Lexus IS250 carbon buildup

So got to wrenching on the IS250 and did a mod I've been imagining for a long time. First backstory for the un-initiated:
The IS250 suffers from detrimental carbon buildup on the intake valves, to the extent it causes rough idles at first, then even stall-outs. Eventually Lexus extended the warranty and does whole new engine rebuilds to install a new piston design meant to 'fix' the issue- IMO it just shows it down.
The issue is due to not having port injectors, the nasty crank case junk bakes onto and builds up on the valves.
Idiot article that doesn't explain the issue well, but tries.

NOT MY CAR- interwebz pic


Mitigation is to use a catch can (already installed) and get the engine rebuild (already done). I feel like the buildup is still happening (studder when coming to a quick stop). In hindsight, just venting the crank to atmosphere is probably the best thing to do (Cali CARB, look away).

So one day googling around I find that the is250 has a 7th cold start injector due to direct injection cold start drama I guess- funny how old stuff comes back around. My excitement was that ''ah ha!" I can hijack that injector to inject when cruising on the freeway, the OEM ECU will learn around it and lean back to stoich and I will be cruising with "port injection" supplementing the direct injection simuliar to the is350 (hense it does not have the issue and tsb). Furthermore after looking at the injector I'm thinking its more a "7th fuel injection valve" as some old cars would put it- its not built to duty cycle but just on/off.

Finally got some parts in to test this on DISCLAIMER- if u have a lot of build up and do this you could break off chunks or carbon and get into the combustion, maybe even score the cylinder!!!

Whipped up a harness and switch and promptly stalled the motor at idle- so for sure this thing puts out more fuel than I initially suspected (had thought this just supplements the direct injectors during cold start).

'y'ed the ground side of the injector extension harness I made so I could run it to a switch in the cab, that was wired to a bolt behind the dash for ground.











Some driving at speed and yep, it dumps the fuel and you get that nasty cat smell u often get after doing WOT runs on newer cars.

So with it dumping way more fuel than I thought, I have a few more things to do:

- use my oscope to see if it's not an on/off injector.
- Pair my torque app and get the A/F pid working to see what numbers this things puts out when on.
- Find a cheap DIY way to pulse width to the 7th if the injector is pulsable- possibly an adruido with a simply on trigger and mosfet to drive the injector at some small rate that I switch on when cruising on the freeway.
- stop d*cking around and just vent to atmosphere- but still need a way to clean the valves up- too lazy to do a top clean service.

 

I've been a combination busy, or out of town or sick and haven't scoped or simply LED'd the 7th injector to see what scheme they use. Results will dictate the 'sop' I go with, be it on/off on freeway pulls or some kind of injector driver module.

 

What year IS is it? Must be before the 14+ I assume? My 350 (16) has port and direct injection, like the 3rd gen taco I think. Basically eliminates that issue.

 

2005, first year with purely direct injection. The easy thing to do is just vent crank to atmosphere but I want to nerd out on this a bit and have a way of cleaning off past buildup.

Yeah lots of DI out there without the issue, be it combo DI and port, or OEM style catch can/filter like setups, innovative valve timing etc. But also lots of early adopters that have been burned. The car is great otherwise- I would buy and mod to fix the issue vs not buy at all.

 

So I got side-tracked with a new issue, codes:
p2714 Powertrain- Pressure Control Solenoid D performance or stuck off
p2757 Powertrain- Torque Converter Cluth Pressue Control Solenoid Control Circuit Performance or Stuck Off

Really hoping just a really good flush will resolve this issue as it was intermittent at first until getting to where the car cannot shift beyond 4th. Sitting at a shop now that has the flushing equipment for these stupid "life time sealed" transmissions with fear the pan will need to be dropped and a solenoid or two will need to get replaced as well.

I've been convinced for some time that the newer Yotas are just not build like they used to be and this is solidifying that opinion.

I figured a trans cooler would help reduce the wear on the fluid and make the intervals go muuuch longer like on my truck, but these stupid things have a puck style cooler so there is no way to intercept lines to the radiator for a cooler.

 

Update:

Tranny had to be rebuilt.

Did my spark plugs and took some pics (will update post when from phone), carbon was building up again- slowly, but again.

Update 2:

Converted catch can to atmospheric vent system, plugged the intake port for it. Found A LOT of build up on the TB, this affected idle. So that means at higher load there was enough blow-by that fumes were being pushed into the intake part pre-TB and gunked up the TB.

Added to this, made a small "bypass" with restriction to simulate the MAF metered air flow that would go through the PCV system and into the manifold. This was necessary to get the drive by wire TB back into a good zone for it's fuzzy logic for idle control without CELs.

Result:

PCV intake port capped off, intake track capped off. PCV to manifold now goes to catch can vented to atmosphere. Carbon build up can go f*ck off.

 

Bored and browsing, found this thread. I had a 09 is250. Got my engine rebuilt under the tsb. Got the car back and about 8 months later the trans started going out. Got rid of it when the trans started going.
Lexus really missed the mark with the early is250's.
I will say i like the rcf

 

Yeah man, 100% this. Car has not one but at least two "fatal flaws" (as some youtubers would call it). At least the carbon thing can be mitigated somewhat, be it a great catch can and/or venting to atmosphere (have to make a 'tuned' air bypass cause the TB cannot compensate if you go vent to atmosphere). Plus there is a huge selection of carbon cleaners for DI cars now- use every oil change and it should help. Have to add though, venting to atmosphere kind of sucks as those fumes find their way into the cabin, especially if the air is not set to recirc (and this is already going through a catch can first).

One other thing I guess I didn't mention, the OEM head unit is soft too. Mine died along with a friends, replaced it with a Android unit that is meh. Can't believe how... domestic... Lexus has gotten.

But the transmission IMO is not fixable. Not so much IMO but the opinion of the shop that rebuilt it for me. That shop has a relationship with transgo and the owner was saying how lots of other trans can have factory flaws but transgo will fix it. For example maybe an OEM rod is aluminum and wears out really fast or starts to deform, transgo's rebuild kit will make that rod out of a better metal that doesn't wear out but also doesn't then cause some other part to wear out. They address the known issues a family of trans have. But in the case of the IS250, its a PWM type solenoid and the PWM control is janky, it makes the solenoid "shake" too much while holding a partial position. You can replace the seals with the highest of quality but its still going to wear out far sooner than a rebuild should. Add to this I couldn't do my standard issue 'ish I do with auto trans and install an additional aftermarket cooler- this cooling system is the coolant fluid to trans 'hockey puck' style, so there is no kit out there to potentially increase the trans life via additional cooling.

Maybe an ECU reflash could fix this- I've seen forum posts about IS250 shift TSB re-flashes but I can't find the actual TSB number or description. I called the local Lexus to check it out and they want a super high diagnostic fee as a gatekeeper just to look into if there is a TSB and if my car is applicable. Fug it, just going to get some couple tens of thousands of miles out of this one as an ROI and move on.

Big big scar on Toyota. I'd still get a 2nd a 3rd gen Taco and maybe their later model 4 runners but I can't be certain their other models are not totally compromised with fatal and un-mitigatable flaws. And honestly I look at 3rd gen Tacos only because they are good looking and still have a lot of support (like Supercharger, HPtuners, countless bumpers, suspension etc) but also due to lack of competition. If other OEMs can finally get themselves a product that actually competes, I'm all ears cause I'm pretty done with the "new" Toyota it has become. I'm keeping a lookout on Raptor Ranger news.

I know OEMs can't be perfect so I'm still cool with a model/platform when there is a solution to a known problem, but this trans thing is a hard-no. So pissed that as a die hard Toyota fan I'm now looking outside to other manufactures.

 

By far one of the slowest cars have ever had the opportunity to drive.

 

It was painfully slow
At the same time i had the is250 i had a 09 g37, never went head to head or compared numbers but it felt like the g37 blew the doors off the is250
The is250 definitely had more comforts tho