2002 chevy tahoe cylinder 8 misfiring

Hello,
Your question lists codes p305p, and p305, which are not valid codes. Did you mean P0305? This is a diagnostic code referring to a misfire on cylinder #5. It looks like you've replaced parts that could be causing a misfire, but did not fix the problem.

A simple check to verify your misfire is not being caused by an ignition coil (the 4.8 liter engine has a coil-near-plug system, with one coil for each spark plug) is to swap the suspect coil (cylinder #5) with a coil from a different cylinder on your engine.

Cylinder #5 is the third one back from the front of the engine on the driver side of the engine. After you swap coils between a good cylinder and #5 cylinder, clear the codes and see if the misfire followed the coil- if a misfire code sets on the cylinder you moved the cylinder #5 coil to, you know the coil has a problem. That will at least help you rule out the remainder of the ignition system.

You are getting oil in the cylinder and that is fouling your plugs. I would guess your piston rings are bad letting oil up into the combustion chamber or it is leaking down from the head through the valve guides. Good luck

code P0303 is a misfire code for cylinder # 3, Possible spark plug, wire/coil or injector problem. P0141, bank1 sensor2, is the upstream oxygen sensor, this code may have been set by the misfire of Cyl #3, the lean condition is being cause by the misfire. Fix the misfire and clear the codes and P0141 should not return. If the vehicle is equipped with Coil over plug system try swapping the coil with any one of the others, test drive and if the misfire code changes to another P0300 code ( P0301, P0302, P0304 etc...) the coil has failed and will need to be replaced.

I would have it scanned and check what cylinders are still misfiring. I would change the ignition coil for that cylinder and see if that fixes the
problem. If the misfire is still there...the PCM will likely need replacement.

Check your coil pack. Sounds like one or two need replacing.

p0308 is cylinder 8 missfire, it could be the plug on that cylinder,wire, or coil. also make sure the injector for that cylinder is ok!! have a good day!

sounds like spark plug coil is bad. had the same problem on my truck also. check wich cylinder is misfiring and replace the coil and maybe the plug also. if the plug looks good leave it. autozone can give you a read out. when checking the coil, if it has a rust color to it its bad and needs to be replaced. 02 z28

Misfire means you need spark plugs replaced. Or spark plug coils.

That's why the whole car starts shaking because its running basically on 3 cylinders and not 4 as supposed. There is no gas compression on the 3rd cylinder because once again the spark plug is "misfiring"

There also might be even a bigger problem which could be the distributor cap where the coils are connecting outside the engine.
once you fix the problem the check engine will turn off immediately

hope that helps.

could be a bad plug even know they are new one might be bad , first check in the dark for any arcing (blue sparks) coming from wires might be a split in one of the spark boots ,make sure on there good,also a chance you put wire to wrong cylinder

If you have coils and spark plugs then you don't have wires. From personal experience these car's misfire because of coils and BAD INJECTORS. If you replaces coils and sparks plugs you need to check injectors. Get a NOID light and check injectors pulse to make sure it good. First you must locate the cylinder that has the misfire/Missing,this can be done by using a computer/code scanner or if can be manually by disconnecting each coil and see when there is NO change in idling or shaking. What you are looking for is when you disconnect the Eugine should shake more and when you reconnect it would smooth en out. If any cylinder when disconnected the engine doesn't change that the one with the problem. Check again for spark and make sure it good. Then check that injector pulse plug off injector connector and connect it to NOID light you should get a constant flickering of NOID LIGHT. If you do then BINGO that injector is BAD. However I must say this test is on valued if you have performed a compression test on all cylinders to make sure there are no BAD/Burnted valves. This can be done with a compression guage remember the reading should NOT be more than 10PSI difference between all cylinders example of a normal reading is cylinder 1 170 psi cylinder 2 168 cylinder 3 172..... abnormal is cylinder 1 170 cylinder 2 85 cylinder 3 172 ...etc. I know this is alot of info but read through and follow these step and you'll be ASE certified by the end of this job. Good luck and thanks for using FIX YA