Cruise Control issue

[Whitaker717]

Hi Guys,

I just recently had my cruise control kit installed on my 87.  I have my speed adjusted almost right on. The issue i am running into is when i go up a steady incline hill with my cruise set i lose like 10mph. So if i have it set at 65 by the time i reach the top i am only going 55 mph. Its not a super aggressive hill either. My question is has anyone else had this issue and what is the fix for it? Its an 87 auto with fairly stock tires and factory gears. Pretty well stock. Thanks guys

[87MJTIM]

When mine was working, that happened all the time.

 

Is yours a 4.0 or 2.5? 

[eaglescout526]

Yeah I experienced this yesterday driving on the 101. It’s normal for it to lose speed. It will catch up.  

[Whitaker717]

4 hours ago, eaglescout526 said:

Yeah I experienced this yesterday driving on the 101. It’s normal for it to lose speed. It will catch up.  

I figured it would lose a little speed but 10mph seems a bit much to me. I'm wondering if i have a vacuum leak or something. I'm not really sure.

[Whitaker717]

5 hours ago, 87MJTIM said:

When mine was working, that happened all the time.

 

Is yours a 4.0 or 2.5? 

4.0

[87MJTIM]

With a 4.0 auto, you should have 3.55 for gearing.  Not the best, but better than 3.07 with a manual.  Since the CC system operates on vacuum, as the engine strains to go up hill in a given gear, it will loose some vacuum.  The CC will suffer.

[eaglescout526]

Well you gotta think, cruise needs more vac to pull the throttle. So what you need to do is help cruise anticipate the up hill by giving it some gas to help keep the speed. 

[Airborne Janitor]

I'd wager you have a vacuum leak somewhere. I'm running 33s with 3.55s and this doesn't happen to me. Check the defroster vents to see if air is blasting out of them when your cruise is pushing the limit. Check for cracks in your vacuum lines and vacuum canister. Install an inline vacuum check valve (GM 14047619) near the intake manifold.

[pizzaman09]

+1 on the vacuum check valve inline near the intake manifold, if you have a good accumulator and no leaks it should work well.

 

I'm guessing you have the adjustment trims on the yellow computer tuned well for your setup?  You could get the same symptoms by having the low speed adjustment or centering adjustment off.  Possibly sensitivity but I doubt it.

[Whitaker717]

11 hours ago, pizzaman09 said:

+1 on the vacuum check valve inline near the intake manifold, if you have a good accumulator and no leaks it should work well.

 

I'm guessing you have the adjustment trims on the yellow computer tuned well for your setup?  You could get the same symptoms by having the low speed adjustment or centering adjustment off.  Possibly sensitivity but I doubt it.

My speed when I set it is spot on. So my centering is fine. I thought the low setting was just for when it engaged at say 30mph. I could be wrong though. I must admit though I still have no idea what the sensitivity screw does. It is as far clockwise as it will go. 

[Ωhm]

Make sure TCC/CC SW is adjusted properly. Button needs to be pushed in, in order to seal vacuum.

 

 

[Whitaker717]

4 hours ago, Ωhm said:

Make sure TCC/CC SW is adjusted properly. Button needs to be pushed in, in order to seal vacuum.

 

 

So the button has to be pushed in while the brake is not compressed, correct?

[eaglescout526]

1 minute ago, Whitaker717 said:

So the button has to be pushed in while the brake is not compressed, correct?

Yes. The goal is to make it completely vacuumed and when you push on the brakes, that valve dumps all the vacuum and stops cruise control until you resume operation. 

[Ωhm]

2 minutes ago, Whitaker717 said:

So the button has to be pushed in while the brake is not compressed, correct?

 

Yes

[Whitaker717]

4 minutes ago, eaglescout526 said:

Yes. The goal is to make it completely vacuumed and when you push on the brakes, that valve dumps all the vacuum and stops cruise control until you resume operation. 

So from the picture above, does that look ok or should it be pushed in more? 

[Ωhm]

Truly, the only way to tell is disconnect the vacuum hose and connect a vacuum hand pump. See if it holds vacuum.

[Whitaker717]

So i just walked down and checked. The button is adjusted properly. It is pushed all the way in

[eaglescout526]

9 minutes ago, Ωhm said:

Truly, the only way to tell is disconnect the vacuum hose and connect a vacuum hand pump. See if it holds vacuum.

Blowing into the hose works too. 

[Ωhm]

2 minutes ago, eaglescout526 said:

Blowing into the hose works too. 

 

True, good idea. Easier.

[Whitaker717]

18 hours ago, eaglescout526 said:

Blowing into the hose works too. 

Which hose?

[eaglescout526]

The bigger one from the solenoid to the dump valve. 

[Whitaker717]

22 hours ago, eaglescout526 said:

The bigger one from the solenoid to the dump valve. 

Dumb question i know, what is the solenoid and dump valve. Is one of those the football. LOL

[87MJTIM]

 

The servo, #2, is the other end of the vacuum line.

[eaglescout526]

Yeah the servo sometimes called the solenoid and the dump valve is the valve that’s installed at the brake pedal. 

[Whitaker717]

9 hours ago, eaglescout526 said:

Yeah the servo sometimes called the solenoid and the dump valve is the valve that’s installed at the brake pedal. 

So I just blow into the big hose connected to the servo? How will I know if it holds