SRX cold start misfire

[Fast_Ed]

There must be a tipping point when you've replaced 5 of the 8 coils.. Funny how one side seems to have aged faster. More heat on that side for some reason?

The curse and blessing of the Saab di cassette is that your only option is to replace all four coils at once.

[kevm14]

Have I done 5? Or was it 4? I think it was the full passenger side bank. I have a spare on the shelf...

Took almost 2 years to work through all 4 on the passenger side bank.

Other head scratchers are that the SRX has the later design coils than my STS. I don't know how old they are (I guess I should look that up), but the STS has an engine cover while the SRX does not. One theory is under-hood heat can bake the coils. Well that didn't seem to save the SRX coils. They are not exactly going to run cool where they are located anyway, on top of the valve cover, under a rubber cover. Yes the engine cover would trap more heat but the rubber cover insulates better because it's fairly sealed (for splash/dirt protection mainly). The engine cover is more like putting a piece of plastic on top of the engine. It doesn't cover the sides or anything. And aside from aesthetics, it's for injector/engine noise insulation.

All that said, if I actually narrow down a driver's side coil as the next victim, I may very well replace it and then order 3 more and do them. Not sure yet. It is hardly any extra effort to do one at a time though. Very easy job. In fact the only overhead you'd save by doing all of them is getting the 1/4" drive socket and torx socket out, plus removing the rubber coil cover. That's it. Oh and opening the hood...They are all individually connected to their own harness and fastened separately.

[Fast_Ed]

All a matter of each person's car maintenance philosophy.

Not like I'm judging... I recently replaced only my #7 spark plug.

[kevm14]

Yeah it was pretty simple for me. Replacing onesy twosey allowed me to:
1) See how long they would all live
2) Use up all of the service life, at least until misfires occur
3) Generally prevent from having to buy a bunch of coils all at the same time

I think Bill may have brought up an interesting point about ones that are left that may not be performing as good as factory. It's hard to say. It could come down to arcing across the plug, or not, but perhaps fresh coils spark hotter and perhaps burn the fuel more completely.

[kevm14]

So I had to move the SRX to make room for the Roadmaster since I backed it in the garage to work on the rear axle brake lines.

After all day, I started it to move it back into the garage for the night. Not to be outdone, it started to misfire. Jamie has reported that it does still intermittently do this so I leapt out of the car to grab my Tech 2 and by the time I got back, the check engine light was actually flashing. Nice.

Then it stopped. But it threw a P0300. Uh oh. That's not what I wanted. I wanted a single cylinder misfire. Here is the misfire history:

20200301_201404_HDR.jpg

Hmm. I think I replaced all odd coils already and I think 5 and 7 are the rear two cylinders on the passenger side. I should probably inspect all coils to make sure there isn't oil leaking down there (it's a thing and would require doing the valve cover gaskets). I also remember seeing a GM TSB for coil grounds but it wasn't specific to the SRX. Maybe I'll look into that and see if there is a ground I should clean.

Also....I think it needs a thermostat. It seemed to take a long time to warm up. So I will order that, too (oops, forgot to add to my oil line order damnit). $41.21 shipped after tax and discount for an OEM thermostat and OEM gasket.

In other news, the SRX is pretty quick with no kids or stuff in it...I did a 2,000 rpm brake torque launch (misfire testing) and went to WOT off the brakes and I could swear I heard a tire chirp. That's sweet.

Definitely pays to drive the wife's car from time to time to find stuff. Not all the right stuff is going to get reported, and not in a timely manner, either...

[kevm14]

Interesting...

https://www.cadillacforums.com/threads/ ... s.1069760/

[kevm14]

https://www.cadillacforums.com/threads/ ... v8.976041/

I am going to inspect all the coils and see if anything looks amiss. Well...next weekend I guess.

It's funny. This has the second design coils and my STS has the first. I've had zero coil issues on my STS. And it still has the engine cover. The SRX didn't when I bought it which should help the coils run a little cooler. One of those things. In fact, when I list all the things I have done on the SRX (it isn't much), I've had like NONE of those issues on the STS. The ones that come immediately to mind are: wheel bearing, power steering lines, tie rod, and this coil issue. Oh yeah and the power steering pump back in like 2015.

[kevm14]

Alright so here's what I did:

I inspected every plug and coil on the passenger side bank. Everything looked 100%. No arcing, plugs looked perfect, etc. Car has around 137k. I did not inspect the (harness) plugs at the coils but they all felt clean and snapped together the same way. I also disconnected the passenger side coil harness plug (it feeds all the passenger bank coils) and did inspect the pins. They all looked good so I plugged it back in.

Here is the replacement history for my convenience:
- All 8 spark plugs in Jan 2017. 111,594 miles
- #5 coil in Sept 2017 at 120k
- #7 coil in Feb 2018 at 122k
- #3 coil in Feb 2018 at 122k
- #1 coil in July 2019 at around 133k

So recall that the hits I saw on the misfire history were #5 (worst) and #7. Well it turns out the #5 coil is the oldest new coil that I replaced (per above). But that also means it only has 17k on it. So rather than just throw more coils at it, I switched the coils around. Here is the map:
- I moved the coil from #1 to #5
- I moved the coil from #3 to #7
- I moved the coil from #5 to #1
- I moved the coil from #7 on #3

I did reset the P0300 and the misfire history reset with it. I will monitor. If I get misfire history on #1 and #3 (used to be #5 and #7, respectively), then I guess those coils are bad and I will replace them. If the misfires stay on #5 and #7, I may do all plugs again since that is cheap and easy. I'm not going to entertain further misfires on those cylinders until I get that far. It is likely ignition related.

[kevm14]

I still feel a mild shake at idle but only in park. Super smooth in drive. So I unplugged each coil, looked at the electrical connector (no discoloration on the pins or anything) and sprayed some contact cleaner in each one. Plugged it all back in, still doing the same thing. I don't think it is a harness/wiring issue.

Maybe I will scan it again tomorrow when I rotate and see if anything else is going on (like misfire history).

I do have a new one on the shelf so I could replace the ones that used to be in #5 or #7 and swap it to see if the symptoms go away but I don't know if the symptom is reliable enough. I'd rather have a misfire code on a specific cylinder or history that is a smoking gun.

[kevm14]

Not sure how much I trust this but here's what it did just now in the garage. I revved it a little, put it in reverse, back to park, back to reverse, brake torqued in reverse, back to park, revved it and that sort of routine.

20200315_125956_HDR.jpg

Still not the smoking gun I am looking for though.

#3 came from #7 which WAS one of the misfiring cylinders but #5 was way worse and that is moved to #1. Miniscule hits on #1.

Plus #7 has some hits and that came from #3 which was even newer than the other two.

I'm sort of torn on what to do next. I think I might do all 8 plugs again. I am considering all 8 coils. Or maybe just the pass bank. Or even less than that. Can't really decide.