Surging?

[zeroboot]

had a similar issue...'05 4.4. I brought it in several times for transmission issue, always the same thing: jerky shifting on startup, and also the occasional 'lurch\clunk' that feels like getting rear ended.

Initially they did a reprogram..didnt work. They also couldnt reproduce any of what I was describing so it didnt go too far.

Just recently I brought it back again with the same complaint. They were finally able to reproduce something, so they opened a PUMA case. The end result of all that was that they agreed to replace the tranny under CPO warranty!

[Isambard]

Thanks for the input zeroboot, but this is a different 'kind' of surging.. Its not tranny based, that I am certain of.

The reason I say this is because you have described it as 'jerky shifting'. Mine, and I'm quite sure its o.l.t's symptoms also, has nothing to do with the shifts (up or down), it simply lurches forward whilst in the same gear if you have your foot at a constant on the gas pedal. Always from cold. There is no lunge or surge, or even any clunks (the clunks when down-shifting could be your rear subframe bushes) when up/down shifting.

Which, while I write this has made me think it may have something to do with the ETC or at least along those lines. Seeing as this is drive by wire, I'm wondering if there is something defective within the ETC system that is making the 'surging' on-off-on-off effect whilst the accelerator pedal is placed at a certain point.

Someone could ask the question 'why does it happen only when cold, why doesn't it happen any other time?' Maybe because when the motor is cold, things are more 'sensitive' and any small differences are simply exaggerated and so translated into this surging/lunging feeling...?

Could there be something in what I am saying or am I talking bollocks?

[Weasel]

Isambard, if the surging felt is while cruising around 40mph-ish it could be transmission related. What happens is the torque converter lockup clutch circuit acts up and doesn't fully engage the lockup clutch, but pulses it momentarily repeatedly about once every second or so. The fix for this is to replace the mechatronics unit (valve body).

A quick way to confirm it would be to get it doing it, then while maintaining the same speed shift into sport mode. It should stop doing it. If memory serves it may do it in sport mode at a higher speed, like 55-60 mph?

[Isambard]

Thanks Weasel I understand what you're saying but I havent reached anywhere near that speed when it happens. Like I said previously its from start-up, up until the first 200 yards only. After that all is well.

There's no way I'm doing 40+ from cold, and at only 200 yards. I'll only be doing around 20, if that...

What I'm talking about is quite literally: start the car, put in D, drive out of garage, turn down my road-not even making it to 3rd gear, and by the end of my road before I make a right turn (approx. 200 yards from my starting point) the problem has cleared. All the above takes about 20 seconds.

The reason I believe it can't be the tranny is because it does not happen at any other time.

o.l.t, does this sound familiar?