Throttle stuck wide open!!!

[DMC63]

I was traveling to the BMW festival yesterday along the M40. I was cruising around 70mph. I changed up into 5th and put my foot down a bit hard on the pedal and the throttle stuck open! The car shot from 70 - 110mph, shiiiiiiiiit myself completely, in a state of complete panic I eventually hit the clutch and brakes and managed to pull it back with my foot. Fortunately there was no one in front of me for a bit but it took what seemed like a lifetime to pull it back again. I've not been able to replicate this happening and I'm now very weary to drive the car. Has anyone else had this problem? Can anyone point out what the problem is? I'm going to remove the pedal later and have a look.

 

[MACK]

I have never heard of this before but from what your saying (or what I think your saying) the pedal clearly jammed. I would take it out and clean and lubricate it to see if I can get it back to a smooth action that springs back when you release it. Alternatively you may no longer have any confidence in the part at all and in that case I would source a used replacement. It might not necessarily have to come from a Z4, use RealOEM.com to see if the z4 part is fitted to other BMW models. Might be cheaper to get one ofF a E46 etc of some description if they share the part as Z4 spares have a tendency to be pricey.

 

[Ewazix]

The most common cause of this is a floor mat out of place or curling up and sticking. Several makers have had recalls in the past for oem mats and I've had exactly the same happen with a mat in a Volvo. It catches you out for sure! It can be difficult to replicate as the mat often goes down when you shuffle/lift off in the 'action'.

I've also had it on an a motor when the snail cam/linkage on the throttle body was jamming on fully opened so it's worth checking/lubing in there but my money is on a mat.

 

[EdButler]

The most common cause of this is a floor mat out of place or curling up and sticking. Several makers have had recalls in the past for oem mats and I've had exactly the same happen with a mat in a Volvo. It catches you out for sure! It can be difficult to replicate as the mat often goes down when you shuffle/lift off in the 'action'.

I've also had it on an a motor when the snail cam/linkage on the throttle body was jamming on fully opened so it's worth checking/lubing in there but my money is on a mat.

Both very good points, but highly doubtful on a Z4:

1. Mats getting stuck is usually a problem with top-pivoting pedals rather than bottom pivoting which the Z4 has. Either way, it'd be very hard for the mat to get so wedged to push the throttle nearly fully down. I would guess the OP would have noticed this when pulling the accelerator back.

2. Z4's have an electronic throttle-body. The accelerator pedal is effectively just a variable resistor for the ECU.

Do you have an automatic? It could be that the return spring for the accelerator was not able to push it past the kick-down switch friction? Either way, i'd be looking for a new pedal first off.

 

[DMC63]

Thanks for the replies, it's a manual. The mat doesn't catch it. I'll have to look deeper.