UPDATE: I decided on having the injectors serviced. All 16 were sent to be cleaned and checked with the belief I had one or more of the direct injectors with an issue. All port injectors tested normal. Unfortunately, the direct injectors cannot be tested before they are cleaned. So they are serviced first, then tested for operation after cleaning. After reassembly, the car is fixed. All of the fuel was exchanged before the first start.

SIDE STORY: Dealing with this issue has spanned 7 weeks. 6 weeks after the F went down, our is350 began showing the same symptoms. Misfires, very lean, but is only missing when it was running on the port injectors. 4 days after the is350 began running rough, my truck began showing the same symptoms. Misfires, running lean, etc. The truck is simple enough to move the injectors, so I swapped them. The injector was identified as the culprit of the misfire. The is350 has not been 100% diagnosed yet but it goes to the dealer tomorrow since it still is under warranty. I suspect the injectors will be found as the issue on that vehicle as well. Within a 7 week span I have had injector failures confirmed on two of my vehicles and will likely be found to be the issue on all 3. All 3 vehicles get 91 fuel from the same station. I believe the fuel station has some sort of contamination. Currently getting a sample of the fuel tested for contaminants and all injectors out of my truck tested to see if they can identify what has gone wrong with them. This has been the most unusual thing I've ever seen.

Looking for some troubleshooting help. Over the last few days the car felt like it was starting to develop a misfire occasionally. On Thursday, it definitely had a misfire. It set codes for cylinder #2, and #3 misfire. After that I monitored fuel trims. Long terms were between +25 to +39 depending on throttle input. Car did not want to pull its self past 3K rpm, it fell on its face hard.

Start diagnosing Friday after work. Smoke tested the engine, absolutely zero vacuum leaks. Valley plate was done about 3k miles ago, all seals and vacuum hoses are new PCV ETC. I thought mass air data looked a little skewed so I put on a new Denso mass air, no change. Looking at misfires now, it is missing bad on #8, and #1, no longer on #2 and #3 for some reason. Misfires seem to slightly decrease if rpm is raised. Coils and plugs were moved. Misfires have stayed on #8, and #1. The car is setting codes P0301, P0308, and P0300. In the permanent codes it has P0102 - mass air flow circuit low. P0113 - intake air temperature circuit high. I have glanced over the wiring loom and did not see any damage to it, wiggled the connector and wires. Both upstream O2 sensors are new. One is brand new, the other is new(er). High pressure fuel data looks good. Actual matches desired. High side fuel pressure holds steady when the engine is off, so I don't believe it is a leaking direct injector. At this point, I don't believe the misfires are ignition related. Something seems to be throwing off the fueling and I am not sure what at this point. Exhaust smells very rich, almost raw sometimes.

Car has PPE long tubes, Joe Z intake elbow with factory air box, and RR tune. Car has had the mods since nearly new and has had tens of thousands of miles with them. Anyone with some ideas or experience with something similar would be super helpful.

 

Update on further diag as of this morning:

Tested low pressure fuel system. Pressure is within spec 50 psi key on engine off, 60 psi engine running. I have ohm tested all 8 direct injectors, all 8 ohm test the same and within spec. The misfires still seem to be related to the direct injection system. On cold start, it seems to run okay aside from it hunting for an idle for s few seconds but once it switches to the direct system at an idle, misfires start counting on cylinder 8 and 1 on the scanner. I can bring the rpms up slightly and the misfires definitely decrease but I am not sure they totally stop. Engine can be revved pretty well. I can run it up to 5K rpm in park and it seems fairly smooth but once it comes down around 1K rpm at idle the misfires start racking up. I am going to compression test just to get a good mechanical baseline. At this point, I am at a dead end of what to look at next. Again no codes other than the P0308, P0301 and P0300. I have disregarded the mass air related codes at this point. I believe they were set from me unplugging the mass air while the engine was running during my initial test. Another note, when the scanner is showing the car is running on the direct system and missing hard, I can kill #8 and #1 injector independently and get.a response from the motor so I don't have a reason to believe the two injectors are completely non-functioning but maybe not working 100% correctly. What I am hung up on is that the fuel trims exactly mirror each other bank to bank. Sometimes down the hundredth of a decimal they are the same. The peaks and valleys are identical when graphed. almost making me think the ECM is getting bad data from something but I have not been able to pick out any data that looks skewed on the scanner.

 

Sounds like water in the gas tank. Have you recently run an injector cleaner like BG44K? That might help too. The other thought is a Lexus sourced MAF. Sometimes aftermarket isn't the best option, especially with MAF and O2 sensors. I got my MAF from Amayama, and it was significantly cheaper than US based sources.

 

I thought maybe fuel contamination, I did recently put fuel in it but it did not start the symptoms immediately afterwards. I have not run 44K yet although I typically do at every oil change interval. The mass air is a Denso but did not come from Lexus. I put the original back on but symptoms are exactly the same as of now.

 

Did you just change your oil in the last 200 miles? Also +1 denso maf is a must, never clean it just direct replace. Do you have an AOS? Any vacuum leak even tiny, will cause absolute mayhem

 

No recent oil change. It has about 3K on the current oil. It did had an AOS at one point but I removed it about 2 month ago due to vacuum leaks. I have smoke tested it again Friday night. I am 100% confident there are no vacuum leaks, my machine lets me put a good amount of pressure on it and there was absolutely nothing.. The fuel trims, the last time I drove it tended to trim more toward zero, but never went below about +19. I saw them as high as +39 with the cruise set at 60. Again both banks fuel trims exactly mirror each other during this behavior.

 

What are your o2 sensors reading for air fuel mixture? Either in AFR or lambda. Fuel trims are nice to know but they could be anywhere, sure in a perfect world they would be at 0.0 but its hard to tell where they should be at with so many variables, its good to know they mirror each other on bank 1 and bank 2 which suggests its more of a global issue than just 1 bank itself. Also how many g/s are you seeing on the o2 sensors at idle? You should be around 3-6 g/s at temp around 800 rpm depending on your air density and elevation. Last one, have you uploaded the stock tune and ran that to see if it eliminated the issue?

 

B1S1 lambda is 1.1 at idle. B2S1 is between .9-1. Keep in mind the car will not idle down to where it normally does for some reason. Idle currently hangs around 1K, I assume due to the way it is running. That being said the g/s at 1000 rpm is about 8. at 2K rpm It is 14. This is about the same between either Denso mass air I have. The ecm behaves odd to me. Sometimes it picks up misfires on 1,3,7,8 and sometimes it shows no misfires even though it is running no differently. I have also run the car with both upstream O2 sensors disconnected and that made no difference either. I have moved plugs and coils every which way at this point and not gained any ground. I have not uploaded to stock tune. The car had the RR tune when I bought It and did not receive the handheld to flash it back. But, the car has been FBO and tuned for tens of thousand of miles so they're not new mods by any means. I have also taken a fuel sample and there does not appear to be any contamination.

 

Here is where I am at as of today:

I took the whole set of coil packs and spark plugs and swapped them bank to bank. Misfires have stayed on 1,3,7, and 8. So it seems I have something mainly wrong on bank 1. I hooked a vacuum gauge to the intake. Vacuum at the best idle I can get the car to do is right at 19 Hg of vacuum with a steady needle. This is at an idle of roughly 1,000 rpm as this is the lowest the car will now idle for some reason. I've put enough cold stats on the car, I am starting to finally see a trend. On a cold start, It starts up sort of sluggish. It goes into it's high idle briefly with no misses, Then what I would call the "air injection pump" comes on at a cold start misfires start (I know it does not have an air injection pump, but I am referring to whatever happens on these cars during a cold start that makes the much louder at a cold start until it shuts off. Possibly high ignition retard?). All during this time the scanner is showing the injection way of "port". Once the engine temp reaches 140, it switches the injection way to "direct" and missing start ticking up on 1,3,7, and 8. At that point it is a matter a seconds before the CEL start blinking and the engine begins to run even more poor once the CEL illuminates.

What I have also found is that I can clear the codes it sets, start the engine and immediately raise the rpm anywhere above about 1500, I can keep any misfire codes from setting. The higher I raise the rpm, the misfires start to decrease and the engine smooths out. Cylinder #3 is the last one to quit showing misfires. This happens around 3K rpm. Above 3K rpm virtually no misfires are counting across the engine. What is confusing about this is that the scanner is showing injection way of "direct" the whole time if I bring the rpm up gradually. Since my initial thoughts there was a fault on the direct system. If I snap the throttle the injection way changes to "either" briefly. I then compression tested #3 then on #2 where I am not picking up any misses, compression was within about 8-10 psi between the two cylinders. I have compression tested 3, of my 4 misfiring cylinders and all 3 are within 8-10 psi and matches #2 which I am using as my baseline for testing.

 

I'm not sure if the oil solenoids for the cam phasers are interchangeable bet. the banks, maybe try swapping them? and see if the misses move to the other bank. If not, I'd look at the cam phaser next, assuming no wiring issues. Probably a wild suggestion

 

I'll give it a shot, I have not moved those yet.

 

No luck on swapping the oil control solenoids. Also swapped cam sensors while I was there. I’m nearing the end of my abilities on this one. Tonight the car would not let me rev it much before setting the misfire codes as it was the day before. I have no idea what’s going on at this point. Misfires definitely pick up once coolant temp reaches 140 and the direct system comes online.

 

Not sure if you've mentioned above already, Have you tried reflashing to stock/factory tune? And maybe try swapping the two DI drivers, since you mentioned the misses are all on one side and seems to be DI related.

 

Unfortunately the stock tune is not an option, at least not an easy option anyway. I did not get the RR handheld when I purchased the car. I contacted the previous owner but he has been unable to find it. At first, I didn’t not believe it was an issue with the DI drivers since my misfiring cylinders did not share the same driver but I swapped them anyway, no change. At this point I believe it is something with one or more of the DI injectors or possibly a high pressure pump. The car can run on the port injectors 100% misfire free. Trying to get it narrowed down from there will be the tricky part.

 

I bet you could get someone on the forum to lend you their RR Handheld - especially with so many folks moving to the LOI tunes. Maybe you could find someone near Kansas.