RPMs Bouncing after Cold Start (1 Viewer)

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Joined
Nov 6, 2016
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Location
North Carolina
Hi-

After a cold start, I am having an issue with RPMs "bouncing" up and down rapidly. The bouncing is so severe it causes the truck to buck really hard forward and back - you would definitely notice it if you were following in another vehicle. It happens every cold start and occurs after about the first 1/8th of a mile. The Toyota dealership said they looked at the computer and didn't see any issues. Any thoughts? Any ideas or suggestions would be MUCH appreciated.

Here is some additional info in case it helps:

  • It is a 2008 LC with 130,000 miles. I have had the LC for two months and its just been happening the past month.
  • Typical RPM range when the bouncing occurs is 2,500 to 3,000 with the tachometer jumping quickly up and down by roughly 500 RPMs.
  • It lasts for about 10 seconds and then does not re-occur again until a completely cold start (i.e., overnight).
  • If I let off the gas, and wait a few seconds before applying the gas again it usually stops.
  • A week before this started happening, I had part of the 120K service completed:
    • Oil Change
    • Transmission fluid change
    • New Spark plugs
    • New Serpentine belt
  • It has occurred at all outside temps over the past month (45 – 80 deg) – located in southeast US
  • Again, it is is not a minor revving up and down, it is severe with the entire vehicle lurching front and back.
Thanks!
 
Did you have the transmission fluid change done at a Toyota dealer?

HTH
 
Did you have the transmission fluid change done at a Toyota dealer?

HTH
No, the transmission fluid change was done by an independent shop and it sounded like the mechanic had a hard time figuring it out. Is there something related to this that you think I should have checked?
 
No, the transmission fluid change was done by an independent shop and it sounded like the mechanic had a hard time figuring it out. Is there something related to this that you think I should have checked?

Yes. According to Toyota's online Technical Information System (https://techinfo.toyota.com/techInf...urce_url=https%3A%2F%2Ftechinfo.toyota.com%2F), the transmission fluid change is not a simple procedure. It involves an exterior hard pin bypass and internal manipulation of valve states (open/close) using Toyota's TechStream software on a computer.

My understanding is that there are valves inside the transmission that open/close based on fluid temperature. In order to properly replace the transmission fluid, these valves need to be manipulated during the process of replacing the fluid. Failure to do this properly may result in an incomplete fluid replacement, underfill, overfill, etc.

It is easy to imaging how an independent shop could botch this job.

My guess is that the symptom you are seeing is not your engine, but your transmission. Based on your description, it sounds like when the transmission is cold, you experience the symptom when the transmission warms up a bit, then goes away until your next start when the transmission is cold again. It sounds like this could be caused by improper fluid distribution inside your transmission - possibly caused by an improperly performed fluid change.

If I were you, I'd go to the dealer, explain the problem and see if they can either "fix" the problem by manipulating the internal valves, or at worst, performing another transmission fluid change - this time properly.

HTH
 
Yes. According to Toyota's online Technical Information System (https://techinfo.toyota.com/techInfoPortal/appmanager/t3/ti?_nfpb=true&_pageLabel=ti_home_page&contextType=external&username=string&password=sercure_string&challenge_url=https://techinfo.toyota.com/techInfoPortal/login/techinfo&request_id=5633168302675176354&authn_try_count=0&locale=en_US&resource_url=https%3A%2F%2Ftechinfo.toyota.com%2F), the transmission fluid change is not a simple procedure. It involves an exterior hard pin bypass and internal manipulation of valve states (open/close) using Toyota's TechStream software on a computer.

My understanding is that there are valves inside the transmission that open/close based on fluid temperature. In order to properly replace the transmission fluid, these valves need to be manipulated during the process of replacing the fluid. Failure to do this properly may result in an incomplete fluid replacement, underfill, overfill, etc.

It is easy to imaging how an independent shop could botch this job.

My guess is that the symptom you are seeing is not your engine, but your transmission. Based on your description, it sounds like when the transmission is cold, you experience the symptom when the transmission warms up a bit, then goes away until your next start when the transmission is cold again. It sounds like this could be caused by improper fluid distribution inside your transmission - possibly caused by an improperly performed fluid change.

If I were you, I'd go to the dealer, explain the problem and see if they can either "fix" the problem by manipulating the internal valves, or at worst, performing another transmission fluid change - this time properly.

HTH

Gaijin - I really appreciate your help! Its at the dealer now - hoping this is it and not a bigger issue.
 
Gaijin - I really appreciate your help! Its at the dealer now - hoping this is it and not a bigger issue.

I hope it's an easy fix - please let us know how it works out.
 
So problem is fixed. It was low on transmission fluid. Dealer added 2 qts of ATF. 3 days in and it is back to normal. Thanks for the help!

Great news, congratulations! I love it when a plan comes together :clap:
 

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