AFR of ~15 during throttle but up to 20.3 off throttle, idles at ~15 ok?

[tracerit]

I have a Unichip and turned it off on Tuesday morning, drove ok that night. However on Wednesday night when I started the car it hesitated a bit, check engine light came on and I turned it off. Used my Torque app and discovered the P0102 code. Turns out Mass airflow Circuit Low. I checked the MAF and all hoses and it turned out ok. Cleared the code. Drove it to work.

Then tonight I used Torque to check the AFR during my drive. At an idle stop it's ~15, on throttle it's ~15 but when I let off throttle it'll jump up to 20.3, then back to ~15 when I come to a stop. Is this normal?

[Hawaiian]

Originally Posted by tracerit

I have a Unichip and turned it off on Tuesday morning, drove ok that night. However on Wednesday night when I started the car it hesitated a bit, check engine light came on and I turned it off. Used my Torque app and discovered the P0102 code. Turns out Mass airflow Circuit Low. I checked the MAF and all hoses and it turned out ok. Cleared the code. Drove it to work.

Then tonight I used Torque to check the AFR during my drive. At an idle stop it's ~15, on throttle it's ~15 but when I let off throttle it'll jump up to 20.3, then back to ~15 when I come to a stop. Is this normal?

Short answer, yes, but i've been drinking and probably won't give a solid long answer. It's something to do with the limits of your sensor (20.3) and air passing through the engine when not under throttle.

Yay whiskey!

[jflogerzi]

Originally Posted by tracerit

I have a Unichip and turned it off on Tuesday morning, drove ok that night. However on Wednesday night when I started the car it hesitated a bit, check engine light came on and I turned it off. Used my Torque app and discovered the P0102 code. Turns out Mass airflow Circuit Low. I checked the MAF and all hoses and it turned out ok. Cleared the code. Drove it to work.

Then tonight I used Torque to check the AFR during my drive. At an idle stop it's ~15, on throttle it's ~15 but when I let off throttle it'll jump up to 20.3, then back to ~15 when I come to a stop. Is this normal?

20 with zero throttle is pretty normal. Best way to check AFR is start @ 2500RPM in 3rd. Do a pull WOT till red line. Whats your AFR there. Should be in the low to mid 11's

[zooki]

When you let off the throttle the car cuts off the fuel to the motor. Your basically just pumping air through it while you decelerate.

[86-tundra]

Originally Posted by tracerit

I have a Unichip and turned it off on Tuesday morning, drove ok that night. However on Wednesday night when I started the car it hesitated a bit, check engine light came on and I turned it off. Used my Torque app and discovered the P0102 code. Turns out Mass airflow Circuit Low. I checked the MAF and all hoses and it turned out ok. Cleared the code. Drove it to work.

Then tonight I used Torque to check the AFR during my drive. At an idle stop it's ~15, on throttle it's ~15 but when I let off throttle it'll jump up to 20.3, then back to ~15 when I come to a stop. Is this normal?

you do not want to have 15 AFR under WOT... not sure if that's what you're saying your seeing

[mitosis]

Originally Posted by trevorovert

you do not want to have 15 AFR under WOT... not sure if that's what you're saying your seeing

Yeah I've noticed that under partial throttle the car usually stays around 14.5, so it's hard to tell what the OP means by "on throttle" ...WOT or not? As others have stated, when giving zero throttle and coasting while still in gear the AFR is technically infinity (some quantity of air / zero fuel = divide by zero error, aka infinity) so that 20-ish that you're seeing is just the max value the sensor is capable of.

[tracerit]

it's not exactly 15, a bit under it. I was using the graph portion of Torque so i'll try again when I head to work and look at actual numbers while on cruise control to try and keep it consistent. it's not WOT btw, just a moderate amount of throttle? basically I don't drive aggressively is how I would describe my driving, I shift at 4k pretty much all the time.

[tracerit]

didn't want to create a new thread for this but when I was checking tubing I noticed this small collection of fluid right on top of the engine. Not sure where it came from, any ideas?

[Grip Ronin]

probably just some crap from outside got up there and pooled. no fluids travel up there from the car

[tracerit]

yeah it looks like maybe old rain water or moisture from the mornings when i think about it.

seems like the check engine light p0102 came from me turning the unichip on/off, so i'm thinking maybe it's the ECU accounting for the sudden change.

[86-tundra]

Originally Posted by tracerit

it's not exactly 15, a bit under it. I was using the graph portion of Torque so i'll try again when I head to work and look at actual numbers while on cruise control to try and keep it consistent. it's not WOT btw, just a moderate amount of throttle? basically I don't drive aggressively is how I would describe my driving, I shift at 4k pretty much all the time.

you need to go WOT for us to fully understand your issue. It's too hard to diagnose if you shift at 4k.

put it in 3rd, get low in the RPMS, and floor it. Just watch the AFR. Make sure it doesn't creep.

[jamesm]

11-11.5 afr is pretty damn rich for an NA car. That's what I run under boost .