Troubleshooting the cruise control in a 94. Any electrical components?

[NEO]

Last year I started to get some problems with my cruise control. I thought it automagically should have fixed it self over the winter but strangely it didn't.

It's a sporadic error and sometimes it works just fine but sometimes it can't keep the pressure (...or is that vacuum) so that it slowly (sometimes quickly) looses speed. It's always a bit saggy when accelerating with the button on the lever and not as responsive as it used to be. Spontaneously it feels like there could be a leak on a hose or so but what I wonder is if there's anything electrical involved in the cruise control that could act up?

What problems have you guys had with your cruise controls and how have you fixed them? Any common sources of error? A few times the hose on the 'throttle control element' have came loose but it's properly seated this time around so that shouldn't be the bad guy here.

Thanks.

[Skull]

i would say change the O-rings in the release valves behind the pedals...

[A80Avant]

Actually, i had a similar problem until recently.
I was told that it may have been the vaccum item that connects to the throttle, and therefore got myself another one. Then i realised you dont need to do that. if you try to blow through that item from the nipple that connects to the pump, it should not loose any pressure. If it does, usually its easy to locate a small tear which can be fixed with some silicone glue or something.

Anyway, that item was fine and i too, was gradually loosing pressure, when the engine was cold it wouldnt engage, or when warm sometimes you'd engage at certain speed and then it would gradually loose that speed.

Turned out it was a pump failure. I installed a used pump i got off ebay and the problem disappeared immediately.

[S2central.net]

Electrically they are pretty simple indeed. Air leaks should be ruled out first.

[turbo20v]

1. check vacum hoses and switches on pedals for leaks
2. check/clean tempomat switch
3. replace/try with another know to work tempomat unit (ECU)

[NEO]

Thanks guys. I will look into this in the coming weeks. =)

[veneto rs2]

Then i realised you dont need to do that. if you try to blow through that item from the nipple that connects to the pump, it should not loose any pressure.

I agree with Vas!
This is the perfect way to check the system for airtight.
It might sounds not so "professional" but it was the only way also for me to find a leak on one of the vacuum switch.
Actually....... (don't get bad on me here guys! Just trying to help!) sucking and holding pressure with your tongue on the hose works even better....

Going on previous experience I can say that if you're gradually loosing/not holding/slow to regain, speed, it's not electric/electronic but vacuum that you need to check.

Stefano

[NEO]

Actually....... (don't get bad on me here guys! Just trying to help!) sucking and holding pressure with your tongue on the hose works even better....

Just doing what you told me! http://piclair.com/data/6d17b.jpg

So I have been looking at this today. I did use the hi-tech sucking methods described and I also used a battery to put power on the pump. I have came to the conclusion that there is a leak somewhere inside the car. Everything in the engine compartment (including the pump) is okay. I removed the hose going to the inside and plugged the t-section with my left hand thumb and applied power to the pump and then it held the vacuum. With the hose to the components inside the car connected it leaks. Also, when sucking or blowing into that hose it's apparent that there's a leak somewhere there.

...UNLESS... yes there is an unless here. Are we sure that the parts inside should be airtight in idle state? Or are there any valves on that that open and shut with power? Is there any way to test the components down at the pedals? I assume we are talking about the black connectors at the clutch and brake pedal as seen here? http://piclair.com/data/pd4wj.jpg

I will take another look at them but if someone know how to troubleshoot them, let me know.

Cheers

[mcandmar]

Easiest way to test is use a MightyVac or any other hand operated vacume pump. Just remove the hose from the pump, add vacume until you see the throttle body fully open then wait. It should be totally airtight, i would expect the pump to be open to vacume when off as a safety measure but the rest of the system should be airtight.

Only had leak once on mine and it was the rubber bellows that operates the throttle body, basically the rubber had gone porus but only showed up with a vacume test. Symptoms started with an inability to hold a steady speed, would slowly drop a few mph, then accelerate, over and over. Eventually it got so bad it would set, drop speed, and then the system would turn off again.

[Skull]

i would say change the O-rings in the release valves behind the pedals...

remove stock hose from the valves, put some other pipe on one valve, blow, must be airtight when pedals are not pressed.

a new valve is something like 20€ from the stealah...

[NEO]

It was the valve at the brake pedal. And you know what... Those puppies is actually serviceable so now it's repaired (...i hope). Write up and pictures in a few hours when it's all back together.

[NEO]

Mkay. So the repair of the ventilation valves are actually pretty easy. You can read a bit more about it over at irry.com where there are a few more pictures too. But the little ******* looks like this inside (just noticed that I put some of the parts in the wrong direction for that picture, but you get the point):



I'm fairly certain that mine failed due to dust and foreign stuffs that shouldn't be in it. So I did a thorough cleaning of it and especially of the black rubber gasket closest to the pin in the picture. After the cleaning and reassembly it seems to be as good as new, with the addition of some duct tape.