2009 Civic 1.8L rough idle with the AC on

Messages
6,170
Location
North Coast
Daughters 2009 Civic idles rough with the AC on. Now at 85k. What could be the cause and remedy? It just started doing this recently.
 
Messages
16,239
Location
N.H, U.S.A.
How is power, idle quality, and fuel mileage with the AC OFF? You cold have lost some atomization on one cyl due to carbon on intake valve or poor injector spray pattern on one causing poor cyl balance. You coul load the engine up against the brake and pull off one injector conn at a time to look ad power drop. This will point to a weak cyl. Could be a dicey proposition if inexperienced. Dont pull plug wires. Do you currently see a MIL lit for misfire? or stored code?
 
Messages
8,307
Location
Grand Rapids, MI
I've always noticed more engine vibration and roughness when having the A/C on at idle in my Acura. My girlfriend said her low mileage '01 Civic does the same thing. Hopefully you find out what the issue is, as I'd love to know.
 
Messages
2,362
Location
Texas
Hondas are known for having motor mounts go bad when they get older. If this is the case, the car probably isn't idling rougher, you are just FEELING it more. At about 5 years old (and older) and starting at about 85k miles are typically when this problem will begin to appear. Have a mechanic that is familiar with this problem check it for you, it should take him less than 5 minutes to diagnose on the service drive. Because they use captive motor mounts it is not a safety issue, and you can continue to drive the car with bad motor mounts, but it is very annoying, and it will get worse. Mazda3s and Ford Focuses also have this problem. They must get their motor mounts from the same vendor.
 
Last edited:
Messages
484
Location
IL
Originally Posted By: wag123
Hondas are known for having motor mounts go bad when they get older. If this is the case, the car probably isn't idling rougher, you are just FEELING it more. At about 5 years old (and older) and starting at about 85k miles are typically when this problem will begin to appear. Have a mechanic that is familiar with this problem check it for you, it should take him less than 5 minutes to diagnose on the service drive. Because they use captive motor mounts it is not a safety issue, and you can continue to drive the car with bad motor mounts, but it is very annoying, and it will get worse. Mazda3s and Ford Focuses also have this problem. They must get their motor mounts from the same vendor.
Same thing, I believe, that is happening in my '95 Camry. If no harm, I'll live with it.
 
Last edited:
Messages
2,362
Location
Texas
Originally Posted By: lukejo
Same thing, I believe, that is happening in my '95 Camry. If no harm, I'll live with it.
Toyotas are not known to have motor mount problems, but, after almost 20 years of use the rubber in ANY manufacturer's motor mounts will have deteriorated/aged/hardened to the point where the engine will be transmitting considerably more vibration into the body structure than it would if they were new and subtle. I'm with you, on a car that old I would probably leave them alone.
 
Top