OK, I got a new one on my Discovery. When I step on the gas while the car is in reverse, the engine revs up even when you take your foot of the accelerator pedal. The first time it happened I was climbing up some stairs at Little Moab. It was a little un-nerving being pushed backwards down some rock stairs with a drop off on one side but back to the story. Now, ever since then any time you accelerate in reverse the engine want to keep revving. Once you stop and place the car in neutral, it revs to about 2000-2200 rpm and won't go down until you give the pedal a good stomp, then it will return to normal. When you back up without pushing the pedal it stays in idle. In drive the car acts normal with the exception of on cold starts the idle would sometime "pulsate". I have changed the IACV valve and cleaned the airflow sensor and the cold idle problem seems to have gone away. But the reverse problem is still there. Any Ideas?? The Disco is an 03.

 

Fault code numbers???????

 

Sorry, forgot that part. P0101 and P0505. But, after changing the IACV and cleaning the MAF it has not thown any codes yet but still has the reverse problem

 

Linkage putting stress on throttle cable? Busted motor mount?

 

I would check the throttle cable real well, sounds more mechanical the electrical

 

Strange..replicate the problem and while its still at high idle open the hood and manually close the throttle body. If the idle returns to normal you know its a mechanical issue such as a dirty throttle body, cable, ect.

 

I'm with Buzz here. Sounds mechanical. If motor mount or other parts are loose or have too much play, you could be pulling on the throttle cable if the engine is torqued a different way (such as in reverse rather than drive). I had to tighten up my cable on the 00 and there was a ton of play.

 

If you have a live data scanner, you could watch the TPS %. Let us say it is 9% in your driveway. If when you have everything flexed and and it does not return to same point, then it could be something mechanical loading up the linkage, which turns the throttle plate which turns the TPS sensor. BTW it does not go to "zero". TPS sensor has three leads that all go back to ECU. guess you could also have a "rub" where insulation is worn away and grounding out.

 

Dirty throttle body, sticky throttle linkage, any one of the things directly connected to the throttle.

 

Ok, I think I have it fixed. You guys that pushed for a mechanical problem were correct. After you guys suggested mechanical, I took a hard look at the throttle cable. I noticed the cruise control cable seemed to be pretty tight. I referred to rave manual and adjusted both cables (throttle and cruise) to the spec referred to in the manual. I believe I had a couple issues at once. I was also swapping out my IACV and have decided one of them is bad. After I got the cables adjusted and the "good" IACV in, the idle has been very good and stable. The vehicle is still pretty new to me and I realize it has been idling a little high the whole time I have had it. I have owned a 95 for many years and should have put 2 and 2 together but, I drive the 95 and my son drives the 03 so I did not catch on to the high idle. Thanks for all the help from everyone!! Sure nice to have access to lots of knowledge!!