ap4u06

i have changed plugs, wires still getting number 5 misfire, could this be ignition coil going bad?

thanks,
ap4u06

ruley73

Yes, but it could also be a bad injector or low compression. You can rule out the ignition coil quickly by pulling the #5 boot off it and looking for spark arcing between the coil and the wire. The coil doesn't fail very often on these vehicles so a bad injector or bad compression on that cylinder seems more likely.

ap4u06

This was from last night on my scanner live data. Seems that it’s the coil that has gone bad.

ruley73

Nothing in these pictures indicates the coil is bad. The ignition system on this engine uses a waste spark design that fires 1/4, 2/5 and 3/6 at the same time. Knowing that and seeing 0 misfires on cylinder 2 actually suggests the coil is probably fine, but isn't a sure thing. Looking at live data only tells you how often each cylinder is misfiring. It doesn't tell you why. You need to do some real troubleshooting like I previously suggested to find the cause. Pull the # 5 wire off the coil while the engine is running. If you see & hear spark arcing between the coil tower and the plug wire end the coil is fine. Performing a compression check on cylinder 5 should be the next thing you do if that checks out fine. If compression is good, it's most likely a bad fuel injector.

ap4u06

So checked all wires to the coil. Has spark to all from the wires. How do I check compression on this vehicle?

Craig0320

Buy a compression tool first. My uncles 04 sieera 5.3 developed a dead miss on cylinder 4 a couple of months ago. Checked and had no compression. Turns out a piece of metal/aluminum trash got trapped between the valve and seat. End result it burnt a hole in the exhaust valve. Pull the head replaced it and motor runs perfect.