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Re: SRX cold start misfire

Posted: Sun Mar 15, 2020 12:34 pm
by kevm14
Since I have 1 new coil in a box, I ordered 7. And 8 plugs even though they aren't that old.

Total: $379.79

There is a $2/plug rebate so that'll be $16 back. $363.79 after rebate...

I have a feeling this is wasteful but then if it doesn't fix it, I guess something else is going on...

And maybe if it does fix it, that could be an indictment on my methods...oh boy, bad news either way. In my defense, I am still juggling multiple variables so it's still not going to pinpoint exactly what the issue was.

Re: SRX cold start misfire

Posted: Sun Mar 15, 2020 6:39 pm
by kevm14
Already submitted my $16 rebate online. Cool.

Re: SRX cold start misfire

Posted: Mon Mar 16, 2020 7:03 am
by kevm14
So this is dumb. The firing order is NOT the order of cylinders in that misfire graphic. I have no idea why they are ordered that way.

The actual firing order is: 1-2-7-3-4-5-6-8.

I feel like depending on the exact nature of the misfire, misfires in one cylinder can show up occasionally on a cylinder after that one in the firing order (nowhere near enough to light the MIL though). I have no idea why the list wouldn't be in firing order (it should just be 1-8 then). But here are the hits reformatted for firing order from the last scan:

1: 1 hit (pass side)
2: 3 hits (driver side)
7: 6 hits (pass side)
3: 9 hits (pass side)
4: 0 hits (driver side)
5: 1 hit (pass side)
6: 1 hit (driver side)
8: 1 hit (driver side)

So it is possible that some "soft misfires" (my term but call it incomplete burn) on #7 could in fact be coming from #2. And the hits on #3 could be coming more strongly from #3 and that coil came from #7 which did have quite a few hits on the last P0300. Also #5 and #7 are NOT next to each other in the firing order, and those two were clearly misfiring before. This is less scientific than I'd like but maybe the point is I am more trusting of misfire reports from non-adjacent cylinders (in terms of firing order). When it is that clean, I believe the results. In fact, a light was set. Pretty concrete. The pic I just posted is not clean at all, by comparison (no light/codes).

Now I could just ignore it and say...if I don't get a light, I shouldn't chase problems. But that's probably not the right answer given the history here, and long term incomplete burns (and occasional non-light-setting misfires) are not good for the cats. Or fuel economy.

The good news is, I will do plugs and coils and that should hopefully baseline those items. The thing is, neither the plugs nor all 4 coils on the pass bank should have anything wrong with them. And if they do, then do I 100% trust new parts? That's why I am reading the misfires rather than just throw parts at it (or why I have been doing that until now).

Still, you could say that if I did not have a Tech 2, maybe I would have just done all coils as soon as one seemed to be failing. I am still not convinced that would have been a 100% solution because it still seems like I have more early failures so even if I did all 8 originally, I'd still be faced with buying more right now. In fact it would probably just be the opposite situation. I could have bought all 8 before, and when I had early failures on certain cylinders, I may have specifically targeted the replacement rather than buy 8 MORE. Net coil purchases: same.

If on the other hand, in the very unlikely scenario that all of the unreplaced driver side coils are causing ALL of the hits on the passenger side, then I admit defeat. I doubt that is the case though. And I will never know the answer because I will be doing all plugs and coils...

I guess the only thing I could really do is replace the driver side coils and plugs and run it for a week and see what happens. Probably not going to do that. The available evidence does not support that theory.

Re: SRX cold start misfire

Posted: Wed Mar 18, 2020 9:18 am
by kevm14
Coils and plugs came in...all I have to do is install them.

Re: SRX cold start misfire

Posted: Sat Mar 21, 2020 3:44 pm
by kevm14
Installed them. Everything looked good that I took out. No oil on anything. Plugs looked good and gap was good.

It seemed to be doing the same thing off a cold start but it maybe was a little smoother at least (minor, occasional shakes in park, nothing in drive). Drove it around and it was pretty damn smooth. I think whatever this is seems to happen right off a cold start so I will have to be more targeted in my diagnosis.

I still think I had a max of 2 failing coils and I don't think there was anything wrong with any of the plugs. So that was kind of a waste. However, this may have been a necessary step if something like this happens again. And worst case, if it needs more coils down the road, I have at least 6 that are probably good. I labeled all of them and even stuck the plugs in the ends.

Further theories would be something like a vacuum leak or leaking intake manifold gaskets. I can try retorquing the bolts (after it cools).

There was something blocking the rear of the intake manifold so I was not able to feel the PCV breather hose (the one that caused lean codes on my STS). And that's the thing. I drove around and fuel trims were fine, less than +10% on both banks. Now an individual cylinder vacuum leak like an intake gasket wouldn't show up as well on the whole bank so that's something but otherwise I'd expect other codes before I just get a couple random misfires. On the STS, I don't recall any misfires when I had the lean codes, in fact.

Jury is still out I guess. Needs more time/driving. Feel like I wasted money though...

Re: SRX cold start misfire

Posted: Tue Feb 16, 2021 8:19 am
by kevm14
Jamie started the SRX to bring Owen to school and texted me that the car was shaking and the check engine light was on.

I went outside and by then it had stopped. Scanned for codes and there were NO current codes but there was a pending P0305 (#5 misfire).
20210216_080746_HDR.jpg

There is one piece of info that makes this slightly interesting. On Sunday I moved the car to the driveway, and then back to the garage to make room to work on my tractor trans fluid job. So that was a cold start with 20 seconds, shut it off, then another cold start and shut off. Makes me wonder if a fuel injector is a little leaky. Should I throw a #5 fuel injector at it? Should I throw all 8 fuel injectors at it? It always starts up quickly so there isn't any evidence to suggest that an injector is actually leaking down the entire fuel rail or something. I also can't remember if Jamie went to the store after that or not...

I think it has somewhere in the neighborhood of 145k at this point. It's actually not that far from my STS (which has seemingly needed a lot more things).

I guess I'll continue to think about it. Maybe the Tech 2 can show individual cylinder trims? I thought it had the capability to do that....could also check regular trims though that won't narrow down to a cylinder.

For what it's worth, these injectors are shockingly cheap. They are on the order of 1/2 the price of the coils actually. Rockauto shows $30/ea for OEM AC Delcos, brand new. Plus a set of O-rings at $12. That's incredible. Does that change the math here?

Re: SRX cold start misfire

Posted: Fri Feb 19, 2021 9:43 am
by kevm14
I got my hands back on the Tech 2 and scanned it.

A couple of things to note and mostly nothing conclusive.

- It ran fine but did have a very occasional miss that I could feel. It was so occasional and mild that it didn't even register on the misfire graph on the Tech 2. I also think it's been doing this for a long time.
- I did see some knock detected and spark retard when I revved it. I don't know if this is normal but it seems a little odd to me. Jamie claims she's still using 93 but it's Cumberland not Shell even though I harp on that all the time.
- Long term trims were like 10% on bank 2 which is the even bank. Bank 1 was less like maybe 5% or even under. Overall no smoking gun there.
- I did not see any individual cylinder trim stuff. So that was a dead end.
- There is an injector shutoff test (I think it's called cylinder balance). You can shut off any of the 8 injectors individually while the engine idles and look at stuff. I did that. It felt like the same miss each time I did it, and the idle vacuum went from around 33 kPA to around 35-36 meaning each cylinder was pulling its own weight, evenly. Still a dead end.
- I did scan all modules for codes. It had a stored P0300 (multiple random misfire) but I don't know how old it was. I reset it. It also had some other codes that were unrelated, mostly that the power window auto up had not been learned and this must have been all the way back from when I did the battery. You'd think they would have gone away because I checked all the windows and they were all programmed. Kind of odd. But I reset everything anyway.
- There is another test and really this is the only lead I have. It does have an injector balance test. Unfortunately it's a manual process but it is way more convenient than having the injectors flow tested somewhere. Basically you connect a fuel pressure gauge, key on, and start the test by selecting a cylinder to test. It will pulse the injector some number of times in a controlled manner. You then record the fuel rail pressure drop. Reset and do again for all cylinders. This will tell you if any injector is an outlier (either way under or over flowing fuel). This would be a very good test to perform before I just throw some injectors at it.

So that's the plan. I will do that test and see what that does. It seems like it SHOULD have an injector issue based on what I know but I'm not sure it will be obvious from this test, especially if it's not misfiring at the time I do the test. Easy enough to try.

Bonus thought: Maybe the SRX needs an Italian tune-up. I rarely drive it anymore and making matters worse, as I said, she uses Cumberland which may not be Top Tier. Maybe I'm onto something here. Could try an Italian tune-up and maybe a Seafoam or similar treatment. And maybe guilt her into driving a little further to Shell, especially if that actually seems to have a positive result.

Re: SRX cold start misfire

Posted: Sun Feb 21, 2021 7:18 am
by kevm14
Did the injector balance test.

https://youtu.be/0lKhOs3my2A

The result is all of the injectors flow equally.

Re: SRX cold start misfire

Posted: Wed Feb 24, 2021 7:23 pm
by kevm14
Decided to go out and get some Shell 93. I was also going to add the Techron and Heet. And after getting gas and adding those things I was going to do some Italian tuneup on this thing. So I figured I should check the oil first. Good thing I did!!

It was 2 quarts low. Whoops. 6200 miles into this oil change and I've added nothing. My bad. It takes 8.5 quarts but 2 quarts low is still not good since I was planning on zinging it off the redline a bunch of times. Also the computer says 50% life remaining which is way too much.

Added the oil and drove to Shell, added the things, got gas and started driving around.

This car is geared tall. As a function of the extra weight over my STS and I think the taller gearing (due partly to the tire height but also transmission gear spacing) it does feel slower than my STS. It's the same engine so this shouldn't be too surprising.

When I say tall, I mean that I was not quite at redline in 3rd gear and I was going over 110 mph. Geez. It's a 6-speed!

Here are the cruising RPMs in 6th. Like I said, it's tall. Too tall really. 1800 rpm @ 70? What is this, a diesel?
20210224_190107.jpg
Anyway, I flogged this thing pretty thoroughly with lots of redline shifts, coasting down from redline and the whole bit, per decarboning technique (i.e. Italian tuneup). This also allowed me to check drivetrain function. With the exception of a wheel imbalance, it passed. Zero issues, no warning lights, no funny shifts, no engine misfires. It all worked perfectly at 144k. Even idles smoothly still. Needs Hawk HPS pads but that's another matter...

I guess I'll revisit this thread if the misfire occurs again. And it probably will.