Air leak gran
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Reason why its not there on a cold start up is due to the enrichment on the efi.
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basically, theres a shed load of fuel entering and the idle control valve when its wide open.
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the engines is expecting an extra flow of air and fuels.
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When the engine gets hot, the fuelling is majorly reduced.
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when an air leak occurs, its draws it in from there instead of the throttle body
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so the engine rises in rpm.
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but theres not enough fuel and confusion occurs as the throttle is closed
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( throttle position sensor
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) and hence your surging engine idle.
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Suggest replacing the gasket for the idle control valve for a start
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( as its been off
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), then throttle body, then the intake manifolds
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!!
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Basically all the gaskets on the inlet manifold.
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Its difficult to tell if theres a leak
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( mechanical view
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)
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- where air is being pulled through.
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It only needs to be a little bit of grit on the surface when bolting up to draw the air in to upset the idling.
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Hence
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- change all the intake manifold gaskets
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- check
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/ inspect surfaces
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/ casing for cracks etc.
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That should resolve the problem.
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the idle contol valve has been changed
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Was this changed for a new one or for a used one that may have been caked up
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??? I've cleaned a few up where they've been stuck open, so cold idling is good as the valves wide open, but then when warmed up, the valves still jarred open
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= excessive air being drawn in which will give you that erratic idling.
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So recap
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:
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Inspect idle control valve first
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( strip off throttle body and inspect valve actually moves and not seized
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)
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Change throttle body gasket whilst your there, or thin coating of instant gasket will seal it up.
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All the above and still no resolution, budget for changing all the intake manifold gaskets.
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Have you ever unbolted that top flange
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( curiosity
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?
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) which is part of the plenum on the intake manifold.
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the bit with the bolts
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???
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( just in front of the engine lid anchor point
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!!
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you could try doing that one yourself, unbolt all the nuts and bolts, get some instant gasket, thin coating around the gasket and bolt it back down
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I'm 99% sure its an intake drawing too much air issue.
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all mechanical, not electronic.
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The engines generally don't have a problem like that unless its been disturbed
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- like idle control valve removal etc.
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Keep smiling.
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