Hi, All
It is so weird. I posted the tread about 4G cold start heistation last year around June. I used top tier fuel and used Lucas something to clean up maybe carbon. but they did not work. I ended up with changing to WIX filter, then all the hesitation just gone.

Now It CAME BACK at last week. I replaced the filter again. but this time it did not work. the cold start hesitation stays. I feel like it happens only when the season is changing. the temperature varies between day and night.
I doubt that maybe the sensor telling the ECU the temperature can not read the correct data in the morning at this changing season? it is so weird, last year, after changing the filter, it did not happen until now, even in the coldest NH winter.

1. Does 4G have Intake Air Temperature sensor? or it is integrated in the Mass air flow sensor?
2. I took out the MAF, it looks clean and good.
3. I do not have idle problem, smooth when car is idle.

Do you gays have any idea?

the video was shot last year. the symptom is exactly same as last year in the video.

 

Please Help~~~~~
no one?

 

from the VERY short video, sounds like the starter.

fuel, spark, air. it's getting fuel, it's getting spark, it's getting air...

 

Really appreciate your reply.
last year after end of June, I replaced the air filter, this sound gone away until now. but for last year, this hesitation came suddenly at a certain day until air filter replacement.
if the starter, it started very well in the winter, no hesitation at all no matter cold or hot start.

1. is it possible the carbon buildup? or injector? my car is 45,000 miles, but basically no local driving, maybe 10% local.
2. sensor check the temperature and send to ECU ? I just cleaned the MAF by using CRC MAF cleaner this morning. does not look like help.

 

nice! i didnt think of injectors! it could very possibly be at start up, an injector isnt spraying correctly and causing that hesitation.

 

i just cant think of why temperature would affect it.
maybe if we continue to think out loud, we could brainstorm and come up with more ideas on why you're having a slight hesitation at start up

 

I feel like the more time the car sitting, the more severity the hesitation will act. so the most hesitated moment is in the cool morning.

Why My suspicion is on the Temperature, because consider to last year, the hesitation only came at season changing period. this year came at last week. if continue to be cold or warm, it is fine.
I am keeping thinking of some certain sensor can not read the right temperature data to ECU, so the ECU can not inject the precise fuel amount to mix with air when cold start?
or buildup on injector, so the injector can not give the amount of fuel the ECU ask for when cold start? (this not make a lot of sense to me, if it acted this way, I would have hesitation in past winter after air filter replacement every morning)

 

right, if you would have a bad injector, it would be bad all the time..( i think)

 

https://acurazine.com/forums/third-g...hanges-631749/


I found this thread from 3G. sounds like making sense to me and my scenario? reset the ecu when environment change. wake up the computer to let her know it is not winter anymore or not summer anymore~~~~. Cause the cold start hesitation only happened to my TL at the time of season change~~~~.
Do you guys normally disconnect the negative of the battery routinely?

 

hi I know this is an old thread but did you ever fix your issue?
my 2014 TL is doing the same thing not as much as yours but maybe once a week sometimes once a month it varies

 

HI,
I never had issue figured out, and it was more than slightly at the morning mostly happened in April mornings and September mornings, which has big difference on temperature between morning and night.
when the issue first happened , the car was at around 40k miles and its 5th year. I could never thought about the timing belt or serpentine belt. the reason I said that is two months ago I had it done the timing belt service including the serpentine belt. as of now, I do not have it happened again since then. I know it is weird. but maybe check your serpentine belt? or if you are at the point need to do the timing belt service.

 

I had same issue. Timing Belt and Serpentine Belt and was sound is gone. The sound only happened in Winter and on start but once warmed up, the sound was gone.