If have the following issue with my Mazda Tribute. Normally I am drivin in the Netherlands (flat roads, no hills/ mountains). I have just been to the mountains and had some issues. The car doesn’t start to 'brake' on its own if I release the acceleration pedal while driving on a downward slope. A few times it starts to brake but with a small touch of the acceleration pedal it stopped braking. In general in doesn’t brake and it slowly accelerate by gravity.

I have had issues in the past with rpm. It came down really slow (from 3000rpm to 1000rpm idle). The car was under warranty and the Idle Air Control Valve has been changed. Actually it didn’t improve much. According the garage it is a typical Mazda behavior. Accepted the issues and I did care up to now.

I cant find the issue and need some help. I suspect the TPS (throttle position sensor). Can I test the sensor by myself? I don’t want to spend money before I am sure.

Any other people experienced the same issue? Could the TPS cause this problem? Any ideas were to search?

The car is not braking on downwards slopes by the engine. Even when I drive 2000RPM the speed (and RPM) are slowly increasing by gravity even without touching the acceleration pedal. Without driving, or declutched or with flat roads the RPM coming back to 1000RPM (idle setting). Only a typical issue on downward slopes.

Awaiting some help. Thx, Mike

 

To the best of my knowledge, your Tribute does not have an engine brake. Downhill brake assist, for those vehicles that have it, only operates at speeds under 20mph. Mainly for the 4x4 crowd that plays in the mountains. I don't want you to start throwing parts at your car trying to fix something that it's just not capably of doing.

 

Disagree with your reply. Downshifting, which allows "engine braking" to control the vehicle's top speed, is the way to drive on steep terrain. Engine braking uses the engine's compression to apply resistance to the drivetrain. I my case the engine RPM's are increasing and engine is not braking. So, it is increasing speed. Even with 4000 RPM and accelerator pedal released, steep slope, engine doesn't want to reduce rpm's.

 

Yes you will reduce some speed by downshifting, But at some time, the hill grade and gravity will be more than engine drag will be able to overcome. A semi truck, with an engine brake added to it, still has to choose a much lower gear at the top of the grade to start in, or their speed would increase to a point where the engine brake would be overcome.

 

Over the last couple of decades automatic transmission technology has changed such that engine braking is being reduced to the extent of being all but eliminated under most driving scenarios. The thing is, in the never ending quest for improved fuel economy, torque converter technology has changed to effectively "open up" when the foot is taken off the accelerator pedal to aid the vehicle in coasting; thus improving fuel economy.

The description of the issue here doesn't sound like an issue at all.

 

Agree, but in my case I am sure it is something with the engine. We are not talking about high hill grades. So, back to the engine. What can cause this issue. A few times it starts to brake but with a small touch of the acceleration pedal it stopped braking on the engine. I have experienced more issues in the past by reducing the rpm from 2000 down really slow. Could this a bad feedback from the trotlle control sensor? Some people experienced this before?

 

It doesn't sound like there is anything wrong with the engine.

 

Did some research on the the internet and found the same issue. Unfortunately no solution..... Surging 2002 Mazda Tribute v6 - Car Talk

Any idea?

 

Problem solved!!! Vacuum hose from the back of the throttle body was degraded. Replaced TPS as well. Reset ECU afterwards. No issues anymore. Many thanks for all advices.