Contour Enthusiasts Group Archives Forums General Troubleshooting Rough cold start

When I first start the engine, for 1st 30-60 sec the engine runs rough and then smoothens out. There is a distinct change in the sound of the engine when it smoothens. The change from running rough to smooth is almost instantaneous. My car is Contour 4 cylinder ztec (1995) with 135,000 km. I don't know if the 2 are related, but I also find the engine running slightly hotter...The needle is at "A" in "NORMAL" range.

When the engine is first started it is in open-loop mode. This ignores correction data from the O2's until they warm up to operating temperature.

You have a mixture problem which is mostly corrected when running closed-loop. Clean the MAF and check for air leaks. Common air leaks are vacuum lines including the hose on the PCV valve, the fresh air line from the valve cover to the intake tube, an open oil cap or dipstick, connections between parts of the induction system...

Timing belt and fuel pressure may be causing this.

Poor spark and bad engine mounts will make the roughness worse.

Not to hijack the post or anything, but when someone shuts my car off while im right by the engine bay with the hood up. I hear a dissipating hissing noise coming from the left side of the UIM. This sunday I am planning to take my manifolds off and cleaning them. Do you think cleaned up manifolds and new gaskets could solve the problem that I think might be a gasket leak?

The only things I can think of that would hiss after the engineis off are the A/C, residual pressure in a cylinder, or a bad one way valve between the UIM and the vacuum resivoir. The vacuum in the manifold dissapates very quickly and you won't hear it. Still, it's a good thing to do for a 96.