Short term fuel trim should average around 0, while long term fuel trim ranging between -10 and +10 is considered normal. Based upon your results, both appear to be in the OK range.
Strange misfire (P0302) on my new Scion
- Thread starter Elkins45
- Start date
Sounds like you've narrowed it down to cylinder 2 and it's not the coil. Swap some plugs and eliminate the plugs as the root cause. Then it's on to the connector. Or maybe the fuel injector?
I bought a new plug and swapped it in for #2 with the original coil. It idled OK but missed under heavy throttle.
On the chance it actually is a compression issue caused by a stuck ring I’m going to give it a one cylinder Berryman’s soak. If that doesn’t fix it I’m going to seek professional help. If it’s the wiring or connector a real mechanic probably can track it down more efficiently than I can.
On the chance it actually is a compression issue caused by a stuck ring I’m going to give it a one cylinder Berryman’s soak. If that doesn’t fix it I’m going to seek professional help. If it’s the wiring or connector a real mechanic probably can track it down more efficiently than I can.
So if I am understanding - you did not put it in the scenario where your seeing the miss to get your trims?
Long term as mentioned +/-10% is acceptable and +/-5 is perfect. Short term fuel trims aren't wildly useful except in some special cases.
It would be good to track them under the miss scenario before you totally eliminate them. Its possible (probably not likely) that under heavy load when its missing the injectors are not pushing enough fuel - dirty or sticky or something. More specifically in this case, one specific injector. It won't show up as much, because its 1 out of 4 and your looking at the downstream average. If it holds steady at a higher LTFT - like 10++ while going up that hill - it certainly could still be an injector.
Replacing the coil connector with the pigtail is simple and cheap. If you can solder or use crimp connectors, it can be done in 30 minutes. These connectors are <$2.50 a piece (sold in a package of 4) from Amazon. If there is a break in the wire, it has to be near the connector, not further back in the wiring harness since simply disconnecting & reconnecting the different coils appears to exacerbate the symptoms.
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In my small town I don’t want to venture that far from home on a weekend in case I need a tow. The wait would be quite long because the local guy is fairly hit-or-miss outside 7 to 5 on weekdays. I’ll wait until Monday morning to try that.
I poured a bottle of Techron in the tank just in case it might help with a dirty injector.
Based on reading this thread, it's likely an injector or the computer itself decided to die. Sometimes injectors show clogging...i.e fuel where it should be dry, like the electrical connector areas. I would not remove the injectors right now, but I would try to disconnect the wiring harnesses and see precisely for the presence of liquid in the electrical plug area.
Could this be a slight intake manifold gasket leak like the one the effected the Toyota Matrix 1.8? This would cause lean induced misfires intermittently.
I understand that. You don’t get the same thing under hard acceleration? If not that’s sort of strange actually.
On my last test drive with a new plug in that cylinder I induced it by jamming the accelerator to the floor. It wasn’t as bad as during hill climbing, but you could definitely feel it and the CEL flashed but didn’t stay on.
I’m still completely perplexed as to why it’s always worse, and happens even at idle, with the new coil(s). There’s a part of me that wants to pull a coil off my 09 and swap it to see what it does, and to put the new coil in the 09 and see what it does, but I’m wary that it might break something that isn’t broken now.
Some of this sounds like what my sister has going on with her 06 Matrix, except it only gives a p0352 ignition coil circuit code. Especially the major shaking she's was talking about at higher speeds.Regulars here may know that I bought a 2012 Scion xB with 80k miles for $3000. The reason for the great price is that it has the defective super white paint and it has completely peeled off the roof and is now coming off the body panels in big sheets. This car was used as a security vehicle in a fancy golf resort HOA so it spent almost its entire life going 10-15 mph down residential streets. When I bought it the gauges showed an average MPG of 12.1 and an average speed of 7 mph LOL.
Anyway, it drove fine on the test drive but now 100 miles later it is having a big issue. It started with a little shuddering on acceleration but on the way home I was driving up a hill at 57mph with the cruise control set and it suddenly freaked out. The CEL and Trac off light started flashing, the engine speed dropped then revved hard, and the wheels/transmission started shuddering hard. I braked, kicked it into neutral and pulled over, but after just a few seconds it was gone and the lights went off. I pulled out again and as I approached 50 mph it started shuddering but not as hard. The code reader showed a P0302 (cylinder 2 misfire detected) code. I replaced all of the spark plugs and tried driving the same route again. The slight shuddering was gone but the same big problem happened again at the exact same place under load coming up the same hill, and this time the CEL light stayed on. Same code.
I bought a new Denso coil and replaced #2 today and it immediately made the issue much worse. There was a noticeable misfire at idle that wasn't there before. Putting the original coil back in resolved the idle issue. Thinking it might be a defective replacement I went to Autozone and bought another one, but it had the same issue and also threw the same code at idle, which it didn't even do before.
How does installing a new coil make the problem worse? What should I do next?
I'm really stating to be reminded of why I always preferred buying new cars LOL. My other Scion decided to do strange stuff last week as well. I'm now 1 for 3 with used Scions, and I sold the good one
This would make fuel trims very lean (in the positive) and the symptoms would be at idle and probably more so when cold.
Is the part number the same? If so I would want to try that.
It's possible that the problems is elsewhere (wiring or ECM) and the new coils are just not quite as good as the original... Not causing but aggravating the actual issue? It's just a theory.
We were looking at ECM as the most likely cause on my sister's car but it looks like it was already replaced in the past (there was a recall on 2005-2008 Corolla and matrix).
Sounds like a good time to just do a Berryman's piston soak on all cylinders. I add a few ounces and manually rotate with a socket and let it sit for a few hours and repeat a few times. IF any fluid remains, I'll suck it out with a brake bleeder and reinstall if they plugs look ok. Regardless, it's a good time to look over all the plugs to see their condition. Also, it's not a bad time to perhaps do a Seafoam top end carbon intake cleaning. Hopefully you get this figured out!
This can be checked by checking the spark plugs to see if they are running lean.
The Matrix I deal with had a gasket that reportedly failed according to the dealer....the misfires were not noticeable.
The fuel injector is the part not swapped around yet. He should try changing the injector locations to see if the code travels to a different cylinder.
The fuel pump could still be a culprit with a clogged up filter or something, but his long term fuel trim seems just about as solid as it can get and it's only happening on one cylinder. When I dealt with a dying fuel pump, the long term fuel trims were in the 41 percent range, and misfires would pop up on two of the older ignition coils(3 and 4).
A brief but probably meaningless update: I poured cylinder #2 full of Berryman’s yesterday and let it soak overnight. When I checked it this morning it was still full of fluid. Almost none had soaked through, so I think it’s not likely a problem with the oil control rings. Or maybe that’s bad because it should have soaked through? Or maybe that only tells me the top two rings still have a good seal?
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Mine leaked down over time, if you remember
OTOH, mine is significantly higher milage with much higher wear
How's the tailpipe and plug situation looking?
Does it look like it burns a lot of oil?
Have you had it long enough to do a consumption test?
I’ve only driven it 300 miles, but it looks like the level is down about 1/4” from when I changed it. Tailpipe doesn’t look bad. I’m going to keep driving it close to home with big doses of Berryman’s and Techron. I might do a “rolling” piston soak and do one cylinder at a time over the next few days. It sure was a lot easier to start after only doing #2 than on the old car when I did all four at once.
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Out of curiosity, it seems you're glossing over the coil connector, why? Cheap and easy to try, less effort than some of the other things you're doing or contemplating.
I would try that, personally.
I’ll probably get there eventually. I’m just leery of cutting into the factory wiring harness if I can avoid it.
