My 1991 Civic station wagon, 2WD, automaticjust failed the emission test of Houston, TX.

High speed (25mph)
HC 181 (147 standard)
CO 2.57 (0.82)

Low speed (15mph)
HC 176 (152)
CO 2.91 (0.85)

The car just had a complete tune up two months ago. The car is running fine, gas mileage is very good (32 city, 35 highway).

The only problem is the temperature gauge is always low. On cold days (~35F), the needle barely moves past the C(old) mark when the car is moving. When idle, it moves up to only at most 1/4 from the C mark.

What have been your past experiences? How did you fix this emission problem?

Thanks

 

are you pulling a cel?

 

No. No check engine light.

 

That's the problem, engine must be fully warmed up before the ECU will operate for best emissions. Your thermostat is probably stuck open.

 

So you think change the thermostat will help?

 

Naive question: Is the thermostat at the end of the lower radiator hose? Engine side of course. Or is it at the end of the upper one?

 

Thermostat is at the engine end of the lower hose. There's nothing in the fitting at the top of the engine that goes to the upper radiator hose. Yes you should change the thermostat and if that gets the temperature to be normal (about halfway up the gauge), test the emissions again.

 

Thank you, mk378. That solved the problem. It passed the emission test with flying colors!

High speed (25mph)
HC17 (147 standard)
CO0.16 (0.82)

Low speed (15mph)
HC 27 (152)
CO0.21 (0.85)

I will post another question about the A/C. May be you can help too.