Puma Limp home. No Codes. Re-boot fixes

[Brid]

Wondering if anyone can suggest possible cause(s) please?

My 2007 Puma has 312,000kms and has gone into limp mode once 7 months ago, and again yesterday twice in short succession.

On each of the 3 occasions, I was on the highway to work doing around 80kph, and slight depression of the accelerator to increase speed with the traffic and I can sense no response! Zero! The pedal does nothing. All I can do is keep it going with hazard lights until I can get onto a safe spot.

Switch off engine - Pause - restart and it's perfect again! Immediately after the re-boot, it really accelerates strongly, to get back into the traffic! You absolutely cannot fault it!

The Scan gauge doesn't detect any faults. Temperature is a bit cool (thermostat has been stuck open for years), so definitely NOT overheating.

I've had limp home mode before when coolant level dipped below the expansion tank...but this did not need a re-boot.

Basically the engine is in excellent condition with very good acceleration when needed, and good economy (9L/100km normal running around). It has a BAS re-map with EGR delete, so can rule out EGR issues.

Needless to say, with a 7 month interval between problems, I'm stumped and would appreciate any and all thoughts.

Cheers

[Marty90]

Later Defenders go into limp mode if you drive them a little harder when cold,and if you're going up a steep hill on the freeway and the temperature rises slightly. LR think of everything😁
If your thermostat is stuck open,not a good thing! Better get it fixed.

[Brid]

Later Defenders go into limp mode if you drive them a little harder when cold,and if you're going up a steep hill on the freeway and the temperature rises slightly. LR think of everything😁
If your thermostat is stuck open,not a good thing! Better get it fixed.

Thanks Marty
Unfortunately neither is a factor in my case...no hard running nor high temps.

[Toxic_Avenger]

My guess- Accelerator pedal position sensor (APP).
FSM says it's a dual rotary potentiometer- ie power (volts) goes in, less power comes out and goes to the ECU/ECM for makign things happen (simply put). Sounds like a dual redundant circuit, for safety etc. So probably 2 pins at the ECM (but I haven't looked over the wiring diagram).

FSM also mentions that if one input from the APP fails, then engine response is limited to the first 28% of pedal travel.
If both inputs fail, no bueno. Also mentions that you'll get a high idle, and idle drops to normal when brake pushed (so once you stopped, you'd probably not notice anything was amiss!).

For it to go FUBAR like it did- intermittantly- I'd probably trace the wiring to the APP, and From the APP to the ECM. Something it probably dicky.
Do the old wiggle the loom and try to force the problem trick. I reckon you'll have some luck. Obviously not while driving... but have it idling with handbrake on, and try to force the high idle symptom.

Brake pedal switch failure can also work with similar symptoms as the single pot track failure on the APP (28% pedal response)... so also keep that in mind.

[Toxic_Avenger]

Couldn't help myself... looked at the wiring diagram.

Power to the APP comes from the ECM and returns to the ECM via plug C0872 on the ECM (should be the middle big plug on the side of the ECM which is in engine bay, on the firewall behind the engine).
6 wires in total for the APP:
2x Black wires (ground)
1x Red/green trace wire- Pot track 1 power wire ('to' APP)
1x purple wire- Pot track 1 sense wire ('from' APP)
1x White/grey trace wire- Pot track 2 power wire ('to' APP)
1x white/greent race wire- Pot track 2 sense wire ('from' APP)

Experience with other cars is its often a 5V signal, and something less than 5 return, depending on the scale/resistance of the potentiometer.
If it is in fact anything to do with the APP, then its most likely wiring, possibly ECM intermittantly wigging out, and least likely a failure within the sensor.

Good luck.

[Dorian]

In my research on my recent problems, I came across many references to a similar problem with older rangers and transits, go to accelerate, limp mode no fault codes.
End result was faulty temp sensor on fuel pump.
I know that LR do their own programming, but I'd put pound to a penny that they lay their stuff on top of the ford program.
If you get no joy elsewhere might be worth considering.

Cheers Glen

[Brid]

Thanks Glen and Mitch
Sorry for the lag in reply. Was out of the loop on the W/E. Electrical is one of my weaknesses, but I'll look forward to checking those out.
Cheers
Brid

[n plus one]

Look into the SCV - sounds like it could well be your issue

[justinc]

Scv fault usually also gives a very poor idle and difficult starting.

[n plus one]

My experience is that it certainly ends up like that, but with my Puma it just started as intermittent loss of power without any other signs (starting, idling, etc) before progressing to rough idle and more frequent loss of power, before eventually stalling, etc.

Based on the UK Transit forums they typically last somewhere in the order of 100k miles.

[Brid]

The SCV was replaced last year. It always starts very well...almost instantly and idle is also very smooth and quiet. Only varies by about 5-7rpm, by the scan gauge. It just behaves perfectly, except for these very rare events, where on each occasion, it has gone into limp mode with a slight throttle increase from around 80kph as the traffic speed picked up slightly. No doubt it'll get worse eventually, which will make it easier to diagnose, but in the meantime it could be a hazard.

[Dorian]

Not that you want to keep it as part of you plan, but in a pinch, you can turn the engine off and reset the limp mode while rolling. Not fun but better than weaving thru traffic while loosing speed

[Brid]

Yes Dorian...that had occurred to me as well...just not game to do it in case steering locks...might be a wuss!

[Brid]

I did find one connection (fuel rail pressure sensor) that appeared to be not fully connected. Having pushed if in firmly, I have not had any further issues for the last 6 weeks. It's certainly a likely cause of my problem. Time will tell if it is, I guess.

[Marty90]

Look into the SCV - sounds like it could well be your issue


What's an SCV?

[eckwalsh]

Regardhave symptoms like it is running out of fuel. My 2008 had done yhis a few times over the years and bith times ended up being like a vasaliine looking stuff blocking the fuel lines on the pick up inside the tank.
Regards

Eric.

[ozy013]

What's an SCV?

Suction Control Valve or you may hear it also refered to as Volume Control Valve