pottertj20

2014 IS250 is throwing random misfire codes. I have changed all plugs and coils. MAF will be changed today. Is there anything else that will cause this on these motors?.

Sasnuke

Welcome to the forum!

Maybe a little background on your 250 might be helpful.
What's the mileage?
How long has this been happening?
How was the condition of the plugs?
What fuel do you use?
What interval do you change engine oil at?

For the 2IS 250 this was a common issue due to carbon buildup.
This issue was resolved during the 2011 production year for 2IS 250 vehicles.
As yours is a 2014, it should not be plagued by this issue the 2IS had, which was excessive carbon buildup on the back of the intake valves.

pottertj20

It is a 2014 is250 F sport. It has 100200 miles on it. I am getting misfires on cyl1 & 2. I have changed plugs and coils and still get the code. The light only comes on after driving on way home from work approx 40 miles each way. It has been doing this for about two weeks now. I always use premium gas. I also checked for vacuum leaks and none was found. The old plugs looked kind of on the lean burning side. Tan in color.

Sasnuke

You have some decent mileage on the vehicle...my 2014 IS250 is about half that.
Since it's bank 1 and 2, then it's effecting both banks of the engine, which suggests a global issue possibly...like fuel.
If you're confident the fuel is good, then next step would be a compression test.
If you have a compression gauge, the results would be helpful.
If you don't have a gauge, they are fairly inexpensive...it doesn't have to be the best gauge out there.

Because of the high mileage, you may still have a natural buildup of carbon on the intake valves...the best thing would be to remove the plastic intake manifold and Seafoam the back of the valves.
After the Seafoam procedure, an oil change would be best.

If the MAF was the issue you would be getting other codes too.
The plugs were a good idea to change.
If you changed all the coils, chances are the old ones were fine. In the future try simply swapping the coils to other cylinders.
If the code follows the coil, then the coil is the issue, but if the code stays on the same cylinder, then the coil was fine.

pottertj20

I will do compression test this weekend. I will need to rip the upper intake off again. I bought the car in Aug with high miles. The car does not shake or exhibit erratic idle. What shocks me is the light only comes on on highway. I drove it last weekend on back roads and no light.

s3v3n

iTrader: (3)

Might be too late since you replaced the plugs and coils, but if you still have the old set, put them back. Then do a seafoam treatment via intake manifold vacuum.

Then just put the new set of plugs/coils afterwards.

I'm on the extreme side but if this happens to me, I would also cover the oil side and the gas tank side (seafoaming).

pottertj20

I did the CRC valve cleaner treatment before I did the plugs. I may put the old plugs in and do seafoam this weekend.

s3v3n

iTrader: (3)

Also worth checking if you haven't - PCV valve (if you haven't done this - worth replacing). It's less than 10 bucks.

idleninjaz

This is correct, but unfortunately I've still seen post-countermeasure 250s with carbon misfire.

Sasnuke

The reality is with Direct Injection carbon buildup is always going to be an issue.
On the 2IS there were other mitigating factors that made the problem even worse, but with the 250 there is going to be an expectation of carbon buildup after so many miles driven...which I think is where you are.
For 2IS usually the light came on when travelling on the highway, much like what you describe. In some cases the light would flash, indicating fail-safe mode, or limp mode (whatever you want to call it).

Since you're familiar with removing the intake manifold, I would do the Seafoam directly on the valves and intake runners. The vacuum port version is fine for those not comfortable with removing the manifold.
Too bad when you had it off the first time you didn't get right in there to see what the valves looked like...you might have noticed the buildup and done the Seafoam at the same time.
Since you didn't mention any driveability issues, I would assume the issue is minor and only at the beginning stages.

Sid03SVT

Also worth moving injectors around to check if the misfire code moves with the injectors, although it's a fairly involved process so if I were doing it I'd probably just be replacing them myself.

Sasnuke

That is a good idea, and I would be behind that except for the fact the pressure in the fuel rail of the direct injection system.
Without having the necessary tools to discharge the pressure properly, that could be a little on the dangerous side.

Sid03SVT

Not all that dangerous if you've worked with DI or dual injection before:
Pull the fuel pump fuse/relay
start car and run engine for 20 seconds, it will run rough as the pressure drops.
turn off engine
open fuel cap to release vapor pressure, reseat gas cap
disconnect battery
get everything out of the way to access fuel lines under hood
Slowly crack fuel line banjo bolt with shop towels around it as there will likely be a tiny bit of pressure in the system
A scan tool can provide a readout of pressure in the system, I don't own one so this method has worked for me on other DI/dual injection setups.
A Lexus shop manual will spell out a Lexus specific procedure, but I bet it's basically what I've typed here.
Obviously PPE should be worn (gloves & eye protection)
OP shouldn't attempt if they aren't comfortable working with a dual injection system.

Sasnuke

For something like this I wouldn't guess at the procedure...I would find the actual procedure.
There too many chances for something to go wrong.
It's a moot point at the end of the day, since it's not an injector anyways. The chances of injector 1 and 2 going at the same time is extremely likely to the point of impossible.

pottertj20

Thanks for the input guy's! I will be changing out the PCV this weekend. I changed the MAF last night and no code this morning. I will let you know how my drama is going. This is my first Lexus. I have a Tundra with 220K on it and is a beast and still runs like new. I pull a toy hauler camper and a boat all the time. I switched from BMW to Lexus after many years ow owning since the 80's. They all have their quirks.