Hi:

New to forum. Always buy good used vehicles. Never had a Ford. Won't buy GM or Dodge because of bailout. Enough politics.

Ford F 150 supercab 4.6 L Triton, automatic transmission.

I was driving up to visit my son and passed a slow moving truck pulling a grain wagon. Kicked down fine etc. About 5 miles later was at stop. When I took off would not shift out of low. I manually put it in second and it shifted. Put it back in drive and it stayed in second. Check fluid= fine. Drove about 20 miles in second and stopped at a gas station. When I went to start engine, all the lights came on and cranked but it would not start. No indication of firing. It did this a total of 4 times. On the fifth try it started fine. I drove away and it shifted normally.

A couple of weeks later I was on the freeway and passed a truck (kicked down). I went off my exit and stopped. When I strarted to go it did the exact same thing stuck in second gear. When I got home I shut it off. Tried to restart and again nothing for 4 times then the fifth time it fired up and drove normally shifting fine.

The book says the transmission is "adaptive" and adapts to the drivers habit.
I hope it was not adapting to kicking down until a 4 times power off reset.

Anyway, I called dealer service and they never heard of such a thing. Searched internet and found nothing.

Anyone's help appreciated.

Best regards

Robert

 

Welcome to the forum, Robert. No, the "Adaptive Learning" is not something that does what you describe.

This sounds like a speed or throttle sensor problem to me.

The normal upshift/downshift change depends on both vehicle speed and throttle position. At a fairly open throttle (not full throttle, but slightly aggressive acceleration), the upshifts will occur at a higher speed and downshifts will do the same (as in climbing hills). If the throttle is only slightly open, up and downshifts will happen at lower speeds.

Since you don't say anything about the speedometer being "stuck", it could well be a throttle position sensor problem. But, this should also cause your engine RPM to be stuck too.

Since it shifted into 2nd when you manually put it there, I doubt the problem is in your transmission itself. But, since the truck is "drive-by-wire", I think this is something for a dealership to troubleshoot.

Good luck!

- Jack

 

What year?

The transmission is controlled by the ECU, there's no separate transmission computer except in the 6 speed in the 2009-2010 4.6 3 valve.

Drive by wire is only in the 04+.

 

2002. What is meant by: Since you don't say anything about the speedometer being "stuck", it could well be a throttle position sensor problem. But, this should also cause your engine RPM to be stuck too.

Stuck? Both speedometer and rpm varied with speed of vehicle Driving 50 was about 3000 rpm. I don't understand the use of the term "stuck" in this context.

I guess I will have to take it into a dealer. Hopefully I can get it to malfunction with a mechanic on board. When I described condition to dealer/service they said they never heard of such a thing.

Best regards

 

The TPS doesn't affect the speedo/tach on a 2002, and it uses a conventional cable throttle. If the VSS were bad, the speedo (but not the tach) would be affected, as would the transmission strategy.

If you were showing 3000 rpm at 50 mph, you were "stuck" in 2nd gear.

Have you read out the OBD2 for possible trouble codes? Has the CEL ever come on? Has the OD Off light in the shift **** ever started flashing?

 

By "stuck", I meant they would not be changing in line with the actual vehicle speed or engine RPM.

But, as glc pointed out, I SHOULD have asked your model year. Somehow, I assumed the truck was a later model than 2002. Stupid me.

I still doubt this is a PCM problem, but a sensor "lying" to the PCM could cause your problems I think. The PCM has to react to the various sensors that feed it data.

I wonder, glc, if a poor electrical connection at the VSS could cause this? Especially since it seems to be "intermittent".

- Jack

 

I would think an intermittent VSS would affect the speedometer.

 

I know, I'm grasping at straws here. I just can't see the PCM having a fault in part of its program and still be fine everywhere else.

I can believe the dealership has never heard of anything like this.

- Jack

 

Jack, maybe you should move this to the Transmissions forum so the experts see it. Maybe Darrin has an idea.

 

Good idea, as always, glc. Thanks - I'll do it now.

- Jack

 

Scratch what I just said if you got a notification that I said it. Coffee hasn't reached the brain yet.

New plan! Start with the MLPS, otherwise known as the Neutral Safety Switch

If you replace it or check it for proper alignment, make sure the marks align like they do in the link below with the transmission in NEUTRAL.

http://www.bcatransmissions.com/properalignment.jpg

D

 

I'm far from being a transmission expert - so take this with a grain of salt.

I could understand the MLPS causing weird transmission behavior, but a crank/no start? I could see a NO crank.

 

Nope, you're right. I skipped right over the part about it cranking and just saw no start. A bad MLPS would cause it not to crank.

So....

Back to my original idea. This is an electrical issue and those are the hardest to diagnose. Online help likely isn't going to cut it. I would start by checking the computer harness and main harness connector in the engine compartment. Disconnect, inspect, blow out and reseat them. Make sure they are tight.

Good luck with this one. I hate electrical issues. Particularly intermittent electrical issues.

D

 

Update. Happened again today after trying to pass slow car in 35 mph zone. More info this time.
After I pulled over I let it idle. Idle speed 1250-1350 rpm. I shut it off. Tried restarting. Again cranked and no firing. This time about 10 trys before it started then everything normal idle about 700. Really weird. The idle speed might be a clue.

 

OBDII showed no code.