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13 SPI: Bad PTU or torque converter?

Started by Alex Fiorelli, January 27, 2022, 09:23:38 PM

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Alex Fiorelli

Hey guys, just picked up a 13 Taurus PI with the 3.5 Eco, 79k miles. Day 1, I immediately noticed a rough idle but didn't think anything of it. The 2nd day is when I drove it to and from work. On the way home (30 min each way), I was cruising uphill about 40mph at low RPM (1500) and noticed surging and rough acceleration. Once the RPMs climbed above 2K, or when I pressed the gas hard, it smoothed out - until I slowed down and started cruising again. The next day I noticed the issue got worse once the car warmed up, meaning at colder temps, the shuddering wasn't as bad, but it gets pretty bad at operating temps and when the RPM is below 2K.

I took it to a shop who confirmed it had nothing to do with spark, air, or fuel. I even supplied fresh coils and plugs, which I wanted to do anyways. They noticed the PTU was leaking (and a broken motor mount) so they distilled the problem down to the PTU and/or torque converter. The dealership I purchased this car from (located out of state) offered to pay $1,500 for a new PTU, but I'm still looking at a hefty bill if I decide to get both done.

Here are my question and other observations as I'd like to start by replacing just the PTU first:
1. Could a bad PTU make your idle rough and fluctuate when not moving, say 50RPM up an down?
2. Could a bad PTU cause this surging and rough acceleration? (there is a slight grinding sound from the drivetrain)
3. When mashing the gas, the gears shift just fine - would a bad torque converter make every gear gift rough?

Basically I'm asking what exactly may support it being just a bad PTU as I don't exactly mind replacing that, flushing the transmission, and seeing if that fixes the issue.

Is there something definite that points to either PTU or TC? If the PTU is leaking, would that be an obvious culprit?

Thank you!


TopherSho

Rough idle and the over revving makes me think of the speed sensor on the tranny. Especially with the reving not going wild when you apply MORE torque at higher rpms.. It has been seen here in these forums to have non-coding weird effects on idle, and rpm divergence at flat cruise control speeds.


The broken motor mount is a red flag to me .. that needs looked at.  if it has been ''sheered off'' this car has been super abused and i'd consider sending it back.. If this was not from a police auction it may have been previously tuned and ran without torque reduction on the 1-2 shift which is *brutal* (mega hard wheel hop) and shocks the hell out of the powertrain ..  If the rubber ''just fell apart'' and is kinda crumbly that's just age in a really dry environment.

PTU leaking .. if the motor mount just ''dried up and separated'' then the ptu seals may have become too dry.  Maybe it sat in a yard for a few years and dried out.  However .. since it is missing fluid you need new fluid in it asap.  If it keeps leaking you need a new ptu.  Get a new used one from a 2015 or newer wreck.. look for UNDER 40k miles if possible.  If you cannot find one under 60k miles pony up and buy a new one ..

torque converter .. uffda~  diagnose the 'speed sensor first' .. it is cheap,  and you can get to it with tall safe ramps (no harbor freight :D  ) .. if after replacing the speed sensor and inspecting  sensor harness the revs still waver Id try as a experiment drain out 1/2 quart tranny fluid and drop in your trusted brand of trans fluid treatment to aid with slippage.  if it gets better with the sticker fluid then change the fluid 100% and see if just new fluid helps .. if after that it is still wavering ... you need a new TQ





2010 non-pp, 98k miles, 3-bar,  .026 plugs, SNOW-KIT STG1, AJPTurbu tune#35, 15.5+psi
Best 0-60 public road 4.35s
Best 1/4 of 12.61 no DA correction

Alex Fiorelli

Quote from: TopherSho on February 01, 2022, 04:15:05 PM
Rough idle and the over revving makes me think of the speed sensor on the tranny. Especially with the reving not going wild when you apply MORE torque at higher rpms.. It has been seen here in these forums to have non-coding weird effects on idle, and rpm divergence at flat cruise control speeds.


The broken motor mount is a red flag to me .. that needs looked at.  if it has been ''sheered off'' this car has been super abused and i'd consider sending it back.. If this was not from a police auction it may have been previously tuned and ran without torque reduction on the 1-2 shift which is *brutal* (mega hard wheel hop) and shocks the hell out of the powertrain ..  If the rubber ''just fell apart'' and is kinda crumbly that's just age in a really dry environment.

PTU leaking .. if the motor mount just ''dried up and separated'' then the ptu seals may have become too dry.  Maybe it sat in a yard for a few years and dried out.  However .. since it is missing fluid you need new fluid in it asap.  If it keeps leaking you need a new ptu.  Get a new used one from a 2015 or newer wreck.. look for UNDER 40k miles if possible.  If you cannot find one under 60k miles pony up and buy a new one ..

torque converter .. uffda~  diagnose the 'speed sensor first' .. it is cheap,  and you can get to it with tall safe ramps (no harbor freight :D  ) .. if after replacing the speed sensor and inspecting  sensor harness the revs still waver Id try as a experiment drain out 1/2 quart tranny fluid and drop in your trusted brand of trans fluid treatment to aid with slippage.  if it gets better with the sticker fluid then change the fluid 100% and see if just new fluid helps .. if after that it is still wavering ... you need a new TQ

Thank you for the reply! The car was from a police auction and the dealer is covering the PTU and motor mount replacement. It wasn't sheared, just had a lot of play. The PTU I purchased brand new so it has a drain plug which means I can service the thing every 20-30k.

If the vehicle still has a slightly uneasy idle and issues at low RPM high load, I'll replace the VSS and take it from there.

Will report back. Thanks again!

Alex Fiorelli

Quote from: Alex Fiorelli on February 01, 2022, 09:54:15 PM
Quote from: TopherSho on February 01, 2022, 04:15:05 PM
Rough idle and the over revving makes me think of the speed sensor on the tranny. Especially with the reving not going wild when you apply MORE torque at higher rpms.. It has been seen here in these forums to have non-coding weird effects on idle, and rpm divergence at flat cruise control speeds.


The broken motor mount is a red flag to me .. that needs looked at.  if it has been ''sheered off'' this car has been super abused and i'd consider sending it back.. If this was not from a police auction it may have been previously tuned and ran without torque reduction on the 1-2 shift which is *brutal* (mega hard wheel hop) and shocks the hell out of the powertrain ..  If the rubber ''just fell apart'' and is kinda crumbly that's just age in a really dry environment.

PTU leaking .. if the motor mount just ''dried up and separated'' then the ptu seals may have become too dry.  Maybe it sat in a yard for a few years and dried out.  However .. since it is missing fluid you need new fluid in it asap.  If it keeps leaking you need a new ptu.  Get a new used one from a 2015 or newer wreck.. look for UNDER 40k miles if possible.  If you cannot find one under 60k miles pony up and buy a new one ..

torque converter .. uffda~  diagnose the 'speed sensor first' .. it is cheap,  and you can get to it with tall safe ramps (no harbor freight :D  ) .. if after replacing the speed sensor and inspecting  sensor harness the revs still waver Id try as a experiment drain out 1/2 quart tranny fluid and drop in your trusted brand of trans fluid treatment to aid with slippage.  if it gets better with the sticker fluid then change the fluid 100% and see if just new fluid helps .. if after that it is still wavering ... you need a new TQ

Thank you for the reply! The car was from a police auction and the dealer is covering the PTU and motor mount replacement. It wasn't sheared, just had a lot of play. The PTU I purchased brand new so it has a drain plug which means I can service the thing every 20-30k.

If the vehicle still has a slightly uneasy idle and issues at low RPM high load, I'll replace the VSS and take it from there.

Will report back. Thanks again!

Following up with some good news - the new PTU and transmission flush completely addressed the issue. I guess a PTU that is binding up affects engine load and RPM - who knew!

She runs like a champ now, plus I can service the newer style PTU (along with the transmission) every 20-30k to extend life.

Macgyver


TopherSho

Awesome!  Dont forget the RDU ..

https://www.ecoboostperformanceforum.com/index.php?topic=1708.0

Also as someone who personally lost an engine to rear bank injector failure .. figure out a time to pull and test the injectors if your serious about keeping it for a long time tuned ...




2010 non-pp, 98k miles, 3-bar,  .026 plugs, SNOW-KIT STG1, AJPTurbu tune#35, 15.5+psi
Best 0-60 public road 4.35s
Best 1/4 of 12.61 no DA correction