Hi everyone,

First off, I have a 2015 IS350 (yes I know I posted in the ISF forum) I’m doing this because supercharged ISF’s are far more common than 3IS and I’m hoping this can get more exposure. I’m having an issue where at WOT, the car will either completely cut out (RPM stops going up too) with no throttle response and go really lean (usually 18-22 AFR) before 3.5K RPM, or if I ease past 3.5K and floor it the car will jerk violently until I let off the gas. Both issues stop as soon as I get off the gas. I also recently noticed that from a dead stop if I give the car too much gas there will a jerk, like a misfire and the car will go lean. So it’s not just at WOT that the car is running weird. The jerk isn’t as violent as when I got WOT, however.

I got the supercharger installed two months ago and the car was fine initially after the install. I decided a week after to run ethanol to an E30 blend and the car was still running fine. At this point, I didn’t have an ethanol gauge yet (it was on the way) so I might’ve been a little over, and one night the car completely went into limp mode when I floored it. I had a code for the car running too lean and cleared it as well as filled up a little on pump gas. Afterwards, the car was able to pull again, but I noticed sometimes that at WOT in the upper RPM’s, the car would hesitate briefly before pulling hard again. After another week, the night this issue started happening, I had just added more ethanol to exactly E30 because I got the ethanol gauge installed. It was at E23 before I added more and it pulled amazing up until I added the extra 7%. I’m certain the extra ethanol did something but I don’t know what.

Initially, I thought it was the tune so I got multiple tunes from Rafi and none of them fixed the problem. I even went back to pump gas and the base supercharger tune, which worked before and STILL had the same problems. This leads me to believe it can’t possibly be the tune.

I had new spark plugs installed when I got everything done and I changed them out again today because I thought that was the issue. The old ones I took out today were gapped way too small (.022). The new ones were gapped by Rafi at (.025) but the problem is still there. I also verified the compression on my engine and it’s above specs (210 in five cylinders and 200 in one cylinder). I have no CEL. I asked Rafi about potential fueling issues and according to him, the stock fuel pump and injectors should be more than enough to run ethanol. Strangely, the car will have no problems going to redline with some boost at quarter ish throttle

I have attached some logs that are short because they are only of WOT pulls (about 6-8 each log). The first pull in the log will be the violent jerking. The few pulls afterwards will be the cutting out followed by the throttle closing after the cut out.

I just don’t understand why the car was completely fine before and now I can’t do more than half throttle. Even Rafi is perplexed by all of this. The only thing I haven’t done yet is check my fuel pump, filter, and injectors. Did the ethanol mess up one of those components since the problem is still present even with pump gas? I did notice the chargepipe was extremely loose when doing my plugs so maybe there’s an install error somewhere, or a vacuum/boost leak? But if so, why would the problem show up weeks later? I’m not sure at this point.. I really hope someone can help out or point me in the right direction.

Thank you.

 

I’m not extremely helpful with diagnosing issues, but the first thing on a boosted engine is always check for boost leaks. Check everywhere. Ethanol sort of acts like a cleaner. How many miles are on your car? Maybe the ethanol cleaned up some gunk and your fuel filter is clogged. I’d change that out and maybe run some quality fuel system cleaner through, if such a thing actually exists.

 

sounds like fuel cut, possibly boost leaks?

Id check for leaks, if youre saying the charge pipe felt loose than its possible the rest of the piping isnt secured. Could've wiggled out during your pulls (possibly why it was delayed in having issues).

 

Do you know of anyway to test the the fuel pump/filter without taking it apart? I only have 62K miles on my car so I find it hard that my filter is already defective, but it is definitely a possibility since you mentioned it cleans gunk out.

 

Sounds like the ethanol loosened some gunk and dumped it into the system. Clogged filter gummed up injector? Our old rx7 acted like this with a clogged cat. It’s a process of elimination but I bet the problem is not as significant as it seems. Diagnosing it will be the tough part. The fix is likely easy. Stay at it you’ll find it.

 

lol rr racing talking **** about indians on fb and sending emails about trump instead of selling a decent product

 

RR racing is the problem. I’d take all that off and get a refund. Enjoy Lexus reliability, not RR’s ****ty products.

 

A boost leak can cause a surge, but I think it would also cause a rich condition, correct? The lean condition insinuates it’s a fueling problem.

 

Bruh... Bahahaha

 

r r trash lol

 

I've had RR Racing mods on my car for years and zero issues as well as my friend who has their SC kit and had zero issues with his kit. But by all means go ahead and get a supercharger from another vendor and let us know how everything goes with the reliability of their kit? Curious minds would like to know🤔

 

You seem to have the same symptom as this guy RC350 with RR racing tune. Check out his video for the fix.

 

A boost leak will be lean under vac as it's sucking air into the system through the leak, but under boost it will run rich because that metered air is escaping from the leak.

 

So would that mean it’s not a boost leak then since the car isn’t running rich under boost? When I ease past 3.5K and then go WOT the AFR is usually around 11.5-12, which is normal but when the violent jerking and hesitations happens it goes lean for that second.

 

I'd start looking at fuel, do you have a fuel pressure gauge? a clogged fuel filter, or a fuel pump on it way out, or even a fuel pump regulator... can you log throttle position is the curve smooth or does it cut out?