hello ClupLexus

My problem is:
that the car runs rich only when i restart it while its still warm. If i let it to cool down for like 45 minutes before restarting it will run great.
if i start it while its cold i can drive, it runs perfect. AFR around 14.5-14.9 at idle and around 14,1-14.4 cruising. i drove it 60 miles few days ago without turning off the engine and it kept on running perfect. once i turn it off and back on again while its still warm, it started idleing 11.8-12.2 afr. and i won't drive it like that to be on the safe side.

Temporary solution:
i installed Greddy emanage ultimate and used the widband for autotune and let it make adjustments to the fuel map. and that solved the problem. so whenever i restart it again i turn on the autotune and the emanage will start adjusting the fule to get to the targeted AFR.

but now i wanna figure out what makes it run like that. i want the engine to run good without having to have the emanage on the car.

Another weird thing that it does after restart is that it would go lean when i start to accelerate and go back to normal when i start boosting or when the RPM is above 3k.

Any ideas what could be wrong before i start spending money on replacing parts to try and figure out the problem

parts i changed to try to solve the problem:
Temp sensor. ( also checked the wiring for voltage and continuity )
o2 sensor. ( also checked the wiring for voltage and continuity )
checked for vacuum leaks but nothing is leaking.

parts i'm going to replace to try to solve the problem and why i'm suspecting them:

1. MAF sensor ( i tried to let the emanage run the engine without the maf. it does start normal like if the MAF is there but the problem is still there)
2. MAP sensor ( from researching and reading about this engine, everyone say that the engine depends on MAP just for the boost cut. correct me if i'm wrong)
3. ECU ( why not)
4. fuel injectors ( i thought they might be getting stuck open. but again when the emenage start trimming the fuel map it fixes the problem so i don't think that this is the problem but who knows )
5. fuel pressure regulator
6. recirculate the pov ( i read that this might cause it to run rich but not on idle..)



infos about the car








1999 GS300
2jzgte vvti
stock JZS161 ecu
single turbo borgwarner 60mm
3" downpipe to dual 2.5" no cat with new o2 sensor ( replaced it 3 times. the one that came with the GTE, Denso, and bosch )
FMIC with the maf on the cold side of IC ( closer to the TB)
AEM AFR gauge
walbro 255
boost controller set to14 psi.
PCV deleted and the intake manifold port for it is closed
K&N 4" filter ( i just took it off to take the picture but i actually have it on all the time )

sorry for any grammar mistakes. English is a second language for me

 

What was the reason you deleted the PVC system? I'm not to sure on the 2jzgte system, but on some systems the PCV valves emissions (HC blow by) is calculated as part of the A/F mixture during idling and light cruise. So if you have removed it, then the system may end up doing weird things.
What is the LTFT value?
And does the A/F ratio stay around 12:1 even after 5 - 10 minutes of starting the car when already up to operating temp? Or does it only stay at that ratio under 5 minutes or when you start driving?

 

Sounds like the car is going into open loop mode. By you moving the maf to a different location might be throwing the stock fuel tables out of whack. Thats why when you restart the computer see it as a problem and loads default tunes to compensate and richen the mixture!

 

Also by deleting the PCV system I hope you mean that you have installed a catch can.......otherwise that engine is a ticking timebomb!

 

yes i did put a catch can there and i put a cap on the port that are not used on the intake manifold.

but why would it do that only after restart. if i keep driving it for hours, without turbibg the engine off, it would act normal not rich not lean.

i forgot to say that its been doing that even before relocating it. But before relocating it it didn't idle correct at 14.7 on cold start. it used to idle at 16-17 on cold start when the maf was on the inlet of the turbo and then after restart it would drop again to around 12.


unfortunately the jdm GTE is not OBD2 i don't think i can check the LTFT. the pcv port was capped of so its not causing the problem for sure. and even if i let it run or drive it after restart it would still idle rich not even after 5 minutes


thanks guys , appreciate any help.

 

Solved !!

for some reason it was the temp sensor??
I went to visit a tuner in here and he told me that the it might be that the ecu sees the temp going up and starts running rich.
so i went ahead and replaced both the fan switch sensor and the temp sender thingy.
and now it runs great just like before.

 

 

Most people thinks they can't read CEL with JDM ecu, but in fact it can be pulled manually with dash light blink patterns or use Techstream under the Japan region.