Hesitation issue-2008 Ford Mustang GT

[my1st66mustang]

Hello, I am currently having an issue where my car will hesitate massively when accelerating from a stop, I'll press the gas pedal and it won't engage for roughly 5-10 seconds. It is also common for the car to roll backwards on small inclines. This was moderately common when I first purchased the vehicle (knew about the issue before purchase) and I purchased another transmission that had 69,000 miles on it. The new transmission made it worse, now every acceleration from a stop results in the car hesitating. Please help me if you can, I thought that it was a transmission issue and don't want to go around in circles draining my bank account with parts that won't fix it. Any help is appreciated, Thank you.

Car specs:
-Car mileage: 160,000 miles
-New transmission milage: 69,000 miles
-Transmission Type: Automatic

 

[stkjock]

does the RPM of the engine move higher with application of the gas pedal?

when you say "engage" do you mean the transmission?

also what year is the car?

 

[my1st66mustang]

The RPM does move higher with the application of the gas pedal, it seemed like it was the transmission as the engine seems to be running fine, its a 2008. Thank you.

 

[stkjock]

sounds like transmission for sure then, either the converter or 1st gear is shot.

The 5r55s is not the strongest of transmissions

 

[my1st66mustang]

I replaced the transmission with one that had 69,000 miles on it from a dismantler and that should've fixed the issue and instead made it worse, so I would hope that replacing the transmission would've solved the issue. Could it possibly be a bad tune?

 

[07gts197]

Could just be low on fluid.


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[my1st66mustang]

Unfortunately we tried that too, the torque converter was full of transmission fluid. We tried pumping more transmission fluid into it and it started leaking back out so its full of fluid.

 

[07gts197]

The torque converter can have fluid while the pan is low. Im not very versed in the 5r but I do know they dont have a dip stick. Im sure 5r experts will chime in but draining the pan and torque converter is the only way of checking unless the fill hole can be used as an indicator of where the fluid level is.


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[my1st66mustang]

I screwed a shrader valve into the transmission bolt and pumped transmission fluid in and fuild came out after unscrewing the shrader valve which means that it is full.

 

[07gts197]

Could also be the range sensor


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[my1st66mustang]

We actually replaced that plug after it broke so that shouldn't be the issue

It broke during removal of the transmission so it wasn't broken before

 

[Steve Waters]

Are you sure the trans is actually in first gear and not second or a higher gear when pulling out from a stop? Any higher gear would possibly allow it to roll backwards because there isn't enough torque transfer so it would feel really slow and sluggish. That could be a computer or eleclrtical issue.

 

[my1st66mustang]

I don't know how to really tell what gear I'm in, is there anyway to see if theres an electrical issue through the OBD2 system

 

[Steve Waters]

I'm not real sure. My 06 is a manual. I would think a scan tool or a programer that can data log would show gear selection. My be worth starting a new thread on transmission electronics and or wiring. There hast to be a way to tell. The OBD2 port would be my guess too.

 

[07gts197]

You can datalog with an elm 327 scanner and use forscan lite to datalog trans pids among other things. Id suggest that before writing it off as a mechanical issue.


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[my1st66mustang]

Okay, I'll try that and I'm thinking that the best course of action if that doesn't produce anything is to take the old transmission to a place that has a transmission dyno to narrow the search for the problem down to only the transmission and if the transmission passes testing then I can look elsewhere for the issue.

 

[my1st66mustang]

07gts197, what parameters do I need to record and I've done a recording with some parameters that apply to the transmission and can export it to an .fsl or .csv file, would it be helpful to post either of those files here?

 

[07gts197]

Rpm, tcc, torque converter slip actual, oss, vehicle speed, gear commanded, throttle position actual, tps voltage. There are others but this will knock out a lot. If you can save it post it here or send it via email.


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[my1st66mustang]

I turned out that there wasn't enough transmission fluid in it as I talked with the dismantler and they said that they drained it all and we only put 5 quarts in it, thank you for helping me anyways.

 

[07gts197]

Kinda what I figured but Im glad you got it squared away!


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