I have a 17’ GSF, 59k miles. Owned for 7.5 years. Car has been reliable except for one leaking shock. Otherwise, car is amazing.

I recently got PPE UL headers installed and I can’t believe I didn’t do this mod sooner. Really wakes up the car. I have a RR racing valved catback and stock midpipe. After headers, I did have it tuned for E85. Car does sit for a few days and is not my daily driver.

2 weeks ago, I was WOT on freeway when car went into limp mode, rough idle. My local mechanic plugged into tech stream and codes came back as misfire on cylinder 2 bank 2. He suspected spark plugs as I haven’t changed them since I bought the car. Checked those, they were fine, however, still same code/rough idle issues.

He then checked the following, per his text to me:

“Put the stock file back on the car, no dice.



So far,



Spark Plugs tested good

Ign coils tested good

Swapped injector, good

Swapped Injector drivers, good.



Only thing left is the direct injector underneath the manifold.”



Apparently the direct injectors are hard to get to, so it’s a labor intensive job/expensive. The car has been good to me, so it’s strange that it’s doing this at such a low mileage. I am not the most mechanically-inclined, so forgive any incorrect terminology.

Any ideas/suggestions as to what could be the cause?

 

I'd run BG44K through it before doing anything. It's cheap and often solves injector pattern issues with just one tank of gas.

 

I have posted this TSB over at the IS500, LC500 and RC F forums because a few members over at the IS500 forum were having issues.

 

There are a couple of issues with the LSB. No IS F will be repaired under warranty, they're all too old. The DTC for this issue is specific and is not related to misfire codes. It's interesting to see Lexus has decided a new throttlebody and ventilation hoses are necessary to resolve this. For misfire codes, I would still start with injector cleaner, specifically BG44K, because I've seen it work well on any number of cars with a rough idle especially higher mileage cars or sporadically and infrequently driven ones.

 

Wouldn't hurt to do a compression test on that cylinder to rule that out.

 

Or a leakdown test. We have heard of burned valves on these engines.

 

Update:

Hello everyone and thank you for all the advice, much appreciated. Mechanic pulled out the cylinder 2 direct injector and found the injector seals to be bad on that specific injector.

I asked what could cause this, per the mechanic:

“There is speculation of bad fuel, causing corrosion. When we look into the hole where the injector meets the cylinder, there is a bit of rust there. Possibly a bit of water in the fuel.



Recommend to replace the injector. Special order part.”

They’ve replaced the following:

Replaced Port Injector

Replaced Spark Plug

Replaced Ignition Coil


I imagine a direct injector will be at least $500? It’s a special order part. Mechanic will order the part, install, and hopefully it is the solution to all of this.

 

Depends on where you buy and how long you're willing to wait. Amayama is pretty quick and usually very cost effective - not always, but always worth checking.

 

So I went to the Lexus dealer and purchased the correct injector for $600.

Question: could E85 ruin an injector?

 

Maybe. But the seals could definitely be affected by E85. That's usually where you have problems with alcohol fuels if the seals are not able to deal with it.

 

That’s what I read online about running E85 but car doesn’t get driven enough. It can draw in moisture and potentially jack up the fuel system. Best to run non e85 tune and use E30 blend when you want a bit more umph if car is not going to be driven often.

 

Update:

Installed new direct injector, but still have misfire on cylinder 2.

Per mechanic text:

“Still misfire cylinder 2.

But no open injector code. So we solved half the problem.



Pulled spark plug cyl 2, put another one in. Still misfire 2.



Switching injector boxes around now, yet again.”

Idk what to do now?

 

What about swap ignition coil pack?

 

I believe mechanic has done this, per his text to me:

“Replaced Port Injector

Replaced Spark Plug

Replaced Ignition Coil



There's nothing else”

 

Yes, there is something else. There's a driver for the coil in the ECM. It is time to replace the ECM for sure and see if that resolves the issue. It is also possible there is a bad (intermittent connection) pin in the connector to the ECM.




I have seen myself a failed ECM in a GS F, so it's not beyond the realm of possible at all. In this case, it was the power to the heater circuit on one of the O2 sensors, and I isolated it to the ECM by validating the wiring integrity and validating the sensor was good.