GS300 NA-T Running Terrible
08-05-17, 02:19 PM
#16
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Ok I will keep my eyes open for a good pair of used injectors. I don't mean to bring this topic back to yesterday, but the more I read up the more I don't think o2 sensors are my problem. I have both upstream o2 sensors plugged in and in place. Just my downstreams are unplugged. This can really cause terrible idle, terrible gas mileage, and.a rich condition??
08-05-17, 06:07 PM
#17
On the wires you cut, O2 sensor sometimes have stainless steel wires that are next to impossible to solder on even for an experienced solderer. You might need a whole other sensor, hopefully you didn't cut the half that's on the engine harness. Test this by starting up the car N/A when you get them back in and see if you get codes. Plug I believe is underneath the carpet on the passenger side IIRC
Now getting the rear O2 sensors running again is still only a beginning point. You might still have a check engine light from the factory ECU still trying to dump fuel, but hopefully it won't be as much. A tune would be able to control this a little better and perhaps rid the engine light.
Now getting the rear O2 sensors running again is still only a beginning point. You might still have a check engine light from the factory ECU still trying to dump fuel, but hopefully it won't be as much. A tune would be able to control this a little better and perhaps rid the engine light.
08-16-17, 04:23 PM
#18
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Yes it can and will. Why wouldnt you think not having two sensors plugged in that control AIr to fuel ratios in idle and under full throttle wouldnt affect things on a car let alone modified? Rhetorical question 
My post above even explained why it idles and cruises horribly but at wot it goes good
My post above even explained why it idles and cruises horribly but at wot it goes good
08-17-17, 08:01 PM
#19
I'm sorry to hear.
But that wire harness you cut, how did you manage to fix that part when you put a new sensor in?
EDIT: On second thought, you said you disconnected the charge pipe and ran naturally aspirated and still were running super rich.
DId you try clearing the computer to reset fuel trims before trying this? Did it bog down while driving NA? What would cause a car to run super rich? An air leak most likely, the ECU senses possible unmetered air and dumps fuel to adjust. Maybe you knocked something around but didn't set off the check engine light
But that wire harness you cut, how did you manage to fix that part when you put a new sensor in?
EDIT: On second thought, you said you disconnected the charge pipe and ran naturally aspirated and still were running super rich.
DId you try clearing the computer to reset fuel trims before trying this? Did it bog down while driving NA? What would cause a car to run super rich? An air leak most likely, the ECU senses possible unmetered air and dumps fuel to adjust. Maybe you knocked something around but didn't set off the check engine light
Last edited by GS400V8; 08-17-17 at 08:07 PM.
08-23-17, 08:16 AM
#20
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I'm sorry to hear.
But that wire harness you cut, how did you manage to fix that part when you put a new sensor in?
EDIT: On second thought, you said you disconnected the charge pipe and ran naturally aspirated and still were running super rich.
DId you try clearing the computer to reset fuel trims before trying this? Did it bog down while driving NA? What would cause a car to run super rich? An air leak most likely, the ECU senses possible unmetered air and dumps fuel to adjust. Maybe you knocked something around but didn't set off the check engine light
But that wire harness you cut, how did you manage to fix that part when you put a new sensor in?
EDIT: On second thought, you said you disconnected the charge pipe and ran naturally aspirated and still were running super rich.
DId you try clearing the computer to reset fuel trims before trying this? Did it bog down while driving NA? What would cause a car to run super rich? An air leak most likely, the ECU senses possible unmetered air and dumps fuel to adjust. Maybe you knocked something around but didn't set off the check engine light
08-25-17, 08:59 AM
#21
Now that Ive been driving my procharged GS400 around, I can share my insight on forced induction cars who werent originally.
You need a way to trick the ECU on your NA-T build. I have sucessfully tuned my car with only an Apexi neo. Because Im telling the ECU via the Apexi to cut fuel, or in consequence it thinks less air is going through, the ECU thinks the same amount of air flow is going through as it left the factory.
But with larger injectors and colder spark plugs, it is able to add the correct amount of fuel that only I know is going in, matching the right amount of air that only I know is going in, thus giving me huge power.
Basically your ECU is freaking out right now and you need a way of medicating it via computer trickery. I highly reccommend the 310cc injectors as I mentioned in my earlier posts.
Also do you have a bypass/diverter valve,
The diverter valve really helps at idle or anything below full throttle. It bypasses alot of the boost. That compared with the nature of a turbo (and my centrifugal) where they dont make alot of boost down low, makes for an easy tune. Less boost + bypassing some of it (to the air or into your intake like mine) = easy tuning because the air flow isnt any different than stock.
You need a way to trick the ECU on your NA-T build. I have sucessfully tuned my car with only an Apexi neo. Because Im telling the ECU via the Apexi to cut fuel, or in consequence it thinks less air is going through, the ECU thinks the same amount of air flow is going through as it left the factory.
But with larger injectors and colder spark plugs, it is able to add the correct amount of fuel that only I know is going in, matching the right amount of air that only I know is going in, thus giving me huge power.
Basically your ECU is freaking out right now and you need a way of medicating it via computer trickery. I highly reccommend the 310cc injectors as I mentioned in my earlier posts.
Also do you have a bypass/diverter valve,
The diverter valve really helps at idle or anything below full throttle. It bypasses alot of the boost. That compared with the nature of a turbo (and my centrifugal) where they dont make alot of boost down low, makes for an easy tune. Less boost + bypassing some of it (to the air or into your intake like mine) = easy tuning because the air flow isnt any different than stock.
09-01-19, 04:08 PM
#22
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Start up problems
I have a 1998 gs300 Lexus I went and had codes read they said it was mass flow air censor so I replaced it also replaced air filter it will start up most times but out of the blue it will act like its gonna start but won't fire up can someone help plz
09-05-19, 06:59 AM
#23
Sounds to me like you just need tuning. You mentioned you have an aftermarket FPR. Have you tried adjusting it? I happen to have an AFC Neo and plug and play harness for sale in the marketplace. Let me know if you want it. Brand new and saves a few hundred off new price.
01-17-21, 02:06 PM
#25
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I had the same problem ! Very long cranking at start up no power low to mid range Bog, I hooked up a voltage meter under the seat I was only getting 8v at the fuel pump. and 12v at WOT I purchased a used fuel pump Ecu I got 8v then 9.5 with lite pressure on throttle 12 to 14.5 at wot Engine ran much better but still had a slight bog under acceleration since I also had replaced the fuel pump it felt like fuel starvation . So I removed the pump and found the O-rings were not sealing tightly on the regulator causing fuel to escape without passing through the regulator! I also removed the fuel ecu and jumped the wires just to test and the car instantly started every time Hope this helps someone diagnose there problem Also after changing the timing belt I started it up and it was running rough I couldnt figure out why al Idlel I did was loosen the tps sensor moved it left and right and set the engine idle it ran fine after that Good luck!!
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