Misfire

Saw this, is this possible? Meaning firing order of 1, 3, 4, 2 and so it could be cylinder number 4 that is bad?

Hi,

Interesting one. I ran through the manuals and found nothing as far as firing order or cylinder identification. I would have thought, like you, this is crazy. LOL

So, after finding nothing, I went to the powertrain management schematics. Believe it or not, the ignition coils are at different locations based on if the vehicle has a smart key or not. Ugh!!! I can't believe it either.

I attached what I found in the schematic. In theory, cylinders 1-4 are as we know them to be. However, the coil can be located in different cylinders. (I don't even know if that makes sense to me) LOL

Take a look at the schematic and let me know your thoughts. Also, I went with a 2.4L 4 cylinder. There is a 2.0 turbo. If I got the wrong one, let me know.

Take care,

Joe

So, my misfire on 3 would be ignition coil 2 counting from left. With a smart immobilizer they mean a fob I am guessing.

I switched coils between 2nd and 3rd but it's still there. The fact that all were misfiring and that MAP p106 was there before I am sure means something. None pop up when check engine light come on now but maybe it takes a while for them to do.

Hi,

Yes, to your question about the FOB. If the misfire didn't move, it could be a few things such as lower compression in that cylinder, a faulty fuel injector, or an issue with the MAP.

The intake air temperature sensor is part of the MAP. If you have a live data scan tool, see if the reading from it seems possible. Also, let me know what the short-term fuel trims are.

One other thought. Disconnect the MAP and see what happens. It should go into a pre-programmed setting to allow it to run. It should also stop a misfire if the sensor is the cause.

Let me know what you find.

Joe

Disconnected the MAP and it was worse.

Okay, are you able to get the short-term fuel trims? Also, did you take notice of the IAT signal?

Let me know.

Joe

I will get fuel trims. What you mean by take notice? You mean get the value from scanner?

Hi,

Let's see what the trims are. As far as the IAT, you are exactly correct, the values. Let me know what you find.

Take care and enjoy the last little bit of Thanksgiving left. LOL

Joe

Here are some data. Also if the car is running and i pull each coil's harness the motor changes, all of them work, so this is weird.

Also, when the ignition is on, one of the wires is ground and the other shows nothing, i checked more than one harness and they were the same, once I start the car that ground becomes battery power on both harnesses i checked.

If you delete code and rev up the motor it feels good that's why i think it's just strange. Like no misfire at all once code is deleted and until it comes back on again.

How long does it take for the code to return? Also, I wasn't able to see results on the scanner, just the headings.

Let me know.

Joe

Sometimes fee miles before the check engine light is back. I just rewatched the video clip, you couldn't see the values?

Hi,

I attached a pic of what I'm seeing. Take a look.

Joe

Strange, i sent a full view video.

Took pictures and videos of all data, some may not apply.

More.

Hi,

I got it that time. LOL Interestingly, other than 300 misfires on the affected cylinder, I don't see anything that sends up a red flag.

By chance, have you checked engine compression? We may have a weak cylinder. If you look at the pic below, I feel the other things would cause more than a single cylinder to misfire. At this point, I would check compression. Here is a link that shows in general how it's done:

https://www.2carpros.com/articles/how-to-test-engine-compression

Starting with pic 2, I provided the diagnostics specific to a cylinder 3 misfire. One of the tests is compression. The manufacturer's specs are in the test. I know some of these things you have already done. Also, one test includes the use of an oscilloscope. I'm hoping your scanner can do it.

Let me know your thoughts or if I can help in any way.

Joe

See pics below.

Have not checked compression as if it was low i would think the misfire would be there all the time and not sometimes and wouldn't stop if i delete the code. But i will measure it.my scanner may have oscilloscope, i don't know if I will be able to measure it based on the description, I will try.

Hi,

The interesting thing about low compression in one cylinder is that it can cause a misfire at different times. It's just a theory at this point, but it is very possibly the cause.

Let me know what you find or if I can help in any way.

Take care,

Joe

150 PSI or so on all except cylinder 3 120 PSI.

Is it possible it's just stuck?

Hi,

That is enough difference to cause the problem. What to do is perform a wet test. Place about a tablespoon of motor oil in the affected cylinder and recheck it. If the compression jumps up near the others, then you have an issue with rings. If there is no change, it is likely related to one of the valves or even a head gasket.

Try the wet test and let me know the results. Also, based on the manual, they are all low. Take a look at the specs below. Also, more than 15psi difference is a problem.

Let me know what you find or if you have other questions.

Take care,

Joe

See pic below.

Ugh, my luck.

If we can get them all to 150, it should run good enough to eliminate the misfire and be drivable.

Let me know,

Joe

Yes, i know, because i think the misfire and compression are light at this point, not too bad. You think restore it product may help?

I really doubt it's valve, with valves it usually is continuous.

Hi,

Anything is possible. I've never used the product, but I have heard it has helped others. What I am surprised about is what they indicate minimum compression to be. I feel that is high.

Joe

Not following.

Hi,

First, the product you mentioned is what I'm referring to. I never used it. Also, what the manual indicates as minimum compression seems high to me. I thought it would have been lower.

Joe

Yes, same here. Doubt it should be this high, and if it was that the engine is running like it does now at such low readings, and doesn't make sense that three were all at 150. So, must be around that much. Plus, there is wear and tear. Maybe when it's new it was that high, but i doubt too. Thanks

You are very welcome. If you have a chance, let me know how things turn out for you. I'm interested in knowing.

Take good care of yourself.

Joe