2003 won't accelerate after sudden braking

[jbird]

After harsh/sudden braking '03 thunderbird won't "go" or rengage.
I reproduced this several times by:
1-harsh braking and stopping
2- harsh braking and then resuming my trajectory or turning.
In each scenario, I put my foot back on the accelerator, RPMs go up but the car won't go.
to resume my travel, I've tried:
1- Continuing to push gas, feathering it so I don't jolt, the car may then jump and then move forward.
2- shifting to P and then back to D5 or D4
3-shifting to manual and 1st or 2nd
4- shifting to P and then turning off engine, restarting engine
All of these attempts work, but it requires a small amount of time to pass... 1minute in most cases.
Facts: I've determined this has been an issue since I got it in May 2024
Has a new remanu tranny from June 2024
Thanks!!

This page contains affiliate links for which I may be compensated. As an eBay Partner, and Amazon Associate I may be compensated if you make a purchase at no cost to you.

 

[LAMBERTB]

My next stop would be back at the shop that did the transmission work.

 

[doug7740]

Here's your Monday puzzler. Thanks for reading.
After harsh/sudden braking '03 thunderbird won't "go" or rengage.
I reproduced this several times by:
1-harsh braking and stopping
2- harsh braking and then resuming my trajectory or turning.
In each scenario, I put my foot back on the accelerator, RPMs go up but the car won't go.
to resume my travel, I've tried:
1- Continuing to push gas, feathering it so I don't jolt, the car may then jump and then move forward.
2- shifting to P and then back to D5 or D4
3-shifting to manual and 1st or 2nd
4- shifting to P and then turning off engine, restarting engine
All of these attempts work, but it requires a small amount of time to pass... 1minute in most cases.
Facts: I've determined this has been an issue since I got it in May 2024
Has a new remanu tranny from June 2024
Thanks!!

Has anyone checked the automatic transmission fluid level? A low fluid level could be the cause.

doug7740
1955 Thunderbird Blue

 

[LAMBERTB]

My next best guess would be a problem with the ABS module.Have you check for codes with a OBD reader?

 

[Frankie the Fink]

Checking codes as a first step, then look at the transmission and any vacuum lines to the brake booster...
I

 

[jbird]

Been gathering data, I've narrowed the behavior down to when I am in d4.
Thanks for the input everyone.

 

[jbird]

My next best guess would be a problem with the ABS module.Have you check for codes with a OBD reader?

Also: I have checked for codes and haven't had any related to ABS since I had an alternator problem (it died) a few months ago.

 

[NickTbird]

I have the same issue, although mine re-engages a few seconds after I remove my foot from the brake. Short enough for my brain not to realize that this is the reason I am not accelerating and it slams into gear before I can remove my foot from the accelerator.

My transmission also has a slight buzzing noise, which didn't change after a fluid flush. I have believe could be fluid leaking internally around the shift pistons (which is a common issue with the transmissions, at least in the 2002, and good rebuild kits have the fix), but I haven't brought it to a transmission shop yet. Wasn't sure if it was related, but seeing as you didn't mention a buzzing noise, makes me think they aren't related.