Replaced an intake manifold gasket due to coolant leak. Two days later it started misfiring. Replaced the rotor and pick up coil, no difference. Any suggestions?
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2002 Chevrolet Blazer Question: Misfire
Answer #1patrick mannion from Greg Solow's Engine Room, May 25, 2009, 12:41Master
I suspect the misfire may be due to an a vacuum hose having come off the intake manifold or the intake manifold gasket is leaking allowing air in past the gasket causing a cylinder to run lean. Has the Check Engine Light /Service Engine Soon Light come on? If so it will probably identify the cylinder that is misfiring if a scan tool is plugged int othe diagnostic socket under the dash. If indeed it is a misfire caused by a vacuum leak a garage would locate the "leak" by sealing off the intake air from the air filter housing and using a machine that generates non-flamable smoke . A hose is placed in to the intake manifold and the smoke that then is pumped into the engine will locate the leak as you will be able to see where it is leaking from. Another test to locate a vacuum leak is to use propane with the engine running. the garage will move a tube connected to a propane bottle around the intake manifold and when they locate the leak the engine will speed up as you have introduced fuel to a cylinder that had been running lean due to the vacuum leak.