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Cruise Control Surging


Noka

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  • Member
  • Member For: 14y 17d
  • Gender: Male
  • Location: Geelong

My BF (06) XR6T ute has been playing up on cruise control. It is a 6 speed auto box with 110000km's.

I have found when cruise control is on, or when driving without cruise control but when engine under load (going up a slight hill), the revs bounce up and down between 1500 & 1700 rpm and sounds like the car is surging. Was also getting the same shudder that a manual car gets when in a gear too high and going to slow.

I took it to the transmission place to get a service and when dropped the pan basically the oil was water. Found the heat exchanger had sh*t itself and contaminated the oil with coolant. Basically rebuilt the auto (converter, clutch, plates etc...).

The reco has fixed the shuddering problem but the surging still exists. I have today replaced the throttle position sensor and still have the same problem. Does anyone know what may be causing this.

Over the last couple years I have been getting my ETC light come on and off randomly on the dash hence why I changed the TPS. The transmission guys have also managed to data log the ecu when driving and picked up the codes relating to the pedal position sensor, P2127, P2129, P2138 & P2140.

Will this somehow effect the yo yoing of the rpm when the engine is under slight load (going up a hill with cruise on or off)?

Thanks for any input!

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  • Donating Members
  • Member For: 18y 5m 6d
  • Gender: Male
  • Location: Melbourne, VIC

My car does the same... going up hill on cruise, it'll obviously try and maintain the speed, but it accelerates too much and then drops back again, then it senses its slowing down again so accelerates again and then drops again... Its asif it cant figure out a happy medium.. This is even on only slight hills too... I kinda only noticed it once I put some new parts on (bigger cooler pipes, cooler etc...) hasnt been tuned yet, but had it on the dyno and all is good.. Im thinking its tune related, well for me anyway..

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  • Sucker
  • Moderating Team
  • Member For: 20y 9m 2d
  • Gender: Male
  • Location: Brisbane

I don't think the ZF can be rebuilt properly after a 'milkshake' which is probably why you're still having issues, when it's a warranty job they just replace the whole lot as it causes permanent damage to the mechatronics module.

If you want to read more see... http://www.fordxr6turbo.com/forum/topic/75623-zf-auto-milkshake/

But that's mostly hysteria and not much fact unfortunately.

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  • Member
  • Member For: 14y 17d
  • Gender: Male
  • Location: Geelong

Mine has been tuned for a couple years now and not one problem. It has just started the past couple weeks and can not figure it out. I'm thinking it might be the motor on the throttle body might be a little sticky. I will be checking the pedal position sensors too. Maybe clean them with some contact cleaner and see if this helps.

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  • Member
  • Member For: 14y 17d
  • Gender: Male
  • Location: Geelong

no tyres have been changed. although I did get a wheel alignment and they said to keep the tyres at 40psi just before this started.....

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