Tip & How-To about Cadillac STS
First do a compression test on that cylinder to verify there is no internal engine problems and compression on the misfiring cylinders is the sameas the other cylinders. If compression is good verify spark on that cylinder is as good as the spark on the other cylinders if not replace the spark plug and wire, if spark is still weak replace coil. If problem is still no or weak spark then you have a wiring problem on that cylinder. If spark is good use a LED testlight to verify the circuit has good power and ground pulsating on the injector circuit, if not you have a wiring problem if the circuit is working like it should replace the injector. If everything is good up to this point you likely have a leaking intake manifold gasket.
Posted by edwin187 on
Mar 10, 2015 | Cars & Trucks
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