Jim Grant's Tech Tips
'98 Ford Contour, Timing Belt Help
Q: I own a 98 Ford Contour SE with a 2.0-liter engine. I changed the timing belt and I cannot get the exhaust camshaft to set correctly. The engine starts good and then runs rough after a few seconds. I checked the compression and it has about 150 PSI in each cylinder. Any ideas on whats going wrong?
A: I am willing to bet coffee that the exhaust camshafts gear on your engine looked really different. Ill bet a second cup of coffee that you rotated the engine backwards to get the timing marks lined up before you took the timing belt off. That is where your trouble began. Todays engines are smaller, run remarkably clean and make horse power that was only a dream 20 years ago. To make this happen it takes technology and it is that technology that has bitten you in the back-end. The exhaust camshaft on your engine is computer controlled. This system is called Variable Camshaft Timing (VTC). Being able to vary the timing of the camshaft allows the engineers to maximize the performance of the engine at different RPMs and engine load. VTC systems are becoming commonplace on many vehicles. So how can you have a problem with a VTC system just changing a timing belt? Its easy! How do you solve that problem? Thats where the challenge lays. The VCT system on your vehicle can change cam timing by about 30 degrees. How does the computer do that? Inside that strange looking camshaft gear is a hydraulic piston that pushes against a spring. In between the two is kind of a spiral gear and all of this is inside of the camshaft gear. The computer applies engine oil pressure to the piston and the piston pushes against the spiral gear and the spring. This action causes the camshaft gear position to change in relationship to the camshaft. The computer in the mean time monitors the change via a sensor that reports camshaft position to the computer. It is the battle between the spring tension and the hydraulic piston that changes camshaft timing. The greater the amount of oil pressure the greater the change. When the computer removes oil pressure, the spring pushes back. So, while youre driving down the highway the computer is making adjustments to the camshaft timing. When you rotated the engine backwards you rotated the camshaft gear against the spring. When you installed the timing belt, even though the timing marks lined up, the exhaust camshaft was out of time. My suggestion to you? Purchase the information necessary to understand and correctly repair your vehicle or take it to a technician that is familiar with the VCT system on your vehicle.