Jaguar Forums - Jaguar Enthusiasts Forum - Bad coil pack sounds just kind of like a rod knock

I thought for sure my engine was toast the other day. Gave my car to my wife to drive and she told me that it started running like shit and it was giving her a flashing check engine light.

when she got the car home I started it up and sure enough it was running like crap. Really running rough.

I open the hood and I was checking around to see if I had left the connector disconnected or a broken wire cause I had been missing around touching stuff earlier, but I couldn’t find any problem

but when I started it up again with the hood open this time I heard what sounded like a definite metal and metal sound. But it wasn’t consistent like you would have. If it was a rod it was more random and I couldn’t really narrow down where it was coming from. sound like it was coming from the top of the engine, so I thought maybe the supercharger was knocking rotors but I put my stethoscope on it and it didn’t sound bad at all. thought maybe it was a water pump but it didn’t really sound like it was coming from that location

Ended up hooking it up to my SDD looked at my mixture and I had some funky looking short term readings on bank two

I put up the oxygen sensor, voltages and current to look at those in bank 2 way out of whack. I was seeing numbers up around 25.

Put up the misfire counters and I was seeing the number six cylinder was just counting up like it was no tomorrow everything else was solid zero. Pull the number six coil pack and plug in the plug was wet. So I sprayed it down with some brakeclean and carb cleaner to get it dried off. Checked the gap it was fine.

Swapped coil packs from selling number six to cylinder number one and sure enough saw the misfire the coil to number one.

I had a spare car, so I had a whole set of coil packs. I took them into the house to try to put some numbers on them using my digital multimeter set on the diode mode. And I checked every combination with the leads, and One Direction, then reverse them, and did the same, and I put the readings on a piece of paper and looked at them.

somebody must’ve been in to the coil packs on the parts cart at one point because each coil I had a number representing its cylinder painted on the top of the coil except for two coil packs. One of the two coil packs had three white dots on it, and the other coil pack had a big white on it

Once I took all the readings of the spare coil packs, I checked the number six coil pack that was bad and it showed me which coils were good in which were bad

I grabbed the coil pack from the parts car that had the best readings and I installed it. I could tell as soon as I cranked it over that it was gonna be OK. the car fired up ran smooth as silk. The knock sound was no longer there. Thank God. the exhaust smelted better than ever. Took her for a couple of test drives and my check engine light went out and I hope it doesn’t come back on but so far it hasn’t.

ill Post a picture of the numbers that I got for measuring the coil packs and you can see that the numbers that are lower than the others are suspect coil packs. By the way, 06 STR had two different style coil packs in it I had six Denso, and two fomoco.

The parts car had all Denso

Hopefully this is helpful. Somebody has the same issue. It’s nice to be able to put a meter on it and be able to understand whether they’re not it means it’s good or bad.
https://cimg0.ibsrv.net/gimg/www.jag...9b9e688eb.jpeg
Not everybody has the ability to read the knock sensor, count, or mixture levels.