Cruise control funniness

[wengenstein]

I have a problem with the cruise control on my 540i. I've searched on the topic but I haven't found anything relating to my specific symptoms. (I'll prolly chech the typical cruise control failure points anyway, as the older threads suggest)

When Accel.'ing, i.e., holding the stick in the forward position, the car will accelerate for a second (litteraly) then stop, accelerate for a second, stop, accel., stop, etc. This happens a few times until it eventually accelerates constantly and I get to the speed I'm looking for. This is also occurs, of course, when I try to resume. I push in on the control and get this intermittent acceleration.. Anyone ever seen this before? Any suggestions on what I ought to check first?

This only started happening last night...the temperature last night also happened to be the coldest this car has seen all year (between -12C and -14C).

[ukm5]

id check the acutuator motor the thing for pulling on the throttle cable, perhaps its playing up - presuming of course your speedo is working as it should and its not a faulty speed sender

[shogun]

I thought it does not have and works fly-by-wire with a poti under the accelerator pedal and a motor on the throttle valve, like my V12 engine.
Does it not have EML?

Often the synchronisation of the switches of the brake and the cruise control is the case of such trouble.

Edit: just found another success story on roadfly:

In the end, it was just the switch mounted on the column. SInce the car sat on the used car lot for over a year, it corroded up the contacts within the switch itself. I pulled it out, carefully disassembled it and cleaned the contacts. A nice lube of dielectric grease and the cruise is now fully operational.

[wengenstein]

I've noticed nothing wrong with the speedometer. How might I go about testing the actuator? I should probably go refer to a manual right about now :)


Thanks,
Dennis


id check the acutuator motor the thing for pulling on the throttle cable, perhaps its playing up - presuming of course your speedo is working as it should and its not a faulty speed sender

[ukm5]

I thought it does not have and works fly-by-wire with a poti under the accelerator pedal and a motor on the throttle valve, like my V12 engine.
Does it not have EML?

Often the synchronisation of the switches of the brake and the cruise control is the case of such trouble.

nope it should have an actuator, part number 2
http://www.realoem.com/bmw/diagrams/k/315.png

[shogun]

Thanks,
did not know, have few experience with the V8 engines.

[tim s]

there is two pins that you send 12 volts directly into on the actuator to test the motor. i do not remember which 2 pins. i had tested mine last year.
my cruise acts the same way, but i need to test the brake pedal switch next.
tim s.

[BrianH]

How much play is there in your cruise cable? The cruise and throttle cables are both attached to the throttle body by a bracket. Pull the inner part of the throttle cable (the actual inner cable) and see how much free play is in the end of it. Make sure the cruise cable has the same amount of free play. Mine has 3-4mm of play in each, and my cruise works fine. You adjust free play by turning the threaded collar on the end of the cruise cable. Always check the easy stuff first...

[ukm5]

How much play is there in your cruise cable? The cruise and throttle cables are both attached to the throttle body by a bracket. Pull the inner part of the throttle cable (the actual inner cable) and see how much free play is in the end of it. Make sure the cruise cable has the same amount of free play. Mine has 3-4mm of play in each, and my cruise works fine. You adjust free play by turning the threaded collar on the end of the cruise cable. Always check the easy stuff first...

there shouldnt be any play, otherwise u loose travel on the accellerator, albeit millimeters but still loose it

[ukm5]

How much play is there in your cruise cable? The cruise and throttle cables are both attached to the throttle body by a bracket. Pull the inner part of the throttle cable (the actual inner cable) and see how much free play is in the end of it. Make sure the cruise cable has the same amount of free play. Mine has 3-4mm of play in each, and my cruise works fine. You adjust free play by turning the threaded collar on the end of the cruise cable. Always check the easy stuff first...

there shouldnt be any play, otherwise u loose travel on the accellerator, albeit millimeters but still loose it..in any case the actuator would just keep pulling up the slack till the engine got up to speed so unless its a massive gap that wouldnt cause it