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I drive a 2013 Suzuki swift w/ cvt. There is a hill I travel daily and sometimes if I drive too fast, the car suddenly shudders followed by a check engine light. I have a small ob2 scanner and the fault code was a P0301 cylinder 1 misfire. My problem is the car only does this on this one particular hill. On straight roads and others hills, it's fine. Has anyone experience this?
 

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You need to use a live data scanner and record the fuel trims LT/ST (in graph format) during the event, we would be rolling the dice by offering advice with no evidence..
 

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Surely the fuel trim(s) will be common to all four cylinders, how would that help with a fault code specific to a single cylinder?
 

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The fuel trims will tell if the missfire is a result of a lean run at full load..
If in fact the FT does not run full rich on full load, then we are justified to run a fuel test, flow and pressure..

Or maybe you have a better solution...
 

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If the fuel supply is verified good,(by trims) I would utilize a scope and qualify the coils and injectors electrically..

Or, maybe you have a better solution..
 

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Educate me - WHY would a lean run misfire be specific to cylinder #1 - WHY NOT a random misfire code (P0300)?
 

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Random would be triggered if the ECU could not specify a specific cylinder pulse

If the single cylinder is fuel starved, or the coil is failing under load, the ECU would trigger the specific cylinder

Keep in mind that the plug could also misfire if the gap is too large (high resistance/KV),
 

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I am aware you are cognizant of wave forms, put a scope on an engine with a lean run and you will see the difference in the spark lines between a lean/rich flame front...
 

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Random would be triggered if the ECU could not specify a specific cylinder pulse
Random is ALSO triggered when the misfire occurs on multiple cylinders, which is why I expect it to be triggered on a lean run - a P0301 indicates the misfire is on a single cylinder ONLY - which is why I would expect a P0301 to be an issue affecting a single cylinder rather than one that would most likely affect multiple cylinders.

I am aware you are cognizant of wave forms, put a scope on an engine with a lean run and you will see the difference in the spark lines between a lean/rich flame front...
Please assume that I am John Q. Public and do not have access to a scope or know how to read the waveforms.

If the single cylinder is fuel starved, or the coil is failing under load, the ECU would trigger the specific cylinder
Keep in mind that the plug could also misfire if the gap is too large (high resistance/KV),
If a single cylinder was fuel starved would this show clearly in the fuel trims?
Would a coil failing under load show clearly in the fuel trims?
if the plug gap were too large would this show clearly in the fuel trims?

Educate me.
 

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If a single cylinder was fuel starved would this show clearly in the fuel trims?
Simple answer, YES! Under full load..

Would a coil failing under load show clearly in the fuel trims?
I never suggested that would happen, that is why I suggested a wave form scan

if the plug gap were too large would this show clearly in the fuel trims?
Never said that, I referenced the type of high resistance (creating a misfire) on the waveform associated with a wide gap..
 

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Please assume that I am John Q. Public and do not have access to a scope or know how to read the wave forms.

Educate me.
If you were John Q, without the specialized equipment, you could resort to seeking educated help, or use the parts cannon...
Since I do not support the use of the cannon, I was looking for some direction with the recording of the Fuel trims..
It would be fruitless to start switching coils or plugs (low tech) as the issue only presents at high loads..
 

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Simple. FIRST determine the amount of miles (and condition) of the spark plugs to see if simple replacement is in order. Then if necessary, swap #1 coil with any other cylinder, rescan, and determine if the misfire follows to the new location to rule out a single coil malfunction / replacement need.;)

If still an issue we can go from there.
 
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Simple. FIRST determine the amount of miles (and condition) of the spark plugs to see if simple replacement is in order. Then if necessary, swap #1 coil with any other cylinder, rescan, and determine if the misfire follows to the new location to rule out a single coil malfunction / replacement need.;)

If still an issue we can go from there.
Great plan... off to the hill to duplicate the conditions...
 

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If a single cylinder was fuel starved would this show clearly in the fuel trims?
Simple answer, YES! Under full load..
Would it be cylinder specific?

Would a coil failing under load show clearly in the fuel trims?
I never suggested that would happen, that is why I suggested a wave form scan
if the plug gap were too large would this show clearly in the fuel trims?
Never said that, I referenced the type of high resistance (creating a misfire) on the waveform associated with a wide gap..
I'm not putting words in your mouth, just inquiring as to how knowledge of the fuel trims would help pin point the source of the misfire - so far you have failed to convince me that it would help in anyway.

Correct me if I'm wrong - the fuel trims are going to be an average of all four cylinders and even if I unplugged an injector, which would show up in the trims, and set a P030x code, knowledge of the fuel trims will not indicate which cylinder is affected.

It would be fruitless to start switching coils or plugs (low tech) as the issue only presents at high loads..
As Max has already suggested, switching coils is a simple & effective step requiring very little in terms of expertise & equipment to accomplish - it may be a high load symptom but the user has already indicated that he can reliably recreate the conditions under which it occurs.

Now I ask you, since I have proposed a course of action and you obviously disagree,
Educate me - show me how your proposed course of action will be any more effective than Max's simple coil swap - if I am correct in my understanding that the fuel trims will not pin point the misfiring cylinder, then the low tech method would actually be a more productive use of time & resources.
 
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No, the fuel trims would confirm or deny any fuel delivery issue.. we already know which cylinder, once we have confirmed the issue is other than fuel, then prove the bad component..

the parts flipping method would entail, running up/down the hill as each change is made.. but each to his own..
 

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Thank you - now - a few more questions ...

First - if I understand how the trims work correctly - a lean run misfire is going to be revealed by an excess of "unburned" oxygen, so the trim will go positive - is that correct?

Next - a misfire, for any reason other than fuel starvation, will also result in "unburned" oxygen, so again, the trim will go positive - there will also be unburned fuel in the exhaust, but as I understand it, the system is looking at the unburned oxygen level, and has no way to determine the unburned fuel level, this would require a more complex gas analyzer.

Last - am I correct in assuming that the fuel trim reveals an average of the "unburned" oxygen across all the engine cylinders?

Given that we cannot measure the unburned fuel, what exactly will we see in the fuel trim that says the cause is fuel starvation?
Given that only one cylinder has the issue, how much of a variation in the fuel trim are we likely to see, given the "masking" effect of the remaining three cylinders?
 

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I am looking for a relative change in fuel trim before the event and during, regardless of the miss, the FT should rise and stay topped at full load, if the FT degrades during the Full load, that would be my concern...

And so we are clear, as I tend to work with evidence I would not fiddle with any component until I have isolated the cause, changing components may induce additional symptoms or mask the original.. If you perform repairs on your own vehicle is does not matter if you make unnecessary changes, but a professional diagnostician would be married to a faulty vehicle until the issue is verified fixed.. This may cause unwanted come backs and customer dissatisfaction... also since I personally have a policy the there is no charge for a no fix, it is not in my interest to fudge and use the parts cannon.. That is why I perform the additional tests before touching any components...even pin fitment may disturb the system...
 

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The reason for asking the question is to get a clearer understanding of how the fuel trim works and to understand what it is you expect to see that will confirm the issue to be fuel related, or not, as the case might be.

It seems every answer you give me clouds the situation a little more,

I am looking for a relative change in fuel trim before the event and during, regardless of the miss, the FT should rise and stay topped at full load, if the FT degrades during the Full load, that would be my concern...
IF regardless of the miss, the FT should rise and stay topped at full load - what is it you hope to see - what would be the point of looking at the fuel trims? What do you mean by "degrades"?

And one more - doesn't the ECU "drop out" of closed loop mode on full load operation? Are the fuel trims even in play at this point?

What am I missing?
 

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What do you mean by "degrades"?

What am I missing?
Downward slope.. must use graph form..

I appreciate that you wish to learn, but I spent many hrs and $$$ to gain the knowledge and equipment, it is not possible to impart that in a couple of posts.. Practice and time will be your friend in understanding and recognizing the supplties..
 
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