billy mild

My cruise doesn't seem to be working properly. When I engage the cruise it will be fine for one second then start to pulsate on and off, accerlate and slow, rinse and repeat. It never is smooth or holds the speed.

Could this be related to a vacuum leak or is this a cruise computer issue?

jgalfo

My guess would be a slow vacuum leak.

John

pcolt94

Most of the world runs right to the vacuum problems. The quick item that should be checked first is the 3 hose check valve for cracks or breaks. It is on the right side of the engine, on the top under the plastic cover. But if you’re A/C vents are working OK then it's probably going to be good.

But I can tell you from a lot of experience on these problems and helping people for years the most common problem turns out to be electrical. Specifically the cut off switch for the cruise which disengages to cruise when you press on the brake. This is a triple switch which does the cruise, brake light and TCC lock up. The part of the switch for the cruise develops high resistance on the contacts and causes these problems. The switch can be replaced, or disassembled and contacts usually cleaned.

The clutch pedal if a manual transmission has a switch on the pedal also for cutoff however it seems the switch on the brake pedal seems to cause the most problems.

Here is just one of my threads for reading.
https://www.corvetteforum.com/forums...-for-94-a.html

billy mild

I have ZR1 so it may be different. I wasn't sure if the cruise used Vacuum at all. I know some cars do and others don't. My old 944 Turbo did not use vacuum for the cruise. It used a little computer and servo motor to regulate the cruise speed. The Jeep I have however does use strictly vacuum to control speed.

I will be pulling the intake manifold to hopefully fix all the vacuum leaks this car could have. Where is the best place to buy those check valves?

pcolt94

Why are you pulling the intake?

Check valves can be bought at auto part stores, internet or EBay.

Even cars that use vacuum for the cruise still use electronics for the speed sensing, control and vacuum solenoids.

jake corvette

Quick and easy check - cheap too. Make sure the throttle cables are free and are not binding. If they are, try a cable luber - available at your nearest motorcycle shop. Replace the cable if it has a kink or has been bent.

Just some thoughts -

Get back with us with what you find out.

Jake -

ken4

My cruise would cut out for a while and then come back on. Did that for a few years and started looking around here on the forum before I started throwing money at it. Read your article and it looked like you knew what you were talking about (some do not). I replaced the switch and am finishing up my second year of a repaired cruise. Thanks for sharing!

65Z01

Do a carefyk check of the three control hoses where they slide over the plastic fittings.

You might put a vac gauge in series with the input hose from the balast tank.

RIPS

billy mild-Not sure if you've solved your problem yet. I just logged on this week to catch up on posts and saw yours. I've had a similar problem where the cc wouldn't hold speed and mine was caused by a slow vacuum leak due to a small hole in a line. Here's a link to a post where I helped another member who's cc had quit working and the pictures will help. Good luck.
https://www.corvetteforum.com/forums...post1586199928