Misfire at Idle
 

So right now my car is in a state of disarray. P0300 P0302 P219A P119E DTCs are all set and the car misfires at idle.

First some background story:

When I was installing my lightweight FW and clutch, I had noticed a slight oil leak underneath the motor. Knowing that the 13Y models had some issues with gaskets, I took the car to the dealership.

Around this time I developed the DTCs: P219A and P119E.
Something peculiar about the DTCs; after a DTC clear, the codes would only come back on after a period of idling. I drove 30 miles on the highway without any CEL coming on.
The dealership fixed my oil leak, it turned out to be from the lower cam cover plates.
Regarding the DTC, they told me that the problem was the A/F sensor (I had previously checked the voltages coming off the sensor and everything seemed OK but why argue with a dealership..). And since that part wasn't covered under warranty, I would have to buy it. So $220 later, I installed the new A/F sensor.

The CEL came back on again after a couple dozen miles. This time with 2 more codes. P0300 and P0302.

On a cold start, there is no popping, and there is no hissing. There aren't even any codes tripped until the RPMs fall <1000.
But when the RPMs are <1000, I can feel the vibrations from a slight misfire, and the RPMs fluctuate. When I read the 'Cylinder X Misfire' count values on the OFT, they start incrementing when the car is at idle with no throttle applied.
But when I apply some throttle, there are no more misfires, and the car feels fine, and drives fine.

Does anyone have any insight on this, or maybe a starting point on what to check next?
I have also already checked the intake for leaks, as well as cleaned the air filter and MAF sensor. MAF sensor voltage also looks OK.

Update: Yay dealer visit on wednesday!!

Update:

Car was in the shop for 3 weeks, with the techs constantly working on it. (Ran compression and leakdown test, vacuum tests, etc)
Tech diagnosed the problem to be the high pressure fuel pump, and it was replaced. Tech also ran a fuel system cleaner through the system.
CEL didn't come back on, and car was given back to me.

Today I when I was warming my car up, the CEL came back on. (Only happens under idle...)
Plugged in and read the code, and they were the same codes P219A, and P0302.

I'm watching the misfires occur on an OFT and cylinders 2 and 4 rack up some misfires, but heavily weighted toward cylinder 2.
Misfire counts would be 24+ on cylinder 2 and 1-2 on cylinder 4 before the counts would reset.
Also something I noticed... When starting an idle. The target fuel pressure in the rail would be about 4Mpa (580psi) .. but after 10-20 seconds of idling, the fuel pressure would rise to 10Mpa (1450psi).
However, when I apply throttle, the target fuel pressure and measured rail pressure are spot on equal. I'll upload a data file later today.
Could a clogged direct injector cause a rise in fuel rail pressure? Since 2 and 4 are on the same rail, could it be a clogged rail?

How's your AFR?

Back in the day, the first thing we would suspect would be a bad spark plug .......:iono:


humfrz

Right? Which is why I changed all the spark plugs and coil packs :iono:

I want to say .3-.4 leaner than the command AFR.
Under WOT it'll start borderline 13's and then creep down to mid 12's..

Datalogs:

IDLING http://datazap.me/u/raviolig/log-145...=1-3-7-9-10-11

WOT http://datazap.me/u/raviolig/log-145...g=2&data=1-3-9

Keep us posted...hope you get everything sorted out

Unless you were driving a Dodge/Plymouth...then the first question would be "is it raining?". Those things hated moisture...had an old Dodge with a slant 6 and a Plymouth with a 318, and if a dog pissed on a tree two blocks from the house, neither one would start! Ahhh, back in the day... good times.


Sorry OP, I felt compelled to share that with @humfrz...I hope you can figure out that miss. It would drive me nuts. Was it always those 2 cylinders? Have you tried swapping coils from one cylinder to another, then checking to see if the misfires move with the coils?

Ahh yes, I had a friend with one of those engines and he used to carry a spare T shirt around in the trunk to dry out the distributor ..... :D

OBTW, good idea about switching coil packs ...... but, the OP said he had changed the plugs and coil packs ...... :iono:


humfrz

Fuel injectors perhaps?

I was going to say coil packs but sounds like you already have that covered

Update: Put the stock flywheel back in. 200 miles in, and no light.

But.. I can still feel some roughness in the idle, OFT occasionally detects a misfire, and the car still runs slightly lean.

Obviously the root cause was not fixed.

Did you ever get this figured out? I’m having similar issues.