Rough Idle only when the A/C is on - Page 2

blakeclevenger · 11-17-2012, 11:12 PM

okay so I found out tonight that the idler pulley and belt tensioner really need to be changed. Hopefully each of these are creating enough drag that its lugging the engine down once the A/C comes on. The parts stores were closed tonight once I realized this, but tomorrow I will replace them and find out. From what I could tell, it seemed that the A/C bearing was in good condition. Thanks again for the help guys. I will keep you informed tomorrow.

***whynotthinkwhynot*** · 11-18-2012, 05:18 AM

That's possible.

Tell me, does your car idle higher in the morning after it's been sitting all night?

amc49 · 11-19-2012, 02:03 AM

Nope. If that were true the motor would be lugging with a/c off too. The pulley and tensioner are in use all the time.

I consider 'a/c on' lugging pretty much normal on higher mileage 4 cylinder cars, older motors do not have the idle rollover torque new ones do. From what I've seen the IAC bumpup in speed really is only enough to cover pretty close to new motors. Same issue shows when fan on or power steering is hit on limit. The IAC bumpup occurs, just not enough of it. Software issue. Engine too small. Put same exact a/c system on a V-8 and motor powers right through it because more torque at idle.

Now if vibrating dash when a/c on, look to your passenger side motor mount.

blakeclevenger · 11-24-2012, 02:07 PM

So after changing the idler pulley, and the tensioner pulley, the problem is solved. They weren't horrible, but they clearly weren't operating smoothing like pulleys should. This had solved the rough idle issue for me when the A/C is on. My theory is that the car didn't have the power under idle in its old age to handle both the A/C and the crappy pulleys without getting bogged down. Also in this process I gave it a tune up (plug wires and plugs). The car runs significantly better and has no idle issue.

Lesson learned: Dont over think it and rule out the simple stuff. Hopefully this thread helps others. Thanks to everyone in the community that chimed in and offered their advice and experience.

amc49 · 11-24-2012, 11:47 PM

A lot of it is fan coming on while a/c is on. That fan really jerks idle down when motor is older. May be one reason why OEM fan is engineered to come on at a later temperature than many think normal. At one time before I put in diagnostic LEDs to show when low and high fan and a/c clutch itself came on, I thought that low fan was not coming on properly. I installed a standalone adjustable fan control set to come on at 210 and back off at 190. That thing switched fan on so much during the summer it became very bothersome at traffic lights, the engine always seemed to be shuddering from the fan kick-in. I installed the LEDs and defeated the add-on control and went back to OEM fan on temp of 230 degrees, the problem quickly became much less noticeable since fan was coming on far fewer times.

PWGuy · 12-28-2012, 12:11 PM

Quote:

Originally Posted by blakeclevenger

So after changing the idler pulley, and the tensioner pulley, the problem is solved. They weren't horrible, but they clearly weren't operating smoothing like pulleys should. This had solved the rough idle issue for me when the A/C is on. My theory is that the car didn't have the power under idle in its old age to handle both the A/C and the crappy pulleys without getting bogged down. Also in this process I gave it a tune up (plug wires and plugs). The car runs significantly better and has no idle issue.

Lesson learned: Dont over think it and rule out the simple stuff. Hopefully this thread helps others. Thanks to everyone in the community that chimed in and offered their advice and experience.

To change both of these pulleys, did you have to remove the timing belt? Or are both of these pulleys on the accessory belt?