Transmission Slip/Low Idle after hard stop

[BigMike18]

Coming home from work today I was going about 70-80 mph when traffic suddenly slowed to a stop only in my lane. Some cars had to move to shoulder to avoid collision, but wasnt the hardest stop I've experienced, no tires were screeched or curse words were said.

Following that once the flow started moving again, my 05 v8 struggled to get up to speed and my normal pedal pressure was not working and it chugged along. At about 35 I had a burst of power and was back to normal acceleration it felt like. Still I knew something was wrong, as traffic continued I noticed a rather low drive idle at a stop 500-550 rpms at around 180-190F Coolant temp. (I checked when I got home my park idle was 700-750 at same temp). I felt like the car was soon going to stall out. This stop and go continued and 0-10 felt normal and from 10 to about 35ish was sluggish and I felt like I had no control over speed. I was able to get up to 70 again like normal but still had the same issue once off the highway and back down to slower speeds.

I have a few ideas swirling in my head over what this could be, but wanted to get on the forums and see if anyone had heard of or experienced something similar.

 

[Hungryhawk]

It could be more than one issue.
So I would begin by simple cheap stuff. Buy or borrow a OBD2 code reader. I had a cheap one that output to android cell phone and it solved problems with lots of vehicles. Now I have a more capable Scanguage 2.
So review age of your sparkplugs, last cleaning of Mass Air Flow sensor, replacement of PCV valve. Upgrade these if indicated.
A good OBD2 reader can reveal fuel flow issues as you can get real time readings as you drive.
Deeper explorations will take a lot of your time and learning what and how to test systems.
If this needs to be your daily driver you are disadvantaged but you might get lucky and find a fix with above service.

 

[SocalSam]

Second on making sure tune-up items are in good order. Stumbling and hesitating can sometimes be interpreted as transmission slip so it could be an easy fix. A previous car would stumble at certain speeds which I thought was failing torque converter. It turned out to be an ignition coil with corrosion inside the boot. This never tripped a CEL. I should have gotten a scanner and checked misfire counts.

 

[BigMike18]

So I assessed the short and long term fuel trims and were all within 5% (one set was within 1% cant remember whether short or long) directly after this fiasco while I was parked, same day. I then dug around a bit online, youtube, and the forums and ultimately decided to do a drain and fill of the transmission. I waited about 1.5 hr to cool off a bit and then drained about 2 qts of dark brown reddish ATF from the vehicle. Then pumped in the same amount through the fill hole. I have previously done this once beforehand in the last year. I shifted through the gears and then once warm I took it for a spin and idle was back to normal, shifting of the gears was normal, and power/acceleration went back to normal. Highway speeds this morning on the way to work were good as well as the way back.

I did have the thought while at work that my sparkplugs are 5 years old and about 40,000 miles ago (Very fortunate my work and school commutes have been very short the last few years). Exhaust does have a slight leak between the cat and the header (working on that), nothing to trip a code though. Attached is a photo of the state of ATF fluid I pulled out of the car.

Local Toyota place to me said to do a full filter, gasket, and atf drain (not full flush) in the near future since the vehicle hasnt had one since before 200,000, if ever.

This is where im at with the vehicle, feedback would be appreciated and thank you for the suggestions before hand! Is there anything else metric wise I should check with the scanner?

 

[VortepJ]

So I assessed the short and long term fuel trims and were all within 5% (one set was within 1% cant remember whether short or long) directly after this fiasco while I was parked, same day. I then dug around a bit online, youtube, and the forums and ultimately decided to do a drain and fill of the transmission. I waited about 1.5 hr to cool off a bit and then drained about 2 qts of dark brown reddish ATF from the vehicle. Then pumped in the same amount through the fill hole. I have previously done this once beforehand in the last year. I shifted through the gears and then once warm I took it for a spin and idle was back to normal, shifting of the gears was normal, and power/acceleration went back to normal. Highway speeds this morning on the way to work were good as well as the way back.

I did have the thought while at work that my sparkplugs are 5 years old and about 40,000 miles ago (Very fortunate my work and school commutes have been very short the last few years). Exhaust does have a slight leak between the cat and the header (working on that), nothing to trip a code though. Attached is a photo of the state of ATF fluid I pulled out of the car.

Local Toyota place to me said to do a full filter, gasket, and atf drain (not full flush) in the near future since the vehicle hasnt had one since before 200,000, if ever.

This is where im at with the vehicle, feedback would be appreciated and thank you for the suggestions before hand! Is there anything else metric wise I should check with the scanner?

Some scanners can see the difference between the crankshaft speed and transmission speed, to show if you torque converter is shuttering. Your fluid does look a little dark, did you strain it through a paper towel looking for debris? If it's full of clutch material, most people will say don't touch it, but if it's clean then you could probably (important to remember) gain from a full filter and refill. There's always some risk with old transmissions.

Honestly if it was mine and everything was working currently, I'd wait to do the full flush until I see how things go for 2-3000 miles.