V8Life

So I recently changed the spark plugs/plug seals on my LS since it was time and because the car had developed an extremely mild misfire. It was hard to tell it was there and never threw a check engine light but it would show up as a cylinder 4 misfire as a pending code on my scanner. After changing the spark plugs (used OEM) the misfire became more pronounced and would only occur between 2k and 3k rpms. At all other rpms the car ran fine. So i ended up changing the ignition coil for cylinder 4 with a denso ignition coil and after driving around the block i started getting a check engine light saying multiple cylinder misfire and my car started running like crap. After i shut the car off and turn it back it starts running normally for a bit before the misfire reappears. Any idea what is going on? I am at a loss.

Anfanger

Do you have any oil consumption?

V8Life

Yes but nothing that i would call excessive. Maybe a quart or so every few thousand miles.

Cape600L

check your wiring/connectors on the coil. The wiring gets brittle and the connectors can get the same. I had an issue like yours and ended up finding the wiring bad, not the coil. Lot's of kits on Eb#$ for replacing the connectors

V8Life

Thanks! I was planning on spraying the connectors with electric contact spray and taking a good look at the wiring/connectors in a couple of days. Will keep you posted.

ausLX

Am I reading that right? You changed all your spark plugs, but replaced them with used ones, not new ones?
Also, I'm going to go out on a limb and take a guess that your other ignition coils are different brands to the Denso coil you just put in, this is something that can cause misfires in multiple cylinders. Did you inspect all the other coils to make sure they are all the same.

V8Life

No, what i meant was that i replaced my sparkplugs with new OEM spark plugs. (Denso long lasting iridium). Also all my ignition coils are original OEM. This is the first time any of those components have been touched on my car.

Anfanger

What error codes do you get?

V8Life

I don't have a check engine light, but i had a pending code 304 which is a cylinder 4 misfire. After i let the car run for awhile and the misfire becomes more evident i have pending codes 300, 302, 304, 306. All this leads me to believe i have a ignition connector wiring issue. I will inspect them when i get a chance.

Anfanger

All those cylinders belong to the same bank. I wounder if there is an issue with corresponding MAF sensor or an air leak.

7milesout

Hoping to hear a follow up.

Anfanger - I think your thought process is going down the right track. It seems like it's not really a coil by coil issue. But, heck, I guess it could be. It doesn't seem so because I wouldn't think coils would fail all on one side at virtually the same time.