Help diagnosing weird issue, maybe torque converter related?

Recently bought a 2001 2.7L 4x4 Automatic

I need some help finding a strange issue I cant pinpoint.

When coming to a full stop at a stop sign or stop light, the idle drops down to around 700rpm when I am stopped and on the brakes. After about 5 to 10 seconds, the idle drops further down to 550rpm-ish, and a shudder/vibration can be felt while sitting in the truck. If I put it into PARK when sitting at the same stop sign, the rpms will return to 700 and the shudder goes away. The drop in rpms and shudder only seems to occur when sitting at a stoplight in drive, with my foot on the brake. Upon lifting my foot off the brake and accelerating, the shudder goes away and only returns upon stopping again.

Once again, the shudder goes away, and rpms return to their normal 700 range when putting it into PARK or NEUTRAL.

I have owned a 2nd gen, but this is my first 1st gen and im not used to this auto trans in it. My concern/idea is that the torque converter solenoid is bad, and causing the torque converter to be locked up constantly, which would mean when stopped in drive with my foot on the brake, the additional load from being stopped causes the engine rpms to drop and studder. Upon putting it in park, it released the load from the brakes as the trans spins internally now.

I also did a test, and FULLY pulled my e brake cable as far out as it would go. I watched the mechanisms at the back wheels, and they both move and engage freely. Upon pulling the ebrake, the truck slows down to a very slow crawl, but does not quite stop moving. I dont know if this is a poorly adjusted e brake, or if the additional load from the torque converter being engaged constantly is simulating lighting pushing the gas constantly, and is fighting and overpowering the e brake. It could be completely unrelated, but its my guess/assumption.

Any suggestions/ideas are welcome

 

@Taco critter

 

Only noticeable at idle though? Does the park vs drive issue make any sense from it being throttle related?

 

Could be a torque converter clutch issue, hard to say through the interwebs. I've seen valve bodies stick and cause the TCC to stall out motors at idle.

I would check fluid level of the trans first. Next step I would pull the pan after getting it red hot, do a full service and clean the screen.

The valve body solenoids can vary in prices dramatically, and are often hard to identify. So a fluid assault first would be good.

It could very well be the throttle body as well. Tough one.

 

I have this aswell, my advice is just clean the maf, throttle body, & iac valve and if that doesnt help just keep driving it till you get a check engine light, but dont throw parts at it

 

the first and least expensive thing I would check is does the brake light switch work and is it adjusted. This is an input to the PCM for brake lights, duh, AND torque convertor lockup operation.
The next thing I would check is the brake booster for proper operation/vacuum leak. I have seen a booster cause a higher than normal idle and low rough idle depending on the severity of the tear in the diaphram. The 4 cyl Tacomas are notorious for a low rough idle and as such, Toyota has changed the calibration for the idle rpms some 50 rpms greater in later PCM's. There have been other posts where the PCM's have been swapped in attemps to fix a low rough idle to no avail... trying to get Toyota to give out info as to what calibration level PCMs are the ones with the higher rpm has proven a waste of time.