I have a 6 cylinder 2001 Chevy Sliverado. My check engine light came on about a week ago. So I took it down to autozone and had them tell me what my OBD was trying to say. My OBD said that I had a misfire in Cylinder number 5. OK, it has 40,000 miles, so I figure it's overdue for a spark change. While I'm at it, I changed the wires too. Well.....that didn't work. My check engine light is still on, I'm still getting vibrations when I accelerate, idle, and decelerate. So I ask you wise ones, what else could be causing my engine to misfire. I just ordered a Chilton manual, so hopefully I will be able to fix it myself, as I have yet to find a mechanic around here I trust. Thanks in advance guys.

alot of things can make the engine misfire...timing....is one of them....check the cap and rotor....check the plugs(proper gap)....check the wires are in the proper order and arent tied around eachother or magnetic flux can cause the wire to spark or jump Also get a timing light and check the timing itself.

2001 , bet its fuel injected with a injector pluging up.

V-6 then it's probably a 4.3L Vortec, in which case it has single point fuel injection.

GM ditched the cap & rotor game on their V6's a long time ago, and the timing is electronically controlled - so no more timing lights are needed... it either works or not anymore. And today's newer engines are designed to not 'need' spark plugs out to 100,000 miles (yeah, right - I inspect and change mine every 30,000 anyway).

One of the first places to look, is the coil pack that handles that particular cylinder. Your spark plug wires should terminate either into a single spark box, or a bank of 3 coil packs - 2 wires to a single pack. I'll suggest this: take a big screwdriver, and using the butt of the handle, tap the top of the coil pack a couple of times while the engine is not running - and don't be a puss about it (don't split the plastic or anything though). Then start it and see what happens... if the problem smooths out, then you'll be needing a new coil pack.

Another very likely candidate is the 'cam position sensor.' If this sensor is going bad or getting lazy, it can and will affect the timing of your engine, and in this case, the #5 is the one that's bearing the brunt of the bad timing.

Now, the bad thing it could be is a leaking head gasket, burnt valve, or bad valve seat. Leaking compression can act like bad timing as it will report the weakness to the computer as well.

You won't know for sure if you have 'TBI - Throttle Body Injection' (or Single Point as AceHigh puts it ) or 'MPI - Multi-Port Injection' unless you look under the hood. If you see two tubes (fuel rails) running on either side of the throttle body (in the center of the intake, where the air intake hose runs into). MPI will have 3 injectors along the fuel rail on either side plugged strait into the intake manifold with a corresponding wiring harness. TBI will use the Throttle Body for fuel distribution - much like the old carburetors, except with a pair of injectors instead of 'jets' and an accelerator pump.

Either way, I agree to try some injector cleaner first. You can try putting the stuff into your gas tank and hope for the best, or you can have it professionally done (where they tap into your fuel system with the injector cleaner directly) which will run around $60 or more, depending on who does it.

My bet is on one of the coil packs or the cam position sensor. But dirty injectors can do it too.

Good luck and let us know what you find out.

Ah! For the good old days, clean the points with a dollar bill, set them with a dime, and drive on. Of course even that wasn't needed if you did regular service.