Possible misfire?

KENNYSR31

MEMBER
2017 FORD FUSION
2.5L
4 CYL
2WD
AUTOMATIC
64,000 MILES

So, I bought this car about 2 months ago because it was a one owner with a lengthy maintenance record. I started noticing right off that while driving at a steady speed mostly (but even at other speeds but not as common) between 40-55 MPH there is a hiccup that jumps 2 or 300 RPMs for a second then drops back down. Also, I don't know if it's related, but I've noticed depending on how I'm accelerating there is a chugging sputter sometimes in that same are when shifting around the 40-50 MPH area. Overall, it seems as it drives fine and at higher speeds it happens much less often drives mostly smoothly at higher speeds. I changed out the spark plugs and that didn't make a difference. My buddy said possibly the coils but there's no engine light on so without replacing all four which I don't have the money to do unless for sure that'll correct the issue, I don't want to go that route but from what I'm told without the engine light if it is a misfire, I'm the coils it wouldn't show on a scan. Any suggestions are helpful. Thanks

Tuesday, April 26th, 2022 AT 7:45 AM

3 Replies

KASEKENNY

MECHANIC
18,907 POSTS

Do you still have the old plugs? Can you get a picture of them so that we can see if this was truly misfiring?

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Basically, we need to do a couple things. Even though we have no codes, we still need to monitor the o2 sensor data while this is happening to find out if this is rich or lean. That will tell us if we have a possible ignition or fuel supply issue.

I am attaching a chart below that will help with this.

Next, we need to monitor the fuel pressure and find out if this is bouncing at all when this is happening.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

I am going to assume that this will all check out. If that is the case, we could have a torque converter issue.

So, one way to confirm this is if your vehicle has a manual shift option where you can change the gears, lower the gear and see if this misfire goes away.

Also, you can press the overdrive button and that will unlock the converter.

If this causes the issue to stop then we may have a torque converter issue.

Let me know what you find. Thanks

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Tuesday, April 26th, 2022 AT 9:49 AM

KENNYSR31

MEMBER
2 POSTS

So, we don't have the old spark plugs we changed out a couple weeks after I got it. My buddy is much more knowledgeable about vehicles than I am, he says he can check the fuel pressure tomorrow and I guess we can go from there. Just obviously looking for the cheapest guaranteed method of finding the issue without having to spend all kinds of money to do so likewise all your help is very appreciated.

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Tuesday, April 26th, 2022 AT 7:39 PM

KASEKENNY

MECHANIC
18,907 POSTS

Okay. Sounds good. Fuel pressure would make sense if this is in fact a misfire. However, if this is a torque converter issue then we are going to need to monitor the converter with a scan tool.

There is no other way that I am aware of to check the operation of it other than to monitor the torque converter clutch slip.

One way to get more info is to press the overdrive button as I said above.

So, keep us updated with what you find with this, and we can go from there.

Thanks

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Wednesday, April 27th, 2022 AT 11:30 AM