Knock sensor
 

I have a 95 CX hatch. I've owned it from 92,000km to 275,000km and it's now starting an intermitent knock. I did a search in this section and found five posts that contain knock sensor, so I am assuming that the Civic does have one of these. It does not seem that a faulty knock sensor is the likely problem since no has posted with this problem. Does anyone have any ideas? I'm going to do a search on how to check ECU codes and I'll review my Haines manual tonight.

RE: Knock sensor
 

Are you throwing a code? Have you tried premium (higher octane) fuel? Older motors just need premium somtimes.

Only OBD-2 Civics have a knock sensor.

RE: Knock sensor
 

how long do you let your car warm up, and does it go away after it you drive it for a while

RE: Knock sensor
 

If it needs premium, it might have some carbon buildup on the combustion chamber. To fix this, i think there is some stuff u spray into the throttle that will eat the carbon away. Don't know much about the stuff.

RE: Knock sensor
 

I've never actually checked for problem codes on a civic yet. I thought that codes would only be available if the check engine light came on; which it has not.
It never needed premium before, but maybe I'll try it and see what happens. I would think that as an engine gets older and the compression goes down it would be less likely to predetonate.
I don't know what OBD-2 Civics are. Are they from 1996 onward? I also have a 98.

The car is my wifes'. Warm up! Hell no; she has it in gear before the starter has disengaged the ring gear. I asked her about temperature and she said that the knocking stops after the car warms up. This does make me think that maybe it's not spark knock, but a worn bearing or excessive clearance that closes up as the engine warms up. I'll get her to try a tank of premium. If the knock doesn't go away, I'll figure it's not spark knock. Do you figure this is a good assumption?

Does anyone know what this stuff might be? When I was younger in auto shop, I remember hearing that you could pour a small stream of water into your carb while it was running and that the water would blast away carbon deposits as it vapourized. I tried it with my little Chevy S-10 Blazer that I had at the time. It never had any spark knock problems in the first place but it didn't stall the engine or seem to cause any problems. I don't know if it did anything.

Thanks for all the suggestons.

RE: Knock sensor
 

Well I got the wife to try a tank of premium and the spark knock has gone away. But why does it only knock when the engine's cold. It seems to be totally opposite to what I would think would happen. From what I understand, spark knock is the air fuel mixture igniting before the piston reaches top dead center. This could be caused by carbon deposits in the combustion chamber glowing red and preigniting the fuel mixture or the timing being too far advanced. What doesn't make sense is why does it happen when the engine is cold but disappears when it warms up.

Anyone have any ideas?

I'm going to borrow my dad's timing light and check the timing.

RE: Knock sensor
 

i dunno if i would pour water into a modern engine. it might not like it. but your right, it usually will knock when its hott, going up a hill under a load.
but if higher octane fixes the problem, then it is spark knock. do you have the right heat range of plugs?