I have a 97 Civic HX. My civic's idle is perfectly fine when in neutral, but when I drive, I feel a constant light thrusting. When I stop at a light the thrusting gets bad. The idle goes from 1200 to 0 back and forth, if I hold the brake too weak I leap forward. Now Im used to putting it in neutral at red lights. On some rare occasions, the idle is fine and nothing happens throughout a day of driving. I don't get it. Has anyone else had this problem?

 

is this a automatic?

sounds really odd....
gotta be some small sensor or something messing up, do you have the CEL light on the dash?

 

My first suggestion would be to check all sensors, be sure that they are clean. Use some throttle body cleaner make sure your TB is clean

also make sure there is nothing around the throttle body that could be opening it by pressing on the part that the gas peddle goes to (no idea what its called)

its sounds more like the something with the TB than the trasmission. but i may be wrong.

also unplug the IAVC and see what it idles at.

 

Ok got the car back from mechanic. Cleaned the throttle. Check engine light was on so long before i had it that the bulb burnt out. I am told that the egr valve is clogged and the car is running lean. Im paying almost 100 bucks an hour of labor for them to look for problems, its getting ridiculous.

They are telling me that in order to fix the surging idle, I would have to replace the transmission to cancel that out as a factor. Would a transmission make the idle do something like that?

 

well i dont think the tranny would make the engine surge.
i would get the engine trouble codes and fix those first. and see what they does. other than that i would deal with it if its not that bad....

replacing a automatic tranny aint cheap!
it might not even be a problem infact.... could just be the normal pull on the tranny, lets face it if ya let off the brake its gonna have enough pressure to make the car want to go forwards.... it could just be your motor is running crappy from the bad sensors that need to be replaced that its puting more of a strain on the driveline....

just fix that CEL light bulb and get the codes and fix those error codes. hell the car already needs them obviously! then if the problem is still there then worry about it more.