Limping Home

[Midlife]

A couple of weeks ago, I found the 2006 GT to be boggy and very responsive when letting off the gas, like there was significant backlash in the rear axle. I found the "wrench" light lit, so I pulled over, and found that the Mustang to be in "limp home" mode. I started up the car, and it disappeared. Just today, it did it again (almost in the same spot crossing the main bridge going back home), so I pulled over, turned the car off, and restarted it...the light stayed lit. I then turned the car off again, turned the A/C fan off, and opened the door. Closed the door, started up the car, and it ran fine.

OK...go back home, consult my FSM, and find nothing...everything is in the ECP manual which I don't have. Google seems to suggest a throttle body sensor or related problem, but nothing in my manuals for diagnosis or trouble-shooting.

I don't have a trouble-code reader either. Can anyone help me further?

 

[bigb427]

Throttle position sensor failures are some what common, it is most likely what your problem is. I would need to know what codes are in it unfortunately to know for sure.

 

[AzPete]

Auto Zone should be able to pull the codes......

 

[Midlife]

Update: it did it again today at the same spot! After leaving work I cross a bridge, and come to two lights. I have the AC on max, and after crossing the bridge turn it to outside air. At the second light, I had to wait a full cycle. I pulled out in first, and shifted to second before really getting up to speed and *wham!* it went into limp mode. I pulled off, cycled the engine power, and everything was A-OK. Went to autozone, and had them read codes: all clean. They said to go to Ford, so I did...they read codes: all clean. The tech said I have to drive it in in limp home mode for them to do diagnosis.

Now I did notice some corrosion on the negative battery terminal that wasn't there last Thursday...hmmm....Ford wants $85 for a new cable harness so I ordered it. I could put on a new terminal, but my experience with non-crimp battery terminals is horrible.

 

[bigb427]

Sounds just like a TP sensor going bad. Unfortunately the fault isn't present long enough to set a code. If you can leave it with the dealer, they should be able to confirm the concern as these do go bad fairly often.

 

[scedd]

dont go home that way anymore!

 

[Midlife]

dont go home that way anymore!

There's only one way home from work. After constructing a new bridge, they shut the old one down so they could blast it with dynamite. Traffic was backed up to kingdom come, and I had to catch a plane on the other side of the bridge. I barely made my flight.

Update: bought a Motorcraft TPS from the Ford stealership, and the parts guy told me all about these problems. There was a TSB in 2005, but apparently the problem still occurred in 2006. The part looks nothing like the original. The FSM says not to use any cleaner on the throttle body (say what?), and it appears Ford used some sort of chemical protectant to stop fouling of the TB. I asked the parts guy about it and he said just keep it away from the TB motor itself...don't spray it but wipe it with a cloth.

 

[bigb427]

You'll want to use a heat gun or a mini torch on the screws that hold the throttle position sensor on. Get them good and hot because they were locktited on. The screws are very easy to break off so apply more heat if they are not un-threading easy.

 

[Midlife]

Yup...the instructions say that. I have a heat gun and a thermal sensor as well! I'll have AZPete at the ready with appropriate fire-suppression materials (e.g. beer).

 

[Midlife]

Update: replaced the TPS, one of the easiest jobs on these complex beasts. Took the throttle body off, cleaned it up (it wasn't too dirty), and stuck it back on. We did heat up the TB to loosen up the locktite on the TPS bolts and still managed to break one bolt off. We finally got it out, though.

Went for a quick drive and the car seemed a bit more responsive. I'll be monitoring the car closely for a couple of weeks.