2013 GS 350 F sport 2, 3 5 cyl misfire
 

Hello everyone - I am out of ideas
cylinders 2, 3 and 5 are misfiring - replaced the following all known good components from another operating engine.
Swapped out plugs, coil packs, both set of injectors, the injector harnesses and the fuel injector module. Had the ECM sent out to a 3rd party company and they verified ECM is working as per design with no latched codes. Performed compression test on all cylinders avg is about 174psi with less than 10% difference between cylinders. Performed leak down test on 2,3 and 5, less than 5%. The misfire is NOT random and is present at all RPMs. I am thinking there is an issue with the harness, hopefully someone may have had the same issue. I do not have the schematic and about to purchase one online. Engine is not overheating and never did.
Any help would be appreciated - Thank you
2013 GS 350 F Sport RWD 6 cyl

What are the exact codes you are getting?

P0300
P0302
P0303
P0305
CEL is flashing
able to clear codes, start engine and same codes consistently and it does miss

Could be a timing issue.
Unfortunately, you need a very good professional to diagnose one of those.
Any peculiar history to this car?

Very unusual to have both banks throwing misfire codes, but only for one or two cylinders. The only time I ever had this type issue with my 3rd gen is when I bought (unknown to me) knock-off spark plugs. They only failed 2 years into installment.

I'd recommend two things before investing heavily on other things.
1) Swap the spark plug from cyl #1 with cyl #3. See if the misfire code goes to P0301 with no P0303. If it does, buy new Toyota/Lexus spark plugs from a dealer or known OEM supplier. If not...
2) Borescope cylinders #2, 3 and 5 and look for excessive carbon build up. If present, rectify.

Good luck.

The plugs have already been swapped out with known good ones - I have 2015 ES 350 that runs perfect and been swapping known good components from that engine, Cannot be timing as that would not affect only 3 cylinders and it is 2 different banks. I also performed a power balance test and verified that it is indeed a miss in that particular cylinder. The compression and leak down tests verified that the cylinder has proper compression and does not leak. Excessive carbon would may an adverse effect )slow down flame) but it would have to be a significant difference between cylinders - the engine prior had no issues. Carbon build up that excessive would indicate a previous concern, but,,,,,I will take a look and see.
I appreciate the input folks.

@jsharos442 - Besides first typically checking spark plugs and ignition coil packs and wires, check fuel injectors and check/clean the MAF.

If you have the OE spark plugs it's highly doubtful (percentage chance of winning the lottery) you have any bad spark plugs, especially more than one bad spark plug.

Swapping/moving known 'good cylinder' plugs around to different locations will help confirm whether the problem is plug or coil pack/wiring related. Just make sure you record on paper what you've moved 'from' & 'to' location-wise.

Used any fuel or fuel injector treatment recently? Run out of gas?

Been messing around (cleaning, etc.) in the engine bay prior to the misfire codes and CEL - where hose, harness/cable plug connections could have become unplugged or have water get in them?

I am not sure if you read my post - everything you mentioned has already been done, swapping components did NOT change the misfire to a different cylinder. To reiterate;
the components that have been swapped out are from a known well running engine, from a 2015 ES 350 which is my daily driver.
Did not use any fuel injection cleaner, did not run out of fuel and have not cleaned or messed in the engine compartment prior to this issue. will have to do so.
Does anyone have access to wiring schematic to this vehicle or know where I can get one? There are quite a few places I can purchase, not sure if anyone has a PDF on hand.
Thanks

Double check your spark plug part numbers.

Per LexusPartsNow.com.

2013 GS350 (2GR-FSE) uses 90919-12049 (same as the 3rd Gen GS)
2013 GS350 (2GR-FXE) uses 90919-01263 (F-Sport model I believe)
2015 ES350 (2GR-FE) uses 90919-01247

My experience is that the GS is really particular about spark plugs and I only use genuine OEM after multiple bad experiences with misfiring cylinders.

Original, factory installed spark plugs?

I suspect there are many, though maybe subtle, differences of various components for the GS 350 engine and the ES 350 engine.

Many of the external parts are the same - I did the research prior to swapping out the components. Plugs, coil packs, injectors and modules are all compatible. The GS engine has a few slight differences but is essentially the same engine. I even installed the GS "suspected" components in the ES and it runs fine, that validated to me that component was not the issue, and yes I even swapped the plugs.

Ok, if you've eliminated coils and spark plugs, then I suspect you have three electrical problems...specific to cylinder's 2, 3 and 5. Cylinders 3 and 5 use the same harness, cylinder 2 uses a different harness. I'd suspect those 3 electrical connectors to the coils. Make sure the contacts are clean (electrical contact cleaner), that all wires are firmly into the connector, and that the connector "snaps" into each coil. Maybe even wiggly the electrical connector/wire while it's running to see if there is a change at that cylinder.

If it's not electrical, or something previously recommended, then a good professional with diagnostic tools may be needed.

Good luck.

...one other thing, I believe the coils are grounded via the hold down screw (I may be confusing this with my Volvo), but I would clean the block area where it screws down to make sure each suspect cylinder coil is grounded properly. Just thinking out loud.

If I recall the ES and GS Cylinder heads are diffrent configs? I think. the the timming, Injector pulses and other are going to be diffrent including the ECU Map diffrences. What needs to be done is go back to the orginal all GS parts. Then detect the problems from there. It's kind of confusing to me as to what happen 1st, then what, and what, and what started wrong 1st with the GS correct spec parts? Likely his best bet is to put the GS stuff back, then take it to Lex/Toy and let them tell him what they dianose as the problem.

Starting at this point to research the ES350 vs GS350 confing is like working on a problem, then not seeing the forest for the trees. Even the cams and timing are diffrent to fire effecient combustion matches in the cylinders.

Let me clear things up if I can....
The GS started having 3 cylinders misfiring. I started swapping parts from my ES to the GS. After swapping parts the GS still had the exact same misfires in the same cylinders, in the meantime - I took the suspected parts from the GS and installed in the ES, the ES always has and still running fine with exchanged parts.
The heads may be different along with timing, ECU outputs etc. The fact remains that my ES is running flawlessly with all the coil packs, plugs, both set of injectors, the injector harness, and the injector module from the GS - I am fairly confident that none of the components are faulty, if any of them were my ES would have similar systems, IE no misfires or CEL.
I am thinking there may be an issue with the engine harness between the engine and the ECU, that's why I need the schematic.
Thank you

93SCMax - I think we are on the same page, after swapping all the components my conclusion is it must be an issue with the harness. I don't think it is with each coil as this happened all at once, what are the odds? My process is an anomaly in the harness between the engine and the ECU.
When I was doing some research I came across a schematic for a F engine. That schematic had a common connector in the harness with cylinders 2,3 and 5 - that is why I suspect the harness. In need of the correct schematic to verify my suspicion. Granted the F schematic is for a V8 but Lexus electrical systems are similar across the board.