Fuel Pressure on Kia GDi system

[Ginger FerroChrome]

Hello! I just need some advice. I am trying to diagnose a misfire on my '13 Optima 2.4L. Timing is good, tried swapping the coils to no avail. Now I am on to checking the fuel pressure. So, a couple of things. One chapter of the book says pressure from the low pressure line should be 338-348kPa at idle, another chapter says 495-520kPa. The gauge bounces quite a bit, which I assume is due to the action of the HPFP, but tops out at exactly 520, so I suppose that is good, right?

But, I also test fuel pressure drop after shutoff. Seems to loose about 8lbs in 5 min (sorry for using different scales here). Is that too much? And do you guys think that could be the source of my problem? It is just a P0302 (cyl 2 mis), She stumbles just a little and leaves a bit of soot out the back, but drives fine and no pinging, knocking, or backfiring.
This is my first time working on a GDi engine so I really appreciate the help.

 

[NibbanaBanana]

How about spark plugs? Did you pull the #2 plug and look at it? I just has a miss caused by a plug with a cracked insulator.

 

[Devo242]

Is the car up to date with all recalls? There is one in particular on certain 2013-14 Optimas for low pressure fuel hose leaking (NHTSA Campaign Number: 22V093000).

 

[Ginger FerroChrome]

How about spark plugs? Did you pull the #2 plug and look at it? I just has a miss caused by a plug with a cracked insulator.

They look okay. At 98k I might replace them anyway but I figured I already had the fuel gauge so I might as well check before throwing parts.

Is the car up to date with all recalls? There is one in particular on certain 2013-14 Optimas for low pressure fuel hose leaking (NHTSA Campaign Number: 22V093000).

Yes, that recall is done. I think the only overdue recall (so far) is the ABS spontaneously combusting.

 

[Mechanician]

Hello! I just need some advice. I am trying to diagnose a misfire on my '13 Optima 2.4L. Timing is good, tried swapping the coils to no avail. Now I am on to checking the fuel pressure. So, a couple of things. One chapter of the book says pressure from the low pressure line should be 338-348kPa at idle, another chapter says 495-520kPa. The gauge bounces quite a bit, which I assume is due to the action of the HPFP, but tops out at exactly 520, so I suppose that is good, right?

But, I also test fuel pressure drop after shutoff. Seems to loose about 8lbs in 5 min (sorry for using different scales here). Is that too much? And do you guys think that could be the source of my problem? It is just a P0302 (cyl 2 mis), She stumbles just a little and leaves a bit of soot out the back, but drives fine and no pinging, knocking, or backfiring.
This is my first time working on a GDi engine so I really appreciate the help.

Low fuel pressure is unlikely to affect only one cylinder.
Try swapping both the plug and coil, to another cylinder and see if the miss follows them.

 

[D60]

Yeah these are stupid easy to access. Move everything from #2 elsewhere and see if the misfire follows.

 

[Ginger FerroChrome]

Tried that. I'm just wondering if the fuel dropping off after shuttoff means a leaky injector. I didn't figure it was the likely culprit but worth an ask.

 

[Bladecutter]

I am trying to diagnose a misfire on my '13 Optima 2.4L.
Timing is good, tried swapping the coils to no avail.
Now I am on to checking the fuel pressure.

And do you guys think that could be the source of my problem?
It is just a P0302 (cyl 2 mis), She stumbles just a little and leaves a bit of soot out the back, but drives fine and no pinging, knocking, or backfiring.

How many miles on you 2013 Optima?
Stumble only off idle, or at all speeds, or only at highway speeds, at low throttle openings, high throttle openings, or at all times?

It is doubtful you have a fuel supply issue if the errors are only on 1 cylinder.
Besides, you are better off checking fuel pressure on a GDI engine with a scantool.

As mentioned before, if you haven't already, move the ignition coil to cylinder 1, and the spark plug to cylinder 3, and if the misfire follows one of those two items, then that is your culprit.
If the misfire stays in cylinder 2 however, then you will need to ohm test the fuel injector, and then compression and leak down test that cylinder bore.