SilverBullet:
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May (also) be a vacuum leak.
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???
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There may be a stored code that will point you to the correct location ......... MAF ......... IAS ....... whatever ......... if the check engine light came on
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Your story is almost exactly the same one that I experienced with a Ford 4.0 SOHC engine when faulty intake manifold o-rings would cause a vacuum leak (at cold start up) .....
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the engine would race when started ............. .the engine would stumble ............ and the check engine light would illuminate. The O2 sensor was replaced ....... this occurred another time ........... after the second time, they (finally) treated the problem and not the symptom ........ replaced the intake manifold o rings .......