Question about 2003 GMC Envoy
Skipping shaking problems
You are misfiring. If you have Autozone (or similar) research your check engine light, they will come up with one or more of the following codes P0300, P0301, P0302, P0303, P0304 etc. etc.P0308. The P0300 code refers to "Random/Multiple misfires" whereas the other codes refer to that particular cylinder (last digit) misfire. The P0300 code sets when 2 or more cylinders misfire (can be the same 2 over and over, but it takes at least 2 cylinders to misifre to set that code. The others only take one misfire to set the code. Now that you know what is happening, here is how to fix....
Takes all to fire a cylinder (Fuel, Spark, Air & Timing) properly. If you have random or multiple misfires, it is likely something that is COMMON to all cylinders - like the air intake/throttle body area - throttle body can get carbon buildup and not open/close properly. Check the fuel pressure to the fuel rail(s), fuel filter clogged? When you turn your key to the "ON" position, do you hear the fuel pump turn on (whine) and then shut off? No whine, means no fuel pump. Check all fuses and fuse relays related to the fuel delivery system. Check the distributor cap/rotor for any signs of carbon tracking/arcing. Do you have good spark from coil? Check wiring for the Camshaft Position Sensor/Crankshaft position Sensor for timing issues. Finally, check compression on all cylinders. Need good compression for combustion to take place.
For a single cylinder (example Cylinder #2) - Easiest to check is spark. Pull the plug and look at it. Is it wet and smell like fuel? If so, then swap it with cylinder next to it. If the problem moved, then its the plug. If the misfire is still on Cylinder #2, then swap the plug wire (both ends). If the misfire is still on Cylinder #2, then swap the coil. (see where this is going?) If the plug is dry, then check the fuel injector for operation. Noid light tester or you can get a long screwdriver and stick one end on your ear and the other on the injector - it should make a steady, rhythmic clicking sound if it is functional when car is running. No sound? Replace. Is the plug oily? Check cylinder #2 for compression. No compression or little compression means either head gasket blown or bad/sticking valve (intake or exhaust) = big money to get fixed. Timing on one cylinder is hard to test without correct test tools. Timing is likely not a problem on a single cylinder misfire. Good luck.
Posted on Apr 22, 2014
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Posted on Jan 02, 2017
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