2000 Chevy silverado LS 5.3L misfire of cylinder 2 that mechanics can not figure out. It’s intermittent, was at shop for a week and it would not throw a code nor run rough. Picked it up today and ran fine until we almost got home. Doing it again. The shop originally said it was O2 sensor and replaced. Dealing with this going on three weeks and out $400 bucks. Compression is good, tune up done a year ago, fuel pump replace a year ago as well as fuel filter. Anybody have any clue what it could be? Weird that it’s intermittent. Also shooed cleaned throttle body. They can get the history on the check engine light and it says misfire on cylinder 2, approx 13000 misfires

 

https://carkiller.com/scottykilmer/howto/misfire-4/

 

The first thing I would do is to swap the #2 spark plug with the #4 spark plug and see if the misfire moves to the #4 cylinder.

If no change, then move the spark plugs back to their original cylinders and then swap the #2 and #4 spark plug wires to see if the misfire moves to the #4 cylinder.

If no change, then move the spark plug wires back to their original cylinders and then swap the #2 and #4 ignition coils to see if the misfire moves to the #4 cylinder.

If no change, then move the spark plug wires back to their original cylinders and then swap the #2 and #4 fuel injectors to see if the misfire moves to the #4 cylinder.

If still no change, then you'll need to investigate the ignition wiring & fuel injection wiring to the #4 cylinder.

All this assumes that you have a decent OBDII code reader/live data scanner that will allow you to monitor cylinder misfires.

If you do not have an OBDII code reader/live data scanner that can do that, and you have an Android device, then I suggest you get the following Bluetooth OBDII dongle and the Torque Pro app. Total cost will be under $25.


This setup will allow you to monitor cylinder misfire counts and virtually every other engine.emission system sensor installed on your engine, plus, it will allow you to save the data in an Excel-like spreadsheet for analysis on a PC. NOTE you will need to set the Torque Pro app up, and that takes less than 30 minutes.

Good Luck!

 

The shop did all that when we took it back the third time. When we took it back the check engine light was on and they did live data. It was a Friday and they were about to close. They swapped all ignition components to see if it would do it and it didn’t the following Monday. They kept it all week and drove it everywhere and could not get it to do it while it was there. Picked it up Monday, drove it approximately 100 miles with no issues. Got about a mile home and light came back on and was running rough. At our wits end. Very reputable shop that we have used for years with no issues. They are very honest and trustworthy

 

the fault must be active for diagnostics to find the cause. When the fault is happening bring it back and have them view live misfire data for every cylinder. Bring it in and ask them to scan it now not later as the problem may disappear after it is shut off and cools down.

cylinder 2 may be the only cylinder setting a dtc but there may be misfires on more that cylinder 2. Watching live misfire data may give another clue for diagnosis.

 

Check for a worn pushrod tip and change the rocker with the worn pushrod. ....seriously!!

 

Assuming 100% confimable double checked, sacrificed to car gods that previous Diag is good, then the last things left are fuel injector/valve/pushrod/lifter/rocker arm.

A slightly bent valve has showed up once or twice for me, as a misfire.

How good a condition is the wire harness overall? The older the truck, the more Chevy's original cheap and thin insulation starts rubbing through or causing stress breaks.

Good luck, man!