Vacuum Leak or Tuning Issue?

[T4RunnerSteve]

Hey guys --

I recently installed my TRD Supercharger as described in this thread -- http://www.toyota-4runner.org/3rd-gen-t4rs/264025-supercharger-bust.html and am having an issue where once the truck warms up it idles rough at really high AFRs (18+). I am running larger injectors (380cc) and it runs nicely when I'm on the throttle (even slightly on the throttle) but the idle is so bad it:

1) Throws the P0171 code
2) Sometimes stalls

I have an appointment w/ a tuner next week to tune the AEM FIC-6 (it's running all 0s now -- no skewing) but am worried that I have a vacuum leak I should be fixing prior (so as not to waste tuner / dyno time). ST and LT fuel trims when idling are at like 15-20% (ouch) I cleaned the MAF sensor well and tried the propane trick to see if I could detect any vacuum leaks -- nothing from my attempt at that.

What do you guys think?

Thanks as always!
-Steve

 

[gamefreakgc]

A P0171 is one of three things:

1. Bad Oxygen sensor
2. Bad MAF
3. Vacuum leak.

Your wideband is telling you there actually is too much oxygen in the exhaust, so you can rule out #1. A bad/dirty MAF is possible, but if it worked just fine before the install I highly doubt you broke it. Unless you dropped it 6 feet onto the concrete like I did with mine (doh). Vacuum leak is the most likely cause. Make sure the supercharger is sitting level and all the bolts are tightened down. I find that the FSM specs on the intake manifold are not tight enough for the supercharger since it likes to lean on one side towards the engine hanger.

Also make sure the throttle body gasket surface was clean, sometimes the old gasket likes to fall apart and stay on, then it creates an air gap. Might also be good to double-check the vacuum hose routing so that you're not accidentally exposing it to atmospheric pressure.

And you are right, do not take it to be tuned until you fix that AFR. The tuner might just send you home.

 

[T4RunnerSteve]

A P0171 is one of three things:

1. Bad Oxygen sensor
2. Bad MAF
3. Vacuum leak.

Your wideband is telling you there actually is too much oxygen in the exhaust, so you can rule out #1. A bad/dirty MAF is possible, but if it worked just fine before the install I highly doubt you broke it. Unless you dropped it 6 feet onto the concrete like I did with mine (doh). Vacuum leak is the most likely cause. Make sure the supercharger is sitting level and all the bolts are tightened down. I find that the FSM specs on the intake manifold are not tight enough for the supercharger since it likes to lean on one side towards the engine hanger.

Also make sure the throttle body gasket surface was clean, sometimes the old gasket likes to fall apart and stay on, then it creates an air gap. Might also be good to double-check the vacuum hose routing so that you're not accidentally exposing it to atmospheric pressure.

And you are right, do not take it to be tuned until you fix that AFR. The tuner might just send you home.

Thank you. This is what I suspected -- I appreciate the feedback! Will let you know what I find --

 

[T4RunnerSteve]

Thank you. This is what I suspected -- I appreciate the feedback! Will let you know what I find --

Well... leave it to these wonderful communities to help fellow Toyota owners out: this post on Tacoma World depicts my exact problem / source of the vacuum leak. Plugged that and it idles warm right around 14.8 AFR. A step in the right direction and I now have a truck ready for tuning

Thanks again guys!