Limp mode symptoms, without being in limp mode?? - Ford Powerstroke Diesel Forum
Powerstroke.org is the premier Diesel Truck Forum on the internet. Registered Users do not see the above ads.
Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 06-03-2011, 04:50 PM
Powerstroke.org Rookie
 

Join Date: Nov 2007
Posts: 14
Thanks: 0
Thanked 0 Times in 0 Posts
Feedback Score: 0 reviews
Limp mode symptoms, without being in limp mode??

I'm still having an intermittent problem with my 06 6.0. All stock, no modifications. There's been a few occassions while a very low speeds where my truck will all of the sudden drop to idle, and regardless if I mash the pedal to the floor, it will just idle. Usually within a minute or so, it will pick back up and respond normally. The limp-home wrench light has never come on, but it sure acts like it. Even at high speed, I've had it stumple a little. I've also had it where it wouldn't start. This is an intermittent problems that's driving me nuts. The only code I've ever gotten was a P0299 Turbo Underboost. I can't hardly believe the turbo (even with the vanes stuck) would keep it from starting. Maybe I don't know what I think I know .

I've did some recording here and there with AE, but can't put my finger on any problem. I plan to check the fuel pressure tomorrow, probably should have done that long ago.

Any suggestions.

Thanks,
Time2Live.
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2  
Old 06-03-2011, 04:57 PM
Powerstroke Techie

 

Join Date: May 2011
Location: Frederick MD.
Posts: 1,968
Thanks: 0
Thanked 8 Times in 8 Posts
Feedback Score: 0 reviews
That is weird. Internationals have that problem when they have a throttle pedal issue. You usually have to shut them off and cycle the key to get throttle back though. And they throw codes for that.

You're saying that if you just let it sit at idle it will finally rev up?
Reply With Quote Quick reply to this message
  #3  
Old 06-03-2011, 07:09 PM
Powerstroke.org Rookie
 

Join Date: Nov 2007
Posts: 14
Thanks: 0
Thanked 0 Times in 0 Posts
Feedback Score: 0 reviews
Yep, that's it. I'll even keep it to the floor, and suddenly it will slowly start going back to normal. I may have to also do some serious searching for some chafed wires tomorrow. It's really weird and the symptoms don't add up. Maybe that is whats going on. I even borrowed an oscope from work to check the cam and crank signals to make sure nothing is going on there. Many of the problems I think of should be covered by a code, but that may be assuming too much.

Any real insight or suggestions is appreciated.

Thanks again,
Time2Live

PS> Is there anywhere that really describes the control logic in great detail?? I even signed up for a 1 month subscription to the motorcraftservice.com for my vehicle. There's a lot of good information there, but to me it seems to lack a real detailed description of operation. Or maybe I'm not looking in the right place.
Reply With Quote Quick reply to this message
  #4  
Old 06-03-2011, 07:54 PM
Powerstroke Techie

 

Join Date: May 2011
Location: Frederick MD.
Posts: 1,968
Thanks: 0
Thanked 8 Times in 8 Posts
Feedback Score: 0 reviews
That is really weird. I would agree that it should have logged a code. Usually if something glitches like that for more then 10 seconds or so it will throw a code. I'd be curious to see what ICP pressures were doing when it did this.

What system/circuit are you looking for information on? I have acess to Internationals website which goes over most of the engine control information. Not sure if the Fords use the exact same throttle pedal setup. Most of the engine control stuff is the same though.

Really without a code or some way to narrow down what's glitching it's kind of a shot in the dark.....
Reply With Quote Quick reply to this message
  #5  
Old 06-03-2011, 08:02 PM
Powerstroke Techie

 

Join Date: May 2011
Location: Frederick MD.
Posts: 1,968
Thanks: 0
Thanked 8 Times in 8 Posts
Feedback Score: 0 reviews
Here's some of what I found on throttle pedal. Now this is for International so I don't know how much is relavent for you. I would think Fords are somewhat the same. The pinout numbers probably won't be the same. The symptoms you described sound like problems we have with the Internationals though. It's just weird because an International will throw a code right away for this, and the only way to get throttle back is to cycle the key. Here's what I have though.


The APS/IVS are integrated into one component and mounted on the pedal. The accelerator pedal assembly is serviceable to the extent that the APS/IVS switch can be replaced without replacing the complete assembly.

The ECM determines the accelerator pedal position by processing input signals from the APS and the IVS.

The accelerator pedal position is one of the controlling variables in the calculation of desired injection control pressure.

APS


The ECM sends a regulated 5V signal through the ECM chassis connector terminal X4-4 to APS connector terminal C. The APS then returns a variable voltage signal (depending on pedal position) from the APS connector terminal A to the ECM at terminal X4-18. The APS is grounded from connector terminal B to the ECM signal ground terminal X4-24.

APS Auto-Calibration


The ECM learns the lowest and highest pedal positions by reading and storing the minimum and maximum voltage levels from the APS. In this manner the ECM auto-calibrates the system to allow maximum pedal sensitivity. The ECM auto-calibrates as the key is on, but when the key is turned OFF, these values are lost. When the key is turned on again, this process starts over. When the pedal is disconnected (or a new one is installed), the pedal does not need to be calibrated. It simply auto-calibrates the new pedal assembly whenever the key is turned on again.

IVS


The ECM expects to receive one of two signals through the ECM chassis connector terminal X4-12 from APS/IVS connector terminal D:


0V when the pedal is at the idle position.
B+ when the pedal is depressed
The IVS receives a 12V ignition voltage at terminal F from the ignition fuse in the power distribution box. When the pedal is not in the idle position (throttle applied), the IVS supplies a 12V signal to the ECM.

The ECM compares APS/IVS inputs to verify when the pedal is in the idle position. If the APS signal at terminal X4-18 indicates throttle is being applied, the ECM expects to see 12V at the IVS. If the APS signal indicates throttle is not applied, the ECM expects to see 0V at the IVS. The timing process is critical between the APS and IVS sensors. For this reason, it is very difficult to determine if the APS/IVS assembly is working correctly when using a Digital Multimeter (DMM).

Fault Detection / Management


When the key is on, the ECM continuously monitors the APS/IVS circuits for expected voltages. It also compares the APS and IVS signals for conflict. If the signals are not what the ECM expects to see, DTCs will be set.

Any detected malfunction of the APS/IVS sensor circuit will illuminate the amber ENGINE lamp. If the ECM detects an APS signal Out of Range HIGH or LOW, the engine will ignore the APS signal and operate at low idle. If a disagreement in the state of IVS and APS is detected by the ECM and the ECM determines that it is an IVS fault, the ECM will only allow a maximum of 50% APS to be commanded. If the ECM cannot discern if it is an APS or IVS fault, the engine will be allowed to operate at low idle only.
Reply With Quote Quick reply to this message
  #6  
Old 06-03-2011, 08:39 PM
Powerstroke.org Rookie
 

Join Date: Nov 2007
Posts: 14
Thanks: 0
Thanked 0 Times in 0 Posts
Feedback Score: 0 reviews
justinmix, thanks so much for your replies. Yep, I believe they're very similar. Here's what I found regarding the APP:
Accelerator Pedal Position (APP) Sensor
The APP sensor is a 3-track potentiometer that is used to calculate driver demand for fuel quantity. The sensor receives a VREF voltage from the PCM and provides a variable voltage signal directly proportional to the accelerator pedal position.

A detected malfunction of the APP sensor illuminates the electronic throttle control (wrench) indicator. A PCM detected fault on one of the 3 sensor signals permits normal engine operation. A fault with 2 sensor signals only allows the engine to operate at idle.
It does say that a fault with 2 sensor signals will only allow the engine to idle, but it also says a detected malfunction will light the wrench, throwing it into limp mode. And my understanding is that once this happens, just as you mentioned, the key has to by cycled for it to clear if the conditions have cleared also.

This is a really odd problem. It's not always that it drops to idle and doesn't respond. It sometimes idles very low for a short time when coming to a stop. Sometimes a slight surge will accompany the low idle. I'm guessing it's just hunting for the correct idle.

Just for the heck of it, tomorrow I'll see if I can disconnect two of the three APP sensors to see if it will just idle, AND light the wrench indicator, and require a switch cycle to reset.

What's bothering me is I have a trip to Florida planned pretty soon, so I need to figure this out before then, so I can rest assured that I won't have to deal with this while on vacation.

I guess it could be worse. I could be less fortunate and not able to afford the beast, and not able to afford vacation.

Thanks again for your help. If I find something, I'll definitely update this thread.

Time2Live
Reply With Quote Quick reply to this message
  #7  
Old 06-03-2011, 09:00 PM
Powerstroke Techie

 

Join Date: May 2011
Location: Frederick MD.
Posts: 1,968
Thanks: 0
Thanked 8 Times in 8 Posts
Feedback Score: 0 reviews
Eh, I don't think you can unplug it one at a time. Those 3 different sensors are all self contained in the throttle pedal, if I'm not mistaken. The only thing you could do is unplug it, which i'm sure will cause it to default to idle.

I'd really be curious what ICP pressure is doing though. I think this is more of an ICP or fuel issue. ICP should throw codes though. So that leads back to fuel issue? There really isn't anything on these that moniters fuel pressure.

But if it was fuel pressure I'd think you'd really have some missing and cylinder balance codes going on with it.

I'm thinking ICP issues somewhere. Or the chaffed wiring. I'd look that over real good and try wiggling the wiring harness while it's running and see if you can't get it to glitch.

Sorry, I'm just rambling some different theories here. Not sure if I'm helping or hurting now!
Reply With Quote Quick reply to this message
  #8  
Old 06-05-2011, 04:59 PM
Powerstroke.org Rookie
 

Join Date: Nov 2007
Posts: 14
Thanks: 0
Thanked 0 Times in 0 Posts
Feedback Score: 0 reviews
justinmix, don't be sorry for rambling. Any discussion on the subject helps. Thanks for your replies.

So much for checking the fuel pressure this weekend. I didn't realize the fuel port fitting adapter would be that hard to find. I checked all the auto places around my neck of the woods and couldn't come up with one. I'll have to order one tonight. I just as soon order a decent test guage while ordering. Anyone have any suggestions for a decent set up to test the fuel pressure on a '06? Would be nice if the correct adapter (M12x1.5) would come with it, but I can order it separate if necessary.

Thanks,
Time2live
Reply With Quote Quick reply to this message
  #9  
Old 06-06-2011, 04:13 AM
Powerstroke Techie

 

Join Date: May 2011
Location: Frederick MD.
Posts: 1,968
Thanks: 0
Thanked 8 Times in 8 Posts
Feedback Score: 0 reviews
I got my fitting at a local hydraulic hose store. If you can find a place like that they should have the fitting that you need. I got a liquid filled gauge from there also. I originally used a Matco oil/trans pressure gauge set to check fuel pressure. The hose that came with that set was about 5' long which was nice so it would reach back into the cab. Most automotive fuel pressure gauges only have a very short hose on them. I like to be able to see what fuel pressures doing while driving so the longer hose is nice.

I'm sure if you could find a hyrdaulic hose store they could make you up a short hose also. Or just get the Mac or Matco oil/trans pressure gauge set. Even the fuel pressure guage sets from Mac or Matco have the short hose and are rather expensive.

As far as finding a gauge set with the fitting in it I have yet to find one. The problem is that most of your fuel pressure gauge sets are more designed for cars. So even with the fancier sets that come with alot of fittings won't have the one your looking for.
Reply With Quote Quick reply to this message
  #10  
Old 06-18-2011, 09:17 AM
Powerstroke.org Rookie
 

Join Date: Jun 2011
Posts: 6
Thanks: 0
Thanked 0 Times in 0 Posts
Feedback Score: 0 reviews
Same issue with my 06 6.0

I have the same issue as the OP.

Did you resolve your problem?
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Ford Powerstroke Diesel Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Display Modes

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -8. The time now is 04:38 PM.


Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Optimization by vBSEO 3.6.1
Garage Plus, Vendor Tools vBulletin Plugins by Drive Thru Online, Inc.

vB.Sponsors