What is normal idling
04-27-2002, 12:07 AM
#1
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Join Date: Mar 2002
Location: Columbus Ohio
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What is normal idling
I recently purchased a 87 951 with 50,000 miles and know little about them. Do 951s idle smoothly or with a slight hesitation. My car recently underwent a major tuneup and seems to run great but has slight hesitations at idle. I have never owned a 951 and wondered if this slightly irregular idling is normal or not. It also has a slight tendency to want to stall when first started on a cold morning which quickly resolves, ? is this normal as well.
Best Wishes
Tom Lawson
Cols Ohio
red black 87
Best Wishes
Tom Lawson
Cols Ohio
red black 87
04-27-2002, 04:01 AM
#2
Race Director
Did this irregular idle only happen after your tune-up? If so, then you may have a mis-adjusted or bad idle-stabilizer valve.
When the car is fully warmed up and you're cruising towards a stoplight and step in the clutch and let go of the gas, does it drop a little below idle speed and pick back up again? If so, the idle-adjuster (bypass) screw in your throttle body is screwed in too far. That makes the idle-stabilizer compensate by supplying additional air, but its slow response time makes the idle drop and pick back up. You want to open the bypass screw so that it is providing 100% of the idle air, thus taking the idle-stabilizer completely out of the loop (only needed on cold starts).
If however, you're also getting an irregular or rythmic cycling idle, then you've got a vacuum leak after the throttle body some place. Most likely in the hoses underneath the intake manifold. These get hard with age and it's easy to crack one when you're fiddling around with the ignition wires.
When the car is fully warmed up and you're cruising towards a stoplight and step in the clutch and let go of the gas, does it drop a little below idle speed and pick back up again? If so, the idle-adjuster (bypass) screw in your throttle body is screwed in too far. That makes the idle-stabilizer compensate by supplying additional air, but its slow response time makes the idle drop and pick back up. You want to open the bypass screw so that it is providing 100% of the idle air, thus taking the idle-stabilizer completely out of the loop (only needed on cold starts).
If however, you're also getting an irregular or rythmic cycling idle, then you've got a vacuum leak after the throttle body some place. Most likely in the hoses underneath the intake manifold. These get hard with age and it's easy to crack one when you're fiddling around with the ignition wires.