Cruise control slows down when set

[craigmcd]

Howdy.

We have a 1999 Legacy Outback in overall good working order (it has a rebuilt motor less than 3 years old which runs great).

 

When I depress the lever and engage the cruise control - the car goes into cruise control, but slows 4 to 6 miles per hour, depending on the overall speed. It will then hold that speed just fine. To cruise at 65 mph, I would have to engage it at 70 or 71 to allow for the slow down. It is bothersome to say the least.

 

Is this going to be a computer problem, electrical, or more mechanical - like a bad CC unit in the steering column ? Any other ideas would be great. Is this something a garage can electronically diagnose?

 

Thanks, Craig

[Fairtax4me]

That's an odd one for sure.

The cruise was vacuum operated on most of the cars from that era. There is a small vacuum pump on the passenger strut tower kinda behind the AC drier canister. This will have a vacuum hose leading to a steel line that runs across the firewall over to the cruise actuator on the drivers side near the brake master cylinder. Check the hoses that lead to/from the pump and the actuator for cracks/splits and loose fitting.

Also check the adjustment of the cruise cable at the throttle lever. Compare the amount of slack in the cable with the amount in the throttle cable. There should not be a lot of slack in either, but if the cruise cable has more slack adjust the lock nuts to take out some of the slack and see if it helps.

[craigmcd]

I had not thought of vacuum hoses, that is a great suggestion. I will check it out when I get a chance. Thanks Craig

[craigmcd]

I had a chance to work on the Subi over the weekend. Following your suggestions, I checked the throttle cables, which were fine. Next I followed the vacuum tubes, and low and behold found one with a split end which had fallen off. I trimmed it shorter and reconnected it. That seems to have fixed the cruise control. What puzzles me is how it was working at all.

 

I was also working on an EGR check engine light which came on a few days ago. I found that the vacuum hose from the valve to the manifold was missing the entire center portion. Not loose, or disconnected - a 3" section in the center of the hose was MIA. I replaced that, and a couple others which seemed about the same age. I think the EGR problem is corrected, but need to get the dashboard indicator to shut off. I think it will automatically - here's hoping.

[ivans imports]

try addjusting the cable coming from vacume pot and check its vacume lines

[Fairtax4me]

CEL can be reset by disconnecting the battery for a few minutes, but this resets everything else as well.

Or you can go to an auto parts store and have them scan the code and clear it. (I've heard that some will no longer erase codes due to liability reasons).

 

Or you can get your own code scanner off eBay for about $20 and read and erase codes to your hearts content. You could spend a bit more and get one that reads freeze frame and live data for better diagnostic capabilities.

[craigmcd]

When the Check Engine light came on someone suggested going to Autozone for a free reader test. I did that to find out something was amiss with the EGR system. He mentioned that Autozone will not clear out the codes anymore. I actually appreciate that. It helps people buying used cars.

 

When we bought our 2005 Subi Outback (the sweet VDC Limited H6) it was running fine. Then about 2 weeks into our ownership the engine light came on. It took nearly $1300 to get it to go permanently off. So, I can see why they would not want to turn those off in the parking lot of auto parts stores. By the way, it has been two + years since the 2005 was repaired at the dealer, and it has run great ever since, with no problems. I do recommend Ehrlich Subaru in Greeley, CO (I hope we can do that in the forums) -  but they did what they promised at the price they quoted, even though it took them nearly 2 weeks to figure it out. They also provided a nice new loaner while they had our car.