Idle smoothness and clutch; what/is there a link?

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Hello, all. As many of you might be aware, the 92 Civic I drive(see sig), has a clutch that is on the way out. Currently, I'm working to get in a position to handle this. I do have an interest in learning more about what is going on with this car. I feel like the engine and transmission are working just fine, I still get 40 MPG and it only consumes about 1 quart every 3,000 miles or so now approaching 257,000 miles. The issue is that the idle has become more 'uneven' and to the point of lugging/feeling as if the engine is choking/sputtering occasionally at idle, especially if there is added electrical load such as when the A/C on or cooling fans cutting on. This happens more often after driving the car hard or idling with the engine hot. Could a worn out clutch affect idle in any way? The Input Shaft Bearing makes noise at idle and needs replacement when the clutch kit is put in, if that could contribute to things here. The 'idle speed' is supposed to be set for life on this car, the throttle cable is fine. There is a small leak beginning at the clutch pedal as the master cylinder for the clutch hydraulics is beginning to fail internally. It's the only things I 'know' about on the vehicle. If any other maintenance related questions are needed, please ask. Trying to track down the symptoms for this car and whether it's all in my head or not. grin2
 
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JRed

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Your idle roughness is probably either your idle air control valve, fast idle valve, EGR valve, vacuum leak, or something of that manner. Is the vehicle's "hot idle" proper? Not too slow?
 
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ltslimjim

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^It seems like the hot idle is too slow...at times. Almost as if the oil pressure is too low? The IACV/EACV was cleaned up over a year ago to the fix the 'fluctuating' idle issue when I first got the car. The EGR valve functions, the ports were cleaned a year ago as well. Is it possible there was more gunk/soot that has re-clogged the EGR system? It would be worth it to try looking for a vacuum leak. I could spray various hoses along the Intake Manifold to listen for any idle adjustments. I have not checked the Fast Idle Valve, though, and I've heard those can get too loose.
 
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The roughness is most likely engine problems. All sort of things to go wrong here! Want a long list? But a bad input bearing could be severe enough to cause roughness. Are you referring to the pilot bearing or tranny input bearing?
 

ltslimjim

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Originally Posted By: mechtech2
The roughness is most likely engine problems. All sort of things to go wrong here! Want a long list? But a bad input bearing could be severe enough to cause roughness. Are you referring to the pilot bearing or tranny input bearing?
Input Shaft Bearing tranny side. I have yet to have a leakdown test performed. I did have the valve lash adjustment made 1 year ago by a mechanic. I wonder if it was done too tight OR since it probably was the first time it has had a valve adjustment in YEARS that it could be off again?
Originally Posted By: spasm3
exhaust valves only last so long, you might be leaking enough at low rpms to affect idle. a compression test might tell you.
^This has ran through my head. I suppose I'll just have another compression or leakdown test performed when I have the clutch kit put in/ISB replaced.
 
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Originally Posted By: ltslimjim
^It seems like the hot idle is too slow... The EGR valve functions, the ports were cleaned a year ago as well. Is it possible there was more gunk/soot that has re-clogged the EGR system?
Did you clean the EGR valve itself, and check that it is closing properly? I had a problem similar to yours on a '94 Saturn, and it turned out that the EGR was sticking open just enough to affect the idle. That was a replacement valve. Before, the ports were plugged solid and the OEM valve had basically disintegrated inside. With the ports plugged, it ran fine but threw a code.
 
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Originally Posted By: ltslimjim
Could a worn out clutch affect idle in any way?
It could... but I think you'd notice other things. A severely warped clutch disk could drag, but you'd notice the gears being hard to engage, grinding, or the car trying to creep when in gear and with the clutch engaged. Same thing if the clutch cylinder were leaking down- you'd get the same symptoms because the clutch would be engaging as the pressure leaked away and the car would creep in gear, gears would refuse to engage or grind, etc. Next time it does this, pop the shifter into neutral. If the idle behavior changes, its clutch related, if not then you've got one of the issues other people have brought up. My bet is on the idle air control system.
 

ltslimjim

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I'm starting to hear some 'roughness' in one of the bearings on the drive-belt system. It's either the harmonic-balancer or the pulley on the AC compressor. Someone mentioned 'thrust bearings' leading to engine stalling; is that related to the Input Shaft bearing at all? The car's torque is is down, a lot of power lost with the worn clutch, and its causing the driving feel to be erratic.
 
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