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Cold start surging

howie149

By howie149
in 911, 912 Series

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howie149 Member

howie149

Posted
Posted

Hey folks. I just bought a 1989 911 and am a noob. When I cold start the car the engine surges in between about 1250 RPM to 2500 for about a minute. Then it settles into a relatively smooth idle of 1000 or so. My question is: Is this a problem and if so what might it be? What should I replace? I've changed out the O2 sensor and replaced the vacuum hoses that I thought were cracked. (although the ones near the gas tank need to be replaced still) I made sure all of the other vacuum hoses were still attached and tight. What gives? Thanks again.

wvicary Member

wvicary

Posted
Posted

There are a few things that can cause this fault and the first thing is the have the intake system smoke tested for vacuum leaks. The air flow meter boot between the air meter and throttle body and throttle body and idle speed motor are common areas. Also inspect the fuel pressure regulator for a vacuum leak or passing fuel through into the intake manifold from the vacuum line.

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