Robert Lavigne

I have an 86 951. The cruise control motor went on it, so I managed to get a 87 951 cruise control motor at a great price. Everything works okay in that it now powers the components. However, upon activation, it spikes up about 5-10 miles an hour (10-15 km/h). Is there something to adjust this or is it simply that the 87 is responding differently to the signal.

Rob

Michael Stephenson

Mine does the same thing, most of the time.

I typically set mine about 5 mph lower than I want to go, knowing that it will speed up a bit.

But I have a theory: The motion that is used to set the cruise is the same motion that is used to increase the speed. So, if you linger in setting the cruise, then the unit might think that you also want to accel. Sometimes if I engage the unit with a real quick flick of the lever, the speed will no go up. Again, this is just a theory.

Longtime76

My control seems to do the same thing as well. It does seem easiest to set it a bit lower than what you want. I think Michael is right though, if you hold it down for any time at all it thinks you are wanting to accelerate.

Perry 951

Check the tension on the cable. I have seen many, mine included, that is a little loose. Get it to lift the throttle off the idle stop (you'll hear a click), then back it off just so it clicks the switch back closed. It helped a lot on mine.. ~2 mph varient. However, mine will go to full throttle by itself sometimes when the temp is below 32. Very strange and sometimes frightening. It will accell until you turn it off, or until it blows up!

Tom R.

Mine does the same thing especially when I want to set the cruise to 40 by a speed trap (where I am the Judge, and it would be very emabarrassing).

I almost gave up on using the cruise control alltogether.

Can I get a little more detail on the cable fix, Perry?

Thanks

rpm's S2

There was thread on this 'surge' prblem a while back. Several posts, mine included, noted that the problem seemed much more frequent in cooler weather. That has been true for me all summer - no problem except one cool rainy day when the cruise would have taken the car over 100 mph if I didn't cancel it. Weird

Michael Stephenson

My original cruise box would cause to accelerate at full throttle. Sometimes it would level off and surge, decel, surge, decl – other times it would just keep on going faster and faster.

I replaced the box with a used one and I no longer have that problem.

There must be something in these boxes that go bad, sounds like it may be limited to one or two problem parts since our experiences seem to be similar. To bad I don’t know more about electronics or I would track down the problem.

Perry 951

Tensioning the cable is not hard.

On the actuator side (pass side in front of battery) there are 2 nuts on the cable that lock it to the bracket. Loosen the one on the motor side and push the cable towards the outside of the car until you hear the throttle click (might have to lean a bit and stick your ear by the throttle body). When it clicks, tighten the outer nut. Then, slowly back off the outer nut until it clicks again. Tighten the inner nut and you are set. You may also want to do the same for the throttle cable itself. This way all is tight. Once you get in there you will see what I mean.

The clicking noise is the idle switch. It indicates to the DME that the throttle is all the way closed.

Mike

My cruise control works fine. Locks in at the speed it's set at and stays there OK.

Sounds like you have a problem...rumor has it that the components on the circuit board inside the "brain" unit often need resoldering.