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Help! Cylinder Layout


Seasoned Member
Dec 17, 2011
Pueblo West, CO
My XLR/V(s)
2006 Light Platinum XLR
I’ve been off-site for some time, so if these questions are already answered, I couldn’t find them. To wit:

1) I’ve been getting intermittent "cylinder misfire" SES messages lately (on cylinders 1 & 5). Problem is, I can’t find the cylinder layout, so I don’t know for sure which ones they are. I found a crude layout for an STS, but I don’t know if they’re the same. Help!

2) I changed out the spark plugs, already, and cleaned up the dirt/debris in the plug "tubes" (vacuumed it w/ the plug out). What is the recommended torque for the spark plugs on the reinstall? I found one article that had it at 15 ft-lb, but that seems low to me.

3) I also cleaned up the ignition coils (delicately), but can’t find the recommended torque for the Torx-head screws. (Sure wish I had the service manuals…)

I also checked the ignition connector "tightness" on all the cylinders (a couple were a little loose, but w/ almost 73,000 miles I kind of expected that. Any suggestions and/or information will be sincerely appreciated. TIA

If you have the individual coil packs id swap them over to the other side and see if that changes anything. Check the intake manifold bolts. Look at the boots on the coil packs. Itdoes not take much for the spark to arc thru them. They would show a crack or burn on the rubber if bad

Ill have to double check but i believe 1357 on the passenger side 2468 on drivers
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Thanks, "Mickey". My problem is that I don’t know the cylinder layout; i.e., where is cylinder #1? If I find that out, I can zone in on cylinders 1&5 and see what gives. When I first changed out the spark plugs, 2 were noticeably looser than the others (which were pretty tight). When I put in the new plugs, I tightened them to what I had read was the correct torque (15 ft-lb, or 180 in-lb). It didn’t feel tight enough, tho, so I’m kinda thinking the "right" torque might be higher. 🤷‍♂️ If you have access to a Service Manual, I’d sure appreciate your telling me what it says for the spark plug torque and if there’s a torque value for the Torx bolt (screw?) that holds the coil pack in.

Your cylinder number recollection matches the one I have for the STS, but I really want to do this right, and be sure. Let me know if 1-3-5-7 are on the right-front side on the vehice, OK?

I’ll pull the coil packs on the front two cylinders, and compare them. If they look the same, I’ll swap them and see what happens. If one is "cooked" around its lower end, I’ll see if the problem follows the coil. If I can verify a weak (shorting) coil pack, I’ll hafta replace them on both of the failing cylinders (1 and 5). Right now, it’s running fine, but (as a computer Customer Engineer friend of mine told me a long time ago), "These things don’t heal."

Oh, BTW, I’ve had to tighten the intake manifold bolts twice now. Tough to get a wrench on them, tho, but an old, weird ignition wrench seems to do the best job. I acquired a set of crows-feet wrenches that help, but trying to get an accurate torque setting for them is trying, to be sure. As long as we’re talking torques, do you know the setting for the intake manifold bolts? I had seen 81 in-lb.
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Thanks for the cylinder info, "Fireduck". Any help w/ the spark plug torque values? I don’t have a clue if there are torque differences between the base and "V" engines. My intake manifold bolts were a little looser than ideal, so I re-tightened them, for the 3rd time now. I saw a value of 10 Newton-Meters referenced in another post (88.5 in-lb), so that’s what I used. If that’s wrong, I hope someone lets me know. 😎

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