RPM Drop Problem
 

Past couple of days I came across this weird behavior of dropping RPM. Here is the senerio. I have a 6 Speed manual. When I put the car in neutral from a gear, lets say, when I am stopping for a traffic light and I have to engage the clutch, the RPM drops to around 450 -500 for about a second and then jumps back up to normal (around 800 RPM).
Here is whats bugging me, I noticed this only happens when it is very hot (temperature of 100F or more). When the weather is nice (80-90F) this is not an issue. The RPM does not drops below 800.
I am just wondering if anyone can think about what could be causing this. btw, I have 143K miles on my car. Got the first 105K service at 80K, second at 135K, but never got valve adjustments.
Anyone can help be narrow down the problem:
Dirty throttle body?
Vacuum line leak?
Valve adjustment?
The only thing that has me confused is why does this only happens when its very hot.
Thanks in advance.

https://pic80.picturetrail.com/VOL83.../388514054.jpg

Disconnect the battery for a good 30min or so.

Below is the procedure from the 1999 TL Service Manual

COMPUTER RELEARN PROCEDURES
1999 Acura 3.2TL
GENERAL INFORMATION
Computer Relearn Procedures
All Models
* PLEASE READ THIS FIRST *
The following general procedures are to be used if
driveability problems are encountered after power loss or battery has
been disconnected. These procedures may provide an aid in eliminating
these problems.
To reduce the possibility of complaints, after any service
which requires battery power to be disconnected, vehicle should be
road tested.
COMPUTER RELEARN PROCEDURES
Vehicles equipped with engine or transmission computers may
require a relearn procedure after vehicle battery is disconnected.
Many vehicle computers memorize and store vehicle operation patterns
for optimum driveability and performance. When vehicle battery is
disconnected, this memory is lost. The computer will use default data
until new data from each key start is stored. As computer memorizes
vehicle operation for each new key start, driveability is restored.
Vehicle computers may memorize vehicles operation patterns for 40 of
more key starts.
Customers often complain of driveability problems during
relearn stage because vehicle acts differently then before being
serviced. Depending on type and make of vehicle and how it is
equipped, the following complaints (driveability problems) may exist:
* Harsh Or Poor Shift Quality
* Rough Or Unstable Idle
* Hesitation Or Stumble
* Rich Or Lean Running
* Poor Fuel Mileage
These symptoms and complaints should disappear after a number
of drive cycles have been memorized. To reduce the possibility of
complaints, after any service which requires battery power to be
disconnected, vehicle should be road tested. If a specific relearn
procedure is not available, the following procedure may be used:
Automatic Transmission
* Set parking brake, start engine in "P" or "N" position.
Warm-up vehicle to normal operating temperature or until
cooling fan cycles.
* Allow vehicle to idle for one minute in "N" position. Select
"D" and allow engine to idle for one minute.
* Accelerate at normal throttle position (20-50%) until vehicle
shifts into top gear.
* Cruise at light to medium throttle.
* Decelerate to a stop, allowing vehicle to downshift, and use
brakes normally.
* Process may be repeated as necessary.

Manual Transmission
* Place transmission in Neutral position.
* Ensure emergency brake has been set and all accessories
are turned off.
* Start engine and bring to normal operating temperature.
* Allow vehicle to idle in Neutral for one minute.
* Initial relearn is complete: process will be completed during
normal driving.

Some manufacturers identify a specific relearn procedure
which will help establish suitable driveability during relearn stage.
These procedures are especially important if vehicle is equipped with
and electronically controlled automatic transmission or transaxle.
Always complete procedure before returning vehicle to customer.

I'm having the same issue but usually when I have my AC on. I took it to the dealer and they said they can't do anything cuz there's no lights coming up.

I noticed this when I unplugged my battery for my HID install. It takes a few miles of driving to get it righted. (i didnt follow or know about the ECU procedure).