Sr20det extremely lean all of a sudden

[Rocketbunny240sx]

Hey guys my sr20det redtop in a s13 hatch has been running extremely lean out of no where it slowly got there. My afr gauge used to be at the 14-15 range then it went to the 16-17 range and just today went to 19 and 20 the gauge even saids lean once a while now. When i boost it, it runs fine it will boost away no problem. I thought it may have been a boost or vac leak some where cant seem to find any. And i just had new plugs gapped to .32. Ive got a supra twin turbo fuel pump 390lph and i have 750 cc nismo injectors. My fuel pressure is set to 40 psi. Im also running a fuel management system so no iacv. Need help anything works! Thanks!!

I forgot to say it was only at idle it leans out. It will go from 14 ish and then all the way down to 17-19

[blksylv]

any exhaust leaks?

[Rocketbunny240sx]

I'll check but i didnt hear any

[jr_ss]

Better yet, do you have a tune?

Have you tried a free air calibration for the sensor?

[Rocketbunny240sx]

Yeah but it has been a while since ive last tuned it. Why would that make it run lean tho? Ecu can reset ?

[Kingtal0n]

walking lean at idle is a sign of bad O2 sensor. disconnect it to diagnose.

[Rocketbunny240sx]

Originally Posted by Kingtal0n

walking lean at idle is a sign of bad O2 sensor. disconnect it to diagnose.

My car afr gauge runs off the o2 sensor. The o2 is directly connected to the afr gauge and then the gauge is directly connected to me ecu.

[Kingtal0n]

Originally Posted by Rocketbunny240sx

My car afr gauge runs off the o2 sensor. The o2 is directly connected to the afr gauge and then the gauge is directly connected to me ecu.

I Have no idea what you just said and it only makes me that much more suspicious that this is related to your problem.

[Rocketbunny240sx]

Originally Posted by Kingtal0n

I Have no idea what you just said and it only makes me that much more suspicious that this is related to your problem.

Im saying my air and fuel ratio gauge is connected directly to my o2 and my ecu connects to me air fuel ratio gauge. On my air fuel ratio gauge theres 2 wires and ive followed them. And thats what i found

[zurud]

You need to rephrase your statement. I don't think anybody understood you.
Do you have wideband o2 ?
What is your "fuel management"?

[jr_ss]

Your AFR gauge has an wideband O2 sensor. If your gauge is hooked to your factory narrow band O2, that is not an accurate means of measuring your O2 reading. If it is indeed a wideband, you should pull it from the exhaust and do a free air calibration on it, if applicable. Your wideband should be connected to the ecu for feedback, so the engine management can see what your AFRs are doing, should your ecu have some type of auto-tune feature.

[Rocketbunny240sx]

Originally Posted by zurud

You need to rephrase your statement. I don't think anybody understood you.
Do you have wideband o2 ?
What is your "fuel management"?

Fuel management system basically my ecu is trying to idle on its own without a iacv so that has been completely taken out. It uses the mad and o2 to set the car at the lowest possible rating. So that it wont be fricken rich as fk while idling and when boosted it still can deliver super rich fuel. Altho i do have to support it once a while while pulling out of gear or down shifting because it stalls quite easily the idle will sometimes bounce for 1200-2000 and then it will stabilize itself.

[Rocketbunny240sx]

Originally Posted by jr_ss

Your AFR gauge has an wideband O2 sensor. If your gauge is hooked to your factory narrow band O2, that is not an accurate means of measuring your O2 reading. If it is indeed a wideband, you should pull it from the exhaust and do a free air calibration on it, if applicable. Your wideband should be connected to the ecu for feedback, so the engine management can see what your AFRs are doing, should your ecu have some type of auto-tune feature.

I tried to take my o2 sensor out yesterday and ran my car. It richened itself but i didnt try driving with that because i didnt think it was a good idea. Does that mean it was my o2? I tried searching for leaks with carb cleaner and i sprayed it at my hoses like vaccum hoses and all my turbo hoses ect. Idle didnt got up.

[zurud]

Sorry dude. You are on your own. You mess with your car. Only you know what is going on with it. Nobody pull their IACV. I hope you know what you are doing. Are you trying to be mad scientist or something. ?

[Rocketbunny240sx]

Originally Posted by zurud

Sorry dude. You are on your own. You mess with your car. Only you know what is going on with it. Nobody pull their IACV. I hope you know what you are doing. Are you trying to be mad scientist or something. ?

Naw it was made to be a track car but i daily it. I heard it was better to fuel management than iacv apparently makes the car lighter and faster?

[jedi03]

Lol I have seem several people who pull theirs...my understanding is its supposed to help it warm up...idle air control valve...the 02 per enthalpy will help with economy, I'm gna replace mine today as mine went lean after 2 years of no issues. I halfway suspect bad fuel for me but I will see!

[Rocketbunny240sx]

Do you guys think it could be my maf?

[Kingtal0n]

Here is nutshell SOP
1. Install all OEM parts including IACV
2. compression test, boost leak test, tune up: oil/filters/clean the maf/ clean the inlet (wash all plumbing thorough with degreaser and water) wipe everything completely dry before using it again.
3. Disconnect the narrowband oxygen sensor and drive the car. Does it drive normal? You do not need to boost the engine to drive the car normal.
4. Once you see whether the narrowband was fooling the ECU you can replace the O2 sensor, or start changing other parts i.e. maf/ecu/regulator/fuel pump with the fuel pump being next on the list for sudden lean issues besides narrowbands.

[Rocketbunny240sx]

Originally Posted by Kingtal0n

Here is nutshell SOP
1. Install all OEM parts including IACV
2. compression test, boost leak test, tune up: oil/filters/clean the maf/ clean the inlet (wash all plumbing thorough with degreaser and water) wipe everything completely dry before using it again.
3. Disconnect the narrowband oxygen sensor and drive the car. Does it drive normal? You do not need to boost the engine to drive the car normal.
4. Once you see whether the narrowband was fooling the ECU you can replace the O2 sensor, or start changing other parts i.e. maf/ecu/regulator/fuel pump with the fuel pump being next on the list for sudden lean issues besides narrowbands.

I had my fuel pump changed not more than id say 3-4 months ago ? Im running a supra twinturbo 390lph fuel pump.

[Kingtal0n]

Originally Posted by Rocketbunny240sx

I had my fuel pump changed not more than id say 3-4 months ago ? Im running a supra twinturbo 390lph fuel pump.

A used 16 year old OEM fuel pump with 150,000 miles on it from the first owner, and 50k on it from a second owner? Or you dropped more money on your fuel pump buying a new one than your engine is worth. Either way, I don't make the rules. It could be fuel leak, a ruptured ancient fuel in the tank that finally popped maybe your re-used 18 year old fuel lines with presumably all this pumping power.

[Rocketbunny240sx]

Originally Posted by Kingtal0n

A used 16 year old OEM fuel pump with 150,000 miles on it from the first owner, and 50k on it from a second owner? Or you dropped more money on your fuel pump buying a new one than your engine is worth. Either way, I don't make the rules. It could be fuel leak, a ruptured ancient fuel in the tank that finally popped maybe your re-used 18 year old fuel lines with presumably all this pumping power.

My fuel lines are all like the russel steel pipes so its a very low chance