Repair-It

Cylinder #5 misfire. What's weird is I had a premonition that it was a #5 misfire. Can't explain why. I think I will slap my new coil that I've had on the shelf in and see if that's all it is.

Check this out.

Pulled old coil. Looked like this: Those may be burn marks actually.

Threw my new coil on there that I bought from Rockauto back in December when it had the original misfire. Started it. Smooth again! Revved it up, brake torqued it a little. No issues. Not even going to test drive. Didn't even check the plug.

Pulled it out, goobered some dielectric grease on the tip, put it back in, done. 20 minutes. Super satisfying. 120k on SRX now.

Jamie drove the SRX tonight and said it was totally fine. Fixed.

4 months later and Jamie is reporting similar symptoms. No light yet. I just ordered another coil preemptively so I have it on hand.

I have yet to connect the Tech 2 to this vehicle which, unlike the STS, will have made it almost 3 years without having to need that. If I had a code, I could just use my cheap OBD-II scanner. But without a code, the Tech 2 has a lot of fancy misfire stuff that I could use to determine if there is a problem with an individual cylinder without actually requiring a code. Of course, if it is #5, then I won't be too happy as that coil is only 4 months old. Probably another one.

Just got back from a 20 minute drive or so. Everything I said seems to be correct, empirically. That's good.

I did various things like drive normally but also hammer on it. At the end I caught it misfiring when idling in drive in the garage. This screen is very handy. Also, throughout this whole thing, the check engine light never came on once. Why? Because the misfires that were detected were not exceeding the actual threshold for emissions compliance.

Here are all the pictures with time stamps to give an idea how it went. Also, it auto scales so that's cool, too.

It was pretty quickly revealed that #7 seems to be the culprit. Not sure if I need to care about #3. 7, 3 and 5 are all the passenger side bank, but I don't know if that means anything as the coils are individual, unless that head runs hotter and the coils fail sooner. I don't think I can conclude any of that with the data I have. 6:27pm 6:34pm. 6:35pm 6:35pm 6:35pm By the end it showed like 1 or 2 on #6 and #4 but I think that is meaningless. #7 clearly dominates which is why this graph is so incredibly useful.

I already ordered the coil so when I get it I may just put it in and redo this test. It may be that #3 will be next but it's not severe enough to be worried right now.

All hail the Tech 2!

Got home at like 3:50pm so Jamie could bring Ian to the doctor. Coil was delivered today. Swapped #7 (pass side rear-most) coil and was test driving by like 4:02pm.

Problem appears to be cured.

I will get an after shot with the Tech 2 when I get a chance. I snuck in this repair so Jamie could take her car to the appointment. She was going to take the STS but didn't need to because I swapped the coil in time (again).

I'm not saying I want the coils to fail, but this is so satisfying. It would have taken longer to swap the coil on my Caprice. One of those few things where a fancy engine makes service easier.

Do you get negative time for this repair?

kevm14 wrote:It may be that #3 will be next but it's not severe enough to be worried right now.

Turns out #3 comes right after #7 in the firing order. Chances are that #3 is fine. Still haven't retested with the Tech 2.

Looks like a grand total of 4 on #3. It only occurred when I let off at the top of like 2nd gear. I never saw it accumulate under WOT, even through the 1-2 shift. It may be that it is still the next one to go but I will wait for symptoms. As it is now it runs well and I felt zero misfires.

Jamie had to take Ian to the doctor (what is it with doctor's visits) again. She reported some shaking on the way there but not on the way back.

I ordered another coil.

If it was a huge pain in the ass to replace coils I'd have done them at the same time. But it's ridiculously easy so I'm doing it this way. Plus I want to see how tightly they actually fail relative to each other. I bet it's #3 but I'll have to scan some other time. Like the weekend.

If it is #3, that is 3 coils on the passenger side bank. Seems like quite a coincidence. But I have no theory other than perhaps that cylinder head runs hotter than the pass side for some reason. Or just random chance.