[yingjai]

I just want to have an idea of what the problem might be and possibly a ballpark on how much it's going to cost me before I bring it to the dealer.

It started a while ago but notice it more recently. I don't always floor the gas pedal, but noticed this problem on the highway. I can be going at 80km/h in 4th gear and if I floor the gas pedal (like going up a steep highway hill), the rev goes up seemingly like normal and suddenly dips down a little before going back up. It can happen in 5th gear, too. Today, I was using the cruise control and I was at 100km/h in 5th gear, I tried to resume to 110km/h and the same thing happened. The rev dipped down, but before it went back up, the cruise control disengaged.

I rarely floor it on 3rd gear, but I haven't really noticed this happening up to 3rd. If I'm more gradual with the gas pedal, this doesn't seem to happen.

 

[marylandGT]

First thing I'd do before I take it anywhere for a huge bill is change the fuel filter, unless you've done it already. Also run some good injector cleaner through it. Personally, I let it get down to almost empty then add the cleaner so it's not too diluted. I'll do this on a Friday and run it now and then during the weekend. Let it soak in those injectors for a couple days. Also, how old are the spark plugs? Maybe pull the plugs and have a look at them. These are all cheap and easy things I'd try before I let a dealer get their hands on it and my wallet. Haha. By the way, good luck and welcome to AFM.

 

[yingjai]

I bought this Mustang used about 2 or 3 years ago. I live in Canada and apparently it went all over the states until it got imported here.

Therefore I have no idea how old the spark plugs are.

 

[yingjai]

I haven't changed the fuel filter yet, but I did bring it to a Ford dealer and they couldn't find anything. We went for a test drive and the problem wouldn't show up.

I plugged in an OBD adapter and connected it to Torque on my phone. There were no fault codes, but some sensors failed the tests. I was wondering if this is helpful.

Mode $06 report generated by Torque for Android
================================================

Test report:
------------------
MID:$03 TID:$81
- O2 Bank 1 Sensor 3
Max: 3A Min: 0.22A
Test result value: 0A
FAIL
----
MID:$07 TID:$81
- O2 Bank 2 Sensor 3
Max: 3A Min: 0.22A
Test result value: 0A
FAIL
----
MID:$31 TID:$0a
Sensor period(calculated) - EGR Monitor Bank 1
Max: 57,417 Min: 22,544
Test result value: 65,520
FAIL
----
MID:$31 TID:$80
- EGR Monitor Bank 1
Test incomplete or dependant test failed
--
MID:$31 TID:$81
- EGR Monitor Bank 1
Test incomplete or dependant test failed
--
MID:$3a TID:$80
- EVAP Monitor (cap off)
Test incomplete or dependant test failed
--
MID:$3a TID:$81
- EVAP Monitor (cap off)
Test incomplete or dependant test failed
--
MID:$3a TID:$82
- EVAP Monitor (cap off)
Test incomplete or dependant test failed
--
MID:$7e TID:$37
-
Max: 57,074 Min: 10,319
Test result value: 65,523
FAIL
----
MID:$81 TID:$0a
Sensor period(calculated) - Fuel System Monitor Bank 1
Max: 57,416 Min: 6,160
Test result value: 65,520
FAIL
----
MID:$9e TID:$37
-
Max: 57,084 Min: 10,319
Test result value: 65,523
FAIL
----
MID:$b1 TID:$0a
Sensor period(calculated) -
Max: 57,418 Min: 6,160
Test result value: 65,520
FAIL
----
MID:$e1 TID:$0a
Sensor period(calculated) -
Max: 57,415 Min: 22,544
Test result value: 65,520
FAIL
----
MID:$f0 TID:$1d
Manufacturer defined MID -
Max: 0ms Min: 0ms
Test result value: 48,000ms
FAIL
----


End of report.

 

[az.dsrt]

How many miles on it? Sounds like a slipping clutch. Slipping usually starts showing it's self in the higher gears. It'll slip for a while, then catch, bringing the RPM's back down.

 

[yingjai]

Around 112k mi. Recently, I went up a hill and held the accelerator down in 5th and the tach revved up and down a few times. Last night on a flat stretch of highway, it revved up to 3k rpm, held there for a while, then continued to like 4-5k rpm before I quickly let go of the accelerator. I had Torque log too much too quick, so I was unable to get any data other than the sensor fails.

 

[az.dsrt]

I have Torque, cool tool. The fails you see are due to the reading being outside of the min-max value. The min-max value is pretty much a guess on Torque's part, you can adjust those values if you know what they should be. Regardless, I don't think Torque is going to give you any info on a slipping clutch, which is pretty much what you are describing. Also, at 112k miles, that's a long ways for a clutch to last..

 

[yingjai]

I was trying to record:

• Transmission Gear
• Engine RPM
• Speed (OBD)
• Engine Load
• Accelerator Position
• Throttle Position (Actual)
• Throttle Position (Desired)
• Engine Coolant Temperature

None of that would've helped?


I've never noticed this problem in 1st gear. Not sure about 2nd, but definitely 3rd to 5th and only if I put my foot down really quick.