My '94 626 has an idling problem. With the clutch in the engine revs between 800-2000 rpm. The engine changes idle speed a few times a minute. I had a mechanic look at the engine and he sprayed something near the back passenger side of the engine and it made the idle rev up. He said that it was probably a head gasket leak. Anyone have any input on what this problem is and/or how to fix it? The engine has 192,000 miles. I was thinking about using some RTV silicone to try to plug up any leaks there might be in the head gasket. Any help would be much appreciated. Thanks.

 

It probably has a vacuum leak, not a head gasket leak. The guy was just trying to get you to spend big money. You will have to find the hose or fitting that is leaking to solve the problem. There is probably a small vacuum hose that is cracked or something. RTV will not fix a head gasket.