Thread: TD5 Disco Auto Transmission hesitation / jerk

I would like to know what the cause of this hesitation is.
It has never happened when driving normally, just the one time that I pushed it hard.

it's not over boosting is it, this will cause a kangaroo hopping like effect.

Your auto is an electronically controlled unit, everything is controlled by a computer.
I don't know if your model has a dipstick to check oil levels, if it has follow the directions in your owners manual or sometimes instructions are stamped on the dipstick.
Too much or not enough oil will cause problems, also check if the breather from the top of the gearbox is clear, breather pipe usually ends in a U bend on the firewall near the rear of the engine, good luck, Regards Frank.

Hi RoverV8 and Frank, Wow - that was quick!


I don't know how to check for over-boosting, but at least I know now that it could be a factor. Turbo unit has not been modified, except for replacement of the boost component by a competent and very experienced workshop. Engine ECU has been reprogrammed (same workshop), but I was assured in a way that would not overstress the engine or transmission.


Frank - no auto trans fluid dipstick in my Disco, but I have been underneath it to check fluid level at the filler plug several times. Filled to specs. The breather tube is there on the firewall - I suspect that it connects to diffs as well, but I guess I could try blowing through the firewall end - would that tell me anything useful?


Thanks, Andrew

Hi, you say the ECU was reprogrammed does it implies the injector codes too? , (which means they should have remove the rocker cover, read the actual injector codes and save them in the ECM), if yes a tester session on live data would reveal things... is the EGR still on or bypasssed?, when you say "boost component" what do you mean, wastegate modulator maybe?

some checks to rule out things:
1. make sure that fuse F2 in engine bay is good
2. unplug the MAF and see how it goes this way

If you cant blow through either the diff or gearbox breathers, you may end up blowing oil seals, esp. the diff.
I have never worked on the electronic ZF Auto, but if it has a breather and it's blocked, then I would imagine it may cause a problem, not saying it will cure your ills, but try the things that don't cost you anything first, Regards Frank.

Sounds like it is over-boosting; the symptoms are similar to those that you get when a vehicle is starving of fuel. What happens if the Engine ECU detects an over-boost is that it cuts the fuel flow at the injectors until the over-boost condition stops then enables the fuel flow again. Under acceleration this cycle happens rapidly giving a jerking motion.

Check whether the wastegate actuator is operating properly or sticking by applying about 15psi air pressure at its air inlet fitting. If it moves freely then check that the waste gate modulator hoses are connected. A nanocom or similar will help diagnose whether the modulator or the actuator is faulty.

If the hesitation problem happens at full acceleration at high revs , say 3900, then the problem I had was that the MAF was over reading and the MAF signal was going to zero in the ECU as it was out of the normal range.
This caused the engine to momentarily cut out, start , cut out, then a gear change.
This may be your problem if that is what you are experiencing.
Regards Philip A

If it's only doing it under heavy load/acceleration and at higher rpms I would be starting with the air flow sensing system and suspecting an overboost constionnfor the reported airflow rate.

It might also be the "throttle feathering" the ecu applies when the torque converter is attempting to lock up some remaps on some engines are a little aggressive in its application.