Prolonged high idle at cold start?

I had a random bad hesitation on acceleration , and was told to " clean throttle body, and / maybe mass air sensor ". I did both- the hesitation is cured , but , now it has a prolonged high idle at cold start lasting a few minutes. I keep truck in garage , air temp is generally around 40. any ( helpful }suggestions ? and, yes, I,ve already thought of beating the crap out of it with a hammer, so don't go there....

 

Sounds all normal for cold start operation. Define prolonged? Ever time it, should only occur on cold start defined as cold engine not cold ambient temperature. What year? Engine?

 

2010 , 4 cylinder .- 1100 ish rpm for several minutes -calms down to 6 -800 rpm. I,ll time it later

 

After cleaning the throttle body it can take a little bit for the idle to settle down into its sweet spot. Take it out and drive it, stop at lots of stop-signs with your foot on the brake, turn the a/c on and off, cycle the steering wheel lock to lock. All of those things will force the adaptive idle to relearn quicker

 

the cleaning was done 11-28-18 . 1000 miles ago . I have since replaced the air cleaner filter , and recleaned mass air thing in December. I did not remove throttle body for cleaning , maybe I should ?

 

If this only on cold start, not cold weather, just first time in the morning on a cold engine then t sounds perfectly normal. I have a 4.0 but it does the same thing.

 

Removing and cleaning both sides of the throttle plate is always a good idea. Probably not going to affect the hi idle youre experiencing though. Honestly it could be normal, as it does eventually settle down to 600-800. Any check engine light/codes?

 

no check engine light - before the cleaning, the idle calmed down in under a minute. I notice it cause its a 5 speed

 

how high an idle are we talking?

 

Read five posts above yours

 

The duration of the high idle will vary based upon ambient temp and how long it takes the engine to reach normal operating temps. But day to day with same morning temps you should not notice a difference if you time it.

 

ok- its 32 degrees out - truk has been sitting for 2 hours , I timed it
start up 1500 rpm -( after 1 minute idling , 11-1200}
- (2 min., 1100 )-( 2.5 min, over 1000-) (3 min, 1000 ) -(4 min, 900 )- (5 min, 800 ) (- 6.5 min, 700)====all sitting idling

 

This may be a long shot, but... try disconnecting your battery overnight, and then reconnect it first thing in the morning before you start it up. I just replaced my battery and did the reconnect first thing in the morning, when the engine is stone cold. The cold start RPM was noticeably lower than it was before. Of course, after a battery disconnect the computer will have to re-learn all the fuel trims similar to what b_r_o said in post #4 above... not sure if all that stuff is necessary (cycle A/C, turn steering lock-lock, etc) but any battery disconnect will require this re-learn procedure for the fuel & emissions system.

 

Battery disconnect wont hurt. But its not the fuel trims that need to stabilize, its the actual position of the throttle plate. When you clean the throttle bore you're making a bigger path for air to flow through. The throttle plate needs to adjust (electrically) and pinch off the air flow.

Adding a/c and turning the steering wheel require the pcm to bump up the idle speed, this forces a relearn quicker.

 

A whole lot of nothing OP. Stop stressing over something that is completely normal.

 

Sounds like your truck is running as it should...

 

I,m pretty sure I,ve done the battery thing, but will try again overnite - thanx

 

Agreed.. i know OP is wondering why its different now after the cleaning but its not really a problem, just different

 

I’d put some garlic over the hood and a cross in the garage. Might help as much as the battery hocus pocus

 

really - 5 - 6 minutes to get lower / possibly normal idle ????? I think you r waaaay wrong , but thanx for the input.