sweet_87_iroc

iTrader: (3)

I am about to take my car back to Michigan from north Carolina. I noticed that when I set my cruise the car will slow down considerable and then surge to get back to the set speed. It will continuously do it this while it's set. Any ideas would be great!

paulo57509

Check your vacuum hoses for leaks is a good place to start.

If you've had the cable at the throttle body removed recently, check its routing and adjustment at the servo.

sweet_87_iroc

iTrader: (3)

I should be able to check for leaks with the car running and the cruise not engaged, correct?

gearhead141

Just curious if you found that you had some leaky vacuum hoses. I have the same issue on my stock '85 T/A. I replaced the hose going from the "T" down to the vacuum tank but have not replaced any of the other hoses. My car will drop from 70mph down to below 65 and then pick back up to the set speed. Please let me know if you solved your problem.

gearhead141

I'm not sure if the original poster got his problem fixed. My solution was to replace two very decayed vacuum hoses. The one going up to the cowl which is about 3 ft long as well as the one going to the cruise unit; only about 8 inches long. Once both of these were replaced, the cruise control works perfectly. The short hose was so rotten that it was collapsing! My car is slowly coming back from being in storage for over a decade which means replacing a lot of rubber pieces.

Ozz1967

iTrader: (4)

Look at your cruise bellows, where the cable hooks to it. Do you have a ball-chain or a solid screw-in connection?

My 84 had the ball-chain style until it broke. If the ball chain isn't set tight enough, it'll drop speep until the slack is taken out of the ball-chain, then catch up.

When mine broke I had to get a cable out of a later year car but it doesn't fit the bracketry quite perfectly. Still works fine though.

gearhead141

[quote=Ozz1967;5652065]Look at your cruise bellows, where the cable hooks to it. Do you have a ball-chain or a solid screw-in connection?

My cruise unit has the solid screw-in connection from the cable. My commute is 23 miles and on the way home yesterday I set the cruise at 67mph and it stayed there for the duration of the drive. Just for comparison, I looked at the cruise unit in my '96 GMC truck. There is no comparison. More modern technology did away with any vacuum hoses.