Limp Home Mode

[MercedesTech]

:sniffle:

Was playing with customizing my tunes yesterday after work (stock tunes, waiting for Bill's custom tunes). I was using #3 performance tune. I changed tire size to try and dial in my speedo, I adjusted WOT shifting, but not by much. I am around 5100 on the 1-2 shift and a little less on the 2-3 shift. I then bumped up my timing to "1". I programmed it, went to drive off to see how it feels. Made it 100 yards with no issue. Then "pop" and instant loss of power. Engine stayed running, the wrench came on, and I was in "limp home mode". I then stopped, went back into the gryphon and reset previous (befre these changes) settings. Loaded those and was good to go.

What I'd like to know, was it my timing bump ? How much does each .25 actually advance the timing ? What would be a safe timing bump ? if any.
My truck is a 2004 Ford F150 4x4 w/ 4.6 L motor. I have a Fabtech 6" lift, 35" M/T tires. No other real drivetrain mods. I only run Chevron 91 octane (highest octane out this way).

Thanks for any info.

[Jackpine]

I'm not the expert here, Bill is. But, I'll offer my thoughts.

Level 3 already has advanced timing to run 91+ octane gas. I think your advance of 1 point (and sorry, I don't know if this is really degrees) was WAY too big. The manual suggests a 0.5 increase for each octane number increase, so your timing was set up to the 93 octane level.

I'm surprised that put you into limp home mode, especially so quickly, but I can't think of any reason for the other changes to cause the problem.

I know I tried advancing the timing by 0.25 once (since we live at 2500 feet, and you should be able to advance the timing some for increased altitude) and it caused my idle to "wander". (I've said I advanced it 0.5 in other threads, but that was because I couldn't remember the smallest possible adjustment increment - which is what I actually tried). So anyway, I think the truck is VERY sensitive to timing issues, and that's where I'd put my money. Be interesting to hear what Bill thinks.

- Jack

[Power Hungry]

Mercedes,

The timing changes are in actual degrees, so +.25 is actually adding ¼ degree of timing advance. I doubt the timing really had anything to do with it, although if it did it is more the possibility that the engine is making more power than expected and the computer is not happy.

Did you happen to have a second to check the DTCs? I have been hunting down a couple problems with a P061B DTC that has to do with a problem with torque calculation. I have 1 or 2 other customers that have had a similar issue. It doesn't occur all the time but it usually happens right after reprogramming the vehicle to a level.

When it does occur, you don't need to reprogram back to stock. All you should have to do is...

• Turn the key off
• Turn the key back on (Don't start)
• Go to the Diagnostics menu
• Clear the DTCs
• Turn the key off
• Restart the truck

It shouldn't occur again.

As I said, there is something in the torque calculation that is causing the issue and I'm working with a couple folks to get the issue isolated and resolved. As soon as I come up with a final solution, we'll be able to do a calibration update.

Stay tuned...

[MercedesTech]

Thanks Bill ! I was hoping you would chime in for me. I didn't think "1.0" = 1* of timing. I don't know why, but I thought it would be less. I still don't fully understand how it would cause the limp home mode, but I'm not a Ford tech, so ??? I didn't go back to stock, just went to level 2, and already had custom tunes I had used, and knew worked. I programmed that with the gryphon into the truck, and was good to go.

I have yet to pull the DTC's. I was on my way to pick up a customer car, so was in a bit of a hurry. Truck has been sitting since. I figure I have time tonight, I'll tinker with it a little bit. If I pull a code, I will be sure to post it up, so you can see which one.

So, with my truck, running 91 octane, you think I should leave it alone ? I have bumped it up to .25 or .50 before without issue. Might try .75 and see. Any suggestions ? Might just play with it to see what happens.

Can't thank you enough for the reply ! You rock !
- James

[Jackpine]

And I learned quite a bit here too! Thanks to both of you! I DO know, James, that the "standard" advice is to make changes VERY gradually and do them one at a time to prevent confusing interactions. So, if I were trying to advance the timing again, I'd probably try 0.25 degree increments.

- Jack

[Sburn]

I had this happen yesterday after adjusting canned tune #2, 87 towing. To help Bill track this one down, here's the info:

2007 4.6

Had been running #2 tune for a few days with no custom changes and no issues. I then made a couple of changes from the base program:

Idle speed +75 (this seems to help driveability in parking lots)
WOT enrich 1.3 -> 1.5

Gear ratio from 3.73 -> 3.55

The canned tunes all seem to default to 3.73 even though my truck has a 3.55 (axle code 19 on the door sticker).

Tire size from 237X to 2337. Like gear ratio, canned tunes seem to start with very slightly incorrect values.

Not from a full cold start -- off for about three hours, but mostly warmed up (~160 degrees CHT). Taking off from a stoplilght, about 1/3 throttle, ETC light and loss of power hit right around 1-2 upshift. No CEL light.

Limped a few blocks to a parking lot, shut off. Key on, diagnostics, DTC P061B only. Returned to stock. Hit the drivethrough and back to job site on factory tune with no issues.

Back to PHP #2 tune without mods (load previous settings = NO) for the trip home (50 miles) with no issues.

Hex code and serial number should be in my profile.