I have a 2002 Chevy Silverado 2500HD with 6.0 V8 engine that is idling rough. On dianostics it showed cylinder 2 misfire. Plugs, wires, fuel filter, and #2 cylinder coil pack have been replaced. Truck is still rough while at an idle and no codes show up on dianostics now. Any ideas where to go next? Also, truck runs worse after it has cooled off like overnight or after not running for 2 hours or more.

Misfire in cylinder #6. Could be bad spark plug, spark plug wire, cop coil, bad intake/exhaust valve, clogged fuel injector or piston/cylinder problem. What's the year, make, model, engine and have you been following the recommended maintenance schedule for new plugs?

It's not those. It's the coil pack electrical plug. Pull the plug and use a hair dryer to dry it and the coil pack. Never use a power washer on the engine. The weather pack seals can't take that kind of pressure.

Lets start at the beginning. Did anyone check fuel pressure before and after replacing the pump ?
Has anyone checked the fuel pressure regulator and the injector spider ? The 4.3w engine uses a spider with one injector that supplies all 6 cylinders. And it runs at 65psi or more.

misfires are more from problem injectors, low fuel pressure or injector wiring than from plugs
have a fuel pressure test done to check for problem pressure regulator , problem fuel pump , blocked m/dirty filter
one other area of concern is the EVAP system where the purge valve doesn't vent the tank properly and causes low fuel flow rates

You may need to check the engine timing, that would be the first thing,, 4.3 is also bad about leakes in the fuel lines that are under the intake manifold. this is part of the fuel injection system, it will cause it to rough idle, but will accelerate fine, but when come to stop, will have a rough idle.

Try swapping the injector on that cylinder with the one next to it and see if the misfire changes to the other cylinder.If it does then you have a plugged or bad injector.It it still stays on that same cylinder then check compression on the number 6 cylinder.Let me know what you find out.Good luck.

Hi, the 4.3 liters have an injection system on them that can leak and will show up as a misfire. it is common but elusive to find. you might consider taking the van to a repair shop to have the problem diagnosed and go on from there.

Black smoke could mean it is running rich, have a scan done, it is probably an engine misfire code and it will tell you which cylinder is misfiring. the last digit is the cylinder, unless it says random missfire, It may be time for a good tune up and don't forget the fuel injection system, Clean out the intake and do an induction cleaning on the injectors.

i have a 2001 chevy z-71 5.3L. I keep getting a random/multiple misfire code for cylinder 1 . I have replaced plugs, wires, coil pack(only on #1 cylinder)., and fuel pump. I still keep getting the cylinder 1 misfire code. I put truck on a scanner and watched the cylinders. # 1 misfires at idle but quickly stops misfiring at around 1000 rpms. you can here the engine miss at idle but truck runs great on road . anyone else ever had this problem?

Disconnect the battery completely, try turning the key with the battery disconnected. Put the battery back together. The check engine light should be off now..