Well Ladies & Gents,

This has happened twice in the last ten starting sequences. Everything is normal when starting the truck, however once I put it in drive and push on the go pedal nothing happens; the truck stays in idle. This phenomenon seems to only happen on the first start of the day.

The first time it happened I tried all forward gear options with no change. I shut it off and immediately re-started her up. Worked like a charm and off I went.

The second time (this morning and first start), same thing, started up just fine but didn't want to go anywhere. I cycled through ALL the gears and different chip settings on my DP tuner, and this time I discovered the pedal worked in Park & Neutral only. Shut it down and re-started, and just as before, off we went.

Any ideas what could be causing this? I have approximately 89,000 miles on her and if you read my thread about my recent front end problem & solution then you'd know about the stall or drastic hesitation I felt at highway speed while breaking in my new rotors & pads. This only happened once; could they be related? Thanks.

BTW, I searched for related problem but I don't believe it's my pedal switch.....but I've been wrong before, more than I care to count!

Recent mods this summer: BTS, DP Tuner, ATS housing, Spearco CAC, EBPV Delete. Oct 08 mods, AIS Foam sleeve (man does this work), Dieselsite coolant filtration sys & 203 thermostat, and the Dynatrac Free Spin kit with Dynatrac locking hubs (capped off the vacuum lines at the wheel well junction. I have my original CPS which has never given me any trouble.

 

If your PCM (Powertrain Control Module) doesn't see the presence of signal from your Idle Validation Switch (IVS) at startup, your pedal will be inop until it does. That signal only appears when the pedal is completely UN-depressed.

Try the following:

Before you try to start the truck, push down on the accelerator pedal and hold it down. Now, start the truck.

Notice it just starts and idles? Now release the pedal, but only part way, and push it back down to the floor. Nothing happens.

Now, release the pedal all the way up. The pedal should become active, because the PCM has now "seen" the IVS signal.

The switch gets "sticky". It's a microswitch that COULD be replaced, but you'll likely be just as successful simply spraying it well with contact cleaner.

The entire pedal assembly comes out for cleaning by removing an electrical connector and the three nuts that hold it to the floor.

That's what I'd try first.

Pop

 

Mine had some of the same symptoms. I would hit the throttle pedal to go, and nothing would happen. But I never had to shut the truck off. After a few seconds it would start working again.

Have you seen a check engine light? I didn't the first few times this happened, and then one day it happened again and the CEL came on, so I had it scanned. The scan showed that the throttle position sensor on the pedal was bad, so I replaced the pedal assembly (the only way the sensor can be replaced) and it has worked fine. This was this past summer.

If you have a scan tool or some way of getting it scanned, you may want to try that and see if it comes up with anything.

 

My truck has done this to me a few times, but it hasn't gotten serious enough to look into yet...subscribing so that I will know in the future

 

I had the same thing. Even going down the freeway at 60 it decided to cut out going up a hill and had a big rig riding my ***. A few seconds later it kicked back in and I was able to get back up to speed. I also had a slight shudder around 30mph where it felt like it lost a lot of power and not just go to idle, then it would kick back in. Also happened right after startup a few times. Got a SES light but I forget the code. Took it in under warranty and they replaced the pedal assembly because of the throttle position sensor. Hasn't happened since.

 

The Throttle Position Sensor (TPS) is nothing more than a potentiometer, and sends a varying voltage back to the PCM from it's reference voltage. If it goes open or intermittent (remember noisy "volume controls" in your radios?) then the PCM only knows to do what it's told.

Though I haven't measured the voltages involved, I would suspect zero (or minimum) volts would be idle, with maximum being "wide open", so it would be kind of fail-safe.

We wouldn't want an open sensor causing maximum acceleration, now, would we?

Pop

 

My little "switch" or whatever you want to call it that makes contact was actually bent. Unbolt the pedal, disconnect the plug and take a look. All I had to do was bend it back and I was on my way again!

 

I beg to differ Jeff. You can just replace the throttle position sensor and not have to shell out the money for the whole pedal assembly. The TPS is $59 by itself, and the whole pedal assembly is considerably more (List is $330).

Click here

 

Didn't realize our throttles were electric, learning every day!
(ps.USAF CCF, I recognize that patch, crewed the -135).

 

I beg to differ with you, Jason, but only in regards to the price for the sensor. (Sorry... couldn't resist following your example). I just ordered my TPS sensor from Y2K Ford Parts (site sponsor) for only $36 plus S&H.

Here's the link. http://www.trademotion.com/partlocat...=10&model=F250

Just enter "throttle" in the ley word search, and the top item is the TPS sensor.

 

Thanks Pop,

The trouble is I don't touch the pedal to start my truck. Yet when this symptom comes along, the pedal does work in Park & Neutral. However, when I put it in any go gear (forward or reverse) nothing happens but idle rpms. Both times after shutting down and restarting, no problem. I've never had a CEL, knock-on-wood! I don't think the IVS is the problem because of the characteristics of the problem. Still trouble shooting. Les

 

Thanks for serving, and taking great care of us "crew dogs"! Love the quote! V/r Les

 

I didn't know that the sensor could be had by itself, oh well. I sure know that the pedal assembly was not $330. We get a price discount at the shop, but I don't remember the exact price.