91 Civic 1.6 Si idle problem/gas smell in cabin

SLICK26

MEMBER
1991 ALL OTHER MAKES ALL OTHER MODELS

I just got a 91 Civic Si from my brother for free (great deal huh?). It has 216, xxx miles on it and still running strong! But it has an idle problem after it warms up and if sitting at a stoplight or fast food drive-thru it starts to smell like gas, or possibly exhaust, in the cabin really bad. It gets to the point, if I have to sit there really long, that I have to open all the windows and sun roof, and sometimes that doesnt even help. It starts burning my throat from having to breathe it. Which obviously is not good.

The car is otherwise in really good shape, besides some minor things that need to be dealt with.
My brother did mention he thought it was time for a new cat converter. I'm not saying he's wrong, but it seems to me there's something else going on here, as well as possibly a bad cat.

The idling problem starts up after the car is at normal operating temp, not while its warming up. So once it is completely warmed up, it bobs up and down from about 1,000 rpm to anywhere from 1500-2000 rpm. Back and forth, up and down. Constantly. Then the gas/exhaust smells starts. It does not effect the way the car drives at all. Just while idling. Once the car is moving, its fine and the smell starts to go away, although not completely.

Give me all you got, I want this car to last because its currently pulling down 35-40 mpg for me! Thanks!

2 Replies

BRUCE HUNT

MECHANIC
3,754 POSTS

You could have cat going out but I would start with an exhaust inspection. Get the car up on ramps, one end at a time is fine and look at the system. Then look and feel for leaks with the engine running.

The fuel smell, raw fuel, is probably coming from a leaking injector. You can purchase new orings for the injectors and that might help. They are very easy to replace yourself.

The surging of the engine is associated with one of a couple of things. You very possibly have vacuum leak and it could be from a vacuum hose, intake manifold, intake manifold gasket, or a pcv valve. The coolant could be low and have air in the system. Purge the air from the bleeder located on the top radiator hose near the head.

Start there and let us know how it transpires.