the green light coming on.

 

You have an OR, is your foot on the brake when you are noticing the high idle? If so, its your brake booster. Give it a shot, put your foot on the brake pedal for a min and watch the idle, take it off and you'll notice it idles below 1k.

 

It's fine, I wouldn't worry about it. Plus there's no reason to let it idle for 20 minutes

 

Interesting, never heard this before. Where did you read this?

 

Been like that for years and years...

 

This sounds like a typical cold start cycle. The engine will burn a little richer to help get everything up to operating temperature. I find these engines shed heat quickly when shut off. So on restart the cycle begins again. With an automatic you will definitely feel it when engaging gears and at slow speeds. If idle returns to below 1000rpm after some time driving then I would say the system is functioning correctly.

A/C with defrost has been common for well over a decade on most vehicles. It uses the A/C evaporator to remove moisture from the air then heats it with the heater core to dry the windshield faster. Even when A/C is shut off it will override it.

 

Wow. You're right! If I turn the heater off it drops 200rpm. Thank you!

 

Yep. Been like that for a while. Whenever i start the truck, i let it go through it's cycle before moving. Done this with every vehicle I've owned. Definitely agree with it cooling down quickly, although i don't usually start and restart the engine that quickly unless I'm running errands, but even then the rpms will drop off. Also have to let the transmission warm up. Any weird movement or shifts I've experienced within only a few minutes of startup

 

Sport does this also, even though it doesn't have the electric brake booster... only when not up to operating temp though.

 

Thanks for the support guys. Just something I've never noticed in an other vehicles, but this is by far the newest vehicle Ive owned. Cheers!

 

There's a direct injector cleaning cycle on these engines, which really has nothing to do with the cold start stuff you're asking about. I think your questions have been answered pretty well in this thread but just so there's no confusion... the DI cleaning cycle is that loud ticking racket that happens at random when at hot idle. The ECM decides when and for how long it runs (seconds or minutes). As soon as you touch the gas and start driving, it also cancels itself.