Problems with part-throttle/steady state surge? Maybe I can help.

If your car surges at part throttle and only in a certain speed range, there's an easy fix. It is probably not a bad MAF/MAP and probably not a mechanical problem. It is a TCC problem that can be fixed in two easy steps. 1: fix your stock TCC PWM minimum and maximum. 2: disable TCC from locking in third gear.


1: These are the stock TCC pulsewidth minimum/maximum tables. It is (at times) commanding as low as 20% duty cycle. This is what is causing your part-throttle surging problem. Mine was most obvious with a duty cycle of 40-45%.
http://i205.photobucket.com/albums/b...ps2718ecfd.png

Here is the fixed TCC pulsewidth table. 90% minimum and 100% maximum will completely eliminate your problem, if it was indeed caused by the TCC PWM.
http://i205.photobucket.com/albums/b...ps321d3335.png

2: Once you change the TCC PWM problem, you're not done. Changing those tables will introduce a neck-snapping lock in third gear that will make your car buck like a manual transmission that you let off the clutch too quickly with no throttle. It wasn't noticeable in fourth on my car because the torque convertor locks as the car shifts into 4th gear. So our next task is to disable the TCC from locking in third gear. That can be done here, in the tables highlighted red:

http://i205.photobucket.com/albums/b...psnnuaegtt.jpg

Once done you should have something like this:
http://i205.photobucket.com/albums/b...psxglsuvim.png

YAY! NO MORE SURGING! I chased this problem for more than a year over-thinking it. "Is it my unfiltered card-style MAF? MAF-only tune? Injector offsets got changed somehow? Spark plugs? O2 sensor? Voltage surging?" Nope. Just the TCC PWM.

Update:

This was done probably a year(and maybe a half???) ago. I drive a LOT of miles every week plus vacation. Still no negative side effects so far. TCC still locks firmly, no surging or shift problems, consistent trans pressures. In case anyone was wondering.

Will this work on none stock convertor? Thanks for sharing this, looks great.
Thanks John

As long as it has PWM for the TCC then it should, yes. Aftermarket converters in theory have better internals too.

Followed your instruction to the letter, and it does look like some improvement, have about 100 miles on the changes. My problem was TC was locking up in 3rd at slow speed. The only different was my max number 256, could be because of different version of the software. Thanks John

Basically as long as you disable the torque converter lockup in 3rd you'll have a more enjoyable ride. Mine was really bad with the lockup at stock settings lol.