Any suggestions with throttle problems

New member so forgive me if I have missed the problem somewhere in the forum. I am having a small problem with my throttle in my 2002 disco td5. When you release the pedal under normal driving the engine still runs for a second or two then the engine slows as normal but there is quite a thud/jolt when it does, also if you hold the pedal in the cruise position (not pressed fully or released fully) the engine seems like it is missfiring and sounds like a 20 year old diesal ford I used to own. Here is a list of things I have already done, READY:
1. new head, was leaking diesal into sump
2. new fuel regulator, was leaking
3. new injector harness, oil on ecu but has now been cleaned
4. new wastegate control valve
5. sprayed wd40 on wastegate to free it up
6. replaced egr
7. removed throttle pedal to spray with wd40

As you can see I am running out of ideas and need some help so any suggestions.
Look forward to hearing from you.

The throttle pedal can give probems as it has a potentiometer and is linked to the ECU. You might get the engine check light on if it was the throttle and there would be 'driver demand' faults logged in the ECU.

Another think to check is the clutch switch. This is in the clutch hydraulic pipes in the region of the drivers side inner wing. The clutch switch makes the ECU cut revs as soon as the throtte is released. This gave problems on mine and the car would over rev on dipping the clutch. The part is about a fiver from LR and easy to fit.

The lumpy running could be do do with legacy oil still tracking to the red ECU plug.

It would be a good idea to give the MAF sensor a gentle clean with some contact cleaner. Careful though as the little filaments are easy to break.

Also, have you cleaned the MAP sensor on the inlet manifold since removing the EGR? If this is bunged up it will affect the running.

A fresh air filter and fuel filter would do no harm.

Cheers, Andy

Hi Andy, thanks for the reply. I have cleaned the MAP sensor but not the MAF so will do that, and will also replace the filters cos like you say can do no harm. Will look at getting a new clutch switch aswell but I forgot to mention earlier that when you pull up at say a junction, the engine has a rough idle but will calm down after a while. I wounder if I should invest in a fault code reader aswell.
Many thanks, James.

Jimmy80 said:

Hi Andy, thanks for the reply. I have cleaned the MAP sensor but not the MAF so will do that, and will also replace the filters cos like you say can do no harm. Will look at getting a new clutch switch aswell but I forgot to mention earlier that when you pull up at say a junction, the engine has a rough idle but will calm down after a while. I wounder if I should invest in a fault code reader aswell.
Many thanks, James.

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If you bought an item such as Nanocom, you would have a much better chance at effective diagnosis, rather than changing parts piecemeal.

There is a new Nanocom coming out the first 2 weeks of May, here is their site www.nanocom.it Existing unit costs about £230, don't know the price for the new one.

Hi, thanks for that. I will go to the site and have a look. Although they are expensive they do make it simpler to diagnose the problem saving you money in the long run by not having to buy parts you dont need.
Regards, James.