"Check Engine" Light Turns On When Driving Past 70

[ghosthunter]

I've been using an old '95 Lancer GLXi (itlog) from my dad's office for the past few days, and I've been bothered by the fact that the check engine light keeps turning on.

Upon closer observation, it happens whenever I go past ~70 kph, no matter how low I keep my revs (i.e. 5th at 1.8k rpm).

The light only vanishes when I turn the engine off. Even after starting the engine again, the light doesn't turn on, at least until I hit 70 kph again.

I've had my engine fluids checked (oil, brake, power steering, etc) and all where within normal levels. Temps were fine too.

I plan to have the car checked soon, but I'd like to hear the thoughts of seasoned troubleshooters on this case, just so I know what to expect when I send it over for repairs. Thanks!

Maybe it has to do with the air-fuel mixture? ... a clogged fuel filter or clogged fuel line can result in leaning out the fuel mixture in to the cylinders.

[JohnM]

A resident gearhead who owned two CBs (both turbo) said there's a sensor in the gauge assembly that sends a speed signal to the ECU. You might want to start there.

The crank angle sensor can also trip a CEL but it looks like it's not related.

[basti08]

Maybe it has to do with the air-fuel mixture? ... a clogged fuel filter or clogged fuel line can result in leaning out the fuel mixture in to the cylinders.

Dirty MAF/throttle body?