My 1996 tahoe is giving me cylinder 2 misfire And runs ruff idle

Do a Cylinder Leak Down Test --to see if the valve are shot & leaking

You can also do an electronic cylinder contribution test

Then if the all seal, check the timing belt

After that check for vacuum leaks with evap smoke machine

Hi Yvonne, I'm glad to help!

The first step when you have a misfire is to see what is causing the misfire. Technicians always rules out mechanical failures before moving on too Electrical issues. What you need to do is check compression on cylinder 2 and see if its good. Remove the spark plug and test it with a compression tester. It should read somewhere around 150 PSI or more. Check it to cylinder 4 and make sure the reading are close they must be within 25 %. If the compression is GOOD then you'll need to move to the electrical checks. Here's how you rule out parts. It doesn't matter if you have plug wires or coil-on-plug. SWAP the parts from cylinder 2 to cylinder 4 and start the engine and if the misfire moves from 2 to 4 then you know its either the spark plug the spark plug wire or the coil pack if you have a coil instead of a plug wire. If the misfire does not move and stays in cylinder 2 then it could be an INJECTOR, WIRING ISSUES, COMPUTER DRIVER. As you see Yvonne it can be a lot of things that can cause a misfire. Hope this helps and have an awesome day Yvonne.

http://troubleshootmyvehicle.com/gm/3.8L/troubleshooting-misfire-codes-1

Hope this helps

A misfire alarm typically means the coil pack mounted above the sparkplug indicated in the misfire had gone defective.

To test it, swap the coil pack with another cylinder, and see if the misfire goes from #2 to the cylinder you put it on.

If the misfire continues to be on #2, then consider changing the sparkplugs.

I hope this helps.

P0300 random misfire, slight rough idle good , by the way your repair is good you dont want a identified misfire, Lets start by what it is not. Not a misposition sparkplug wire you would of gotten that cylinder code, as misfire, Oh try this got carburator cleaner? spray safely along the intake gasket, How about inspecting the vacuum hoses especailly at the map sensor. Here the thing you got. a vacuun leak. on a 5.7 a vacuum leak causes random misfire, by definition P0300 means 2 cylinders or more. By experience its a vacuum leak

P0303 mean Cylinder 3 Misfire.

Consider replacing the Cylinder 3 Spark Plug. If that does not settle it,replace the wires too.

Good luck.

Do an injector balance test and a cylinder leakage test. Lets make sure its not fuel related. Most important lets make sure you don't have a vacuum leak.

CODE 27 - Injector Control Circuit, output driver does not respond properly to the control signal

Code 27 MIL light options: OBDII
P0201 - Injector #1 Control Circuit
P0202 - Injector #2 Control Circuit
P0203 - Injector #3 Control Circuit
P0204 - Injector #4 Control Circuit
P0205 - Injector #5 Control Circuit
P0206 - Injector #6 Control Circuit

CODE 43 - Cylinder Misfire, or Ignition Primary Circuit

CODE $# MIL options: OBDII
P0300 - Multiple Cylinder Misfire
P0301 - Cylinder #1 Misfire
P0302 - Cylinder #2 Misfire
P0303 - Cylinder #3 Misfire
P0304 - Cylinder #4 Misfire
P0305 - Cylinder #5 Misfire
P0306 - Cylinder #6 Misfire
P0351 - Ignition Coil #1 Primary Circuit
P0352 - Ignition Coil #2 Primary Circuit
P0353 - Ignition Coil #3 Primary Circuit

faulty injector,missed...or inlet gasket leak,(spray crc wd 40)around inlet where it joins to clyinder head if it gets smoother running its leaking,vacuum leak,eg;hose off thats not seen or missed

sounds like spark plugs or spark plug cables are bad and it is in fact misfiring this happened to me in my car and my spark plug cables were bad