The 2004-2008 Toyota Corolla and Matrix with the 1.8L 1ZZ 4-cylinder can throw a check engine light when it is cold, the code stored being P0171 – System too lean.  The tricky part with this malfunction is how difficult it is to catch acting up – by the time the auto mechanic has pulled the car inside for diagnostics, it’s warmed up and the problem disappears.

The most common cause of this is a failing intake manifold gasket that leaks when it is cold.  Your local Toyota shop can confirm this is the case by checking the data the car saves when it sets the check engine light.  In this freeze frame data you’ll be able to see the temperature of the intake air and the fuel ratio going into the engine – cold air temp combined with lots of extra fuel indicates a cold soak vacuum leak.  If the problem resolves once the car warms up you likely have this issue.  So how does Toyota recommend repairing the problem?  They updated the intake manifold gasket:

Intake Manifold Gasket

Above: updated intake manifold gasket

You can differentiate the old gasket from the new by the color – the original gasket was black, the new is orange.  As Eden Prairie and Chanhassen’s Toyota repair specialist we see this fairly often (we keep the Toyota OEM repair part in stock) and wanted to share our fix with those may not be as familiar!