c4 cruise control

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Mar 18, 2018 | 05:43 PM

wishitwascamaro

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c4 cruise control

I am the proud owner of 1985 corvette. The cruise control is vacuum actuated from the intake manifold and it just doesn't work very well. I also have a 1990 Chevy Silverado pickup truck that I am getting ready to have hauled away as scrap because the frame rails are badly rusted and just not safe to drive. The Silverado cruise control works very well, but it is electric. what do I have to do to retrofit this electric cruise control into the Vette?

Mar 18, 2018 | 06:52 PM

Joe C

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Quote:

Originally Posted by wishitwascamaro

I would think the first thing you would need is a wiring diagram or schematic of that Silverado's cruise control circuit. ECM's are apples and oranges, but anything's possible. most likely, IMO, you'll be opening a can of worms. good luck....

why not just troubleshoot and repair your 85's CC?

Mar 18, 2018 | 09:11 PM

wishitwascamaro

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Quote:

Originally Posted by Joe C

I probably will end up doing that- but I think the problem is not so much in the cruise control system but the engine has a high performance cam and after market throttle body with oversized throttle plates- this combination results in the engine having a low vacuum at any given throttle setting and the throttle plates are closer to the closed position at any given speed especially in overdrive, and the cruise control unit just doesn't have the kahoneys to pull the throttle open at 70 mph on the freeway

Mar 18, 2018 | 11:26 PM

Pwnage1337

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From: Custer, WI

I am looking at using the Dakota Digital Cruise setup simply because I don't want to screw with trying to make an antiquated system work. If your Digidash is screwed, you have to have that repaired, $$$. Then you have the issue of not having a servo that works, from what I've gathered the rebuilt ones are questionable.

Mar 18, 2018 | 11:41 PM

gerardvg

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From: Melbourne, Victoria, Australia

Quote:

Originally Posted by wishitwascamaro

Check the brake pedal switches, there is a vacuum hose switch and also an electrical one that is used with cruise control and the torque converter clutch circuit.

When my cruise control played up it was the electrical brake switch was faulty, one of the internal switch contact had broken.
The cruise control would cut out at random.

Note my 85 C4 is supercharged, I never had any cruise control issues due to low vacuum. Unless I used full throttle there was enough vacuum while cruising to use cruise control and brakes.

Note, the dash is used in the cruise control circuit.

Last edited by gerardvg; Mar 18, 2018 at 11:42 PM.

Mar 19, 2018 | 10:39 AM

ctomlin@amroc.us

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From: Eastern Pennsylvania

On my 93 the vacuum hose that went from the servo thru the firewall to the brake pedal switch had developed a small leak just outside the firewall. It was a small leak but enough to cause problems. Tough spot to work but replacing the hose solved the problem.

May 6, 2018 | 10:19 AM

wishitwascamaro

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Quote:

Originally Posted by ihatebarkingdogs

I've attempted to install a truck electric module into an earlier vacuum system. I was not entirely successful, and abandoned the attempt. The issues were with the VSS signal type, frequency, and pulse rate. The interface of the throttle vale cable will present challenges as well.

I don't think it can be done at all in an 84-89 Corvette. 84-89 cruise electronics are incorporated into the dash cluster. There is a VSS signal to the ECM, but I don't think it can be used for the Silverado cruise module. Different frequency. Everything else is electrical, and the connections are available, but you will need a FSM for both cars to figure out the wiring.

Having said all that, the cruise in my 85 works pretty well. Follow the advice given above. Check the vacuum hoses, and the switch adjustment on the brake pedal. If it works, but poorly, vacuum leaks are the most likely culprit.

Be sure the vacuum check valve at the plenum is not leaking. Ie, it holds vacuum. There should be sufficient vacuum in the reserve to operate the cruise, and the reserve will recover when the throttle closes slightly. My experience on turbocharged Syclones and Typhoons has been that the cruise will operate satisfactorily (hold the set speed) down to 2" vacuum.

Another thought: There are stand-alone electric vacuum pumps available. The ZR-1 uses one for the secondary throttle system. My 99 Powerstroke Diesel F250 uses the same pump for the front hubs and HVAC system. This pump is available on Rockauto for about $45. You could use one for the vacuum source for the cruise, isolate the cruise's vacuum from the car's so the HVAC in the car doesn't deplete the cruise's vacuum. Wire the pump to come on when the cruise stalk is put to "on". Cheaper than other solutions as long as the basic system is intact and functioning.

Thanks ihatebarking dogs- that's EXACTLY the info I was looking for! I have looked at the wiring diagrams and I figured it could be done but the biggest question I had was about the signal from the vss I suspected there might be a difference but I didn't know

May 6, 2018 | 10:29 AM

wishitwascamaro

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I took the cruise actuator apart it comes apart easily but the windings are very delicate you have to be extremely careful. There are 3 O-rings inside and I replaced 2 of them, the 3rd one is a non standard oval shaped o-ring so I coated it with a small amount of rtv- put it back together and it works great!