RPM stutter during acceleration, 2004 Taurus

[04SE]

Vehicle is a 2004 Ford Taurus with 3.0 Vulcan (Car has 107,750 miles)

I have an interesting thing happening that is hard to describe. While accelerating under a normal load (idle to ~3,000) the car will increase in RPMs just fine until about ~2,600 RPMs then the needle on the tach will just fall down to 2,200 RPMs and hang there for 2-3 seconds and then continue to climb normally again. Meanwhile, the car never stutters or hesitates. There is a slight feeling of a loss of power, but barely. There is not an audible difference in engine sound or any other noises. It ONLY does it during this RPM range. Above or below this range it runs like a top.

I used my scanner on a few runs to check for codes and watch a few parameters live. The computer is pulling timing during this little event from ~18* to ~6* and then it shoots back up to ~18*. So something IS happening, I just do not know what is causing it.

The plugs have ~10,000 miles on them (Motorcraft OEM). The coil and wires are factory.

Should I spend the $120 and put a new coil and wires on or should I pay the dealer to put the screws to me? Nobody can understand what I am trying to explain here when I ask people about it.

 

[Frbl]

Perhaps a faulty Throttle Position Sensor? There are ways to test it - Google can lead you to those ways.

 

[chad8]

http://www.taurusclub.com/forum/index.php?s=a550ed964eb555660018411e9255ad6e&

Ask on this site. They are the tauri experts. I have a 2003 with the same motor. you typically need the mileage and other questions like when the gas filter was changed. It could be a number of things from a maf, tps, gas filter , or coils too.Even a bad injector could cause it.
Middle rpm ghosts are hard to find.
i would start with a good injector cleaner (Lucas or tectron),new gas and air filter as well as cleaning the throttle plate and maf sensor. If that does not help then take each coil off and inspect wires and coils for burns and cracks. Then have the tps electrically checked.
That is a good start before you pay tons of money for the same thing.

 

[punisher]

Well, the PCM pulls timing frequently, be it due to TPS, knock sensor inputs, or even during transmission shifting. View those inputs on the scanner when it happens and see if one of those is causing the PCM to pull timing.

Other stuff applies also. Ck fuel trims during the event and see if they go lean (fuel pressure or MAF concerns). Lean conditions cause flat spots in acceleration, as well as set off knock sensors (if equipped), and timing is pulled.

Interesting symptoms. I miss the shop sometimes.

 

[Boss302fan]

Transmission/Torque converter?

 

[turbochem]

Originally Posted By: Boss302fan
Transmission/Torque converter?


Sounds almost like the transmission is trying to go into lock-up (or shifting to a cruising gear) before you want it to.

 

[04SE]

Do transmission shops have computers to monitor the transmission and what it is doing? I might stop by and have it looked at.

 

[Boss302fan]

When was the last tranny fluid change done? If it has been a while, then I would consider a tranny fluid change...

 

[meep]

low rpm hesitation often points to plugs/wires. high rpm often points to starvation (fuel delivery). middle rpm is a PITA.

vac leaks, dirty maf sensor? lazy map sensor (more likely sense it's relied on for faster transitions), carbon buildup around valves or in cyls. this may require some poking around.

M

 

[ltslimjim]

Originally Posted By: turbochem
Originally Posted By: Boss302fan
Transmission/Torque converter?


Sounds almost like the transmission is trying to go into lock-up (or shifting to a cruising gear) before you want it to.


This is what happens on my Stratus, I've changed to ATF and added LubeGard red to try to help things. Definitely it is an issue of the torque converter going into lock-up/Overdrive with hesitation.

 

[04SE]

Originally Posted By: Boss302fan
When was the last tranny fluid change done? If it has been a while, then I would consider a tranny fluid change...


~80,000. It is due for one at 110,000. (It has 107,750)

Originally Posted By: meep
low rpm hesitation often points to plugs/wires. high rpm often points to starvation (fuel delivery). middle rpm is a PITA.

vac leaks, dirty maf sensor? lazy map sensor (more likely sense it's relied on for faster transitions), carbon buildup around valves or in cyls. this may require some poking around.

M


Will investigate further.

Originally Posted By: ltslimjim
Originally Posted By: turbochem
Originally Posted By: Boss302fan
Transmission/Torque converter?


Sounds almost like the transmission is trying to go into lock-up (or shifting to a cruising gear) before you want it to.


This is what happens on my Stratus, I've changed to ATF and added LubeGard red to try to help things. Definitely it is an issue of the torque converter going into lock-up/Overdrive with hesitation.


I do have torque converter shudder when the ambient temp is cold (

 

[mechtech2]

To eliminate the question of if it's lock up related, simply put it in a lower gear and see if it misbehaves.

 

[ltslimjim]

When I downshift manually using 3rd and L(load is 2nd gear), the transition to 2nd is sometimes rough and that's between 10-15 MPH. I should be slow enough already, but it acts like I threw it into 2nd at 30 or 40.

 

[1 SX]

I would change out the fluid an filter with a name brand, and see what happeneds. the transmission should shift pretty smooth. Also could be motor mounts/ transmission mounts allowing the engine play. How long does it take to downshift once you put the car in L or 3? If it takes any amount of time, then feels sloppy or loose as it engages, most likely it's over used fluid.

 

[meep]

I'm gonna say the ATF change here would be good too. If it's losing it's add-pack or thinning out too much, it could contribute to the slap-shift, or too grippy in partial TC lockup (if this AT does this, many others do).

M

 

[tangojetta]

That sounds like coilpack problem I had on my MPV with a duratec motor.