AFR Running Lean

[Simo2007]

Evening Guys!

 

Hope you all had a good Xmas and all that carry on.

 

Recently went BPU- well, I still have a boost controller and FCD to fit but...

 

AEM Wideband is suggesting I'm running lean apart from WOT. Starting the car from cold, the AFR indicates 14.5 ish but then rapidly increases off the lean scale (17+) after about 10 seconds of running.

 

Seems to stay in this very lean region when cruising, bumps to 13-14 when on first turbo and at WOT it's constant at 10.1. I'd imagine a faulty coil pack may cause it to run in the lean spectrum (correct me if I'm wrong). Trying to get some more coil packs to test out my theory, but has anyone had a similar problem before by any chance?

 

5 of the 6 old plugs that came out looked like the left, 1 of the plugs was the right one- looks a lot darker than the rest!

 

Edited December 30, 2019 by Simo2007 (see edit history)

[Frank Bullitt]

Thats rich, rich is lower than 14, lean above 14

[Swampy442]

As above, whats the spec of the car?

[Simo2007]

As above, whats the spec of the car?

 

Which plug do you think is rich? The right one or both? My AEM wideband suggests I’m lean, shouldn’t I be 14 on idle, 11.5 ish on initial turbo and 10-11 on WOT (which I am on WOT)?

 

3 inch double decat

Fujitsubo backbox

Restrictor ring fitted

Wideband O2 sensor on second decat (inclined)

Stock turbos

NGK BKR7E (6097) gapped to 0.8mm

Walbro 255LPH fuel pump

Replaced coil clips

 

Everything else is stock mechanically, yet to fit the FCD (from Chris Wilson) and electronic boost controller.

[Frank Bullitt]

Did you see my post above?

 

Lean is any number above 14 on the AFR and any number below 14 is considered rich. The numbers you have quoted in all of your posts show you car is running rich not lean

[Simo2007]

Did you see my post above?

 

Lean is any number above 14 on the AFR and any number below 14 is considered rich. The numbers you have quoted in all of your posts show you car is running rich not lean

 

Hi Frank, yeah I did but I’m not quite sure how my post suggests I’m running rich. The only time it runs rich is at WOT which is 10.1, I understand everything under 14 is rich but on first turbo it should be running around 11.5 shouldn’t it? Which would mean I’m running lean on boost on the first turbo (relative to the 11.5) and on idle it shoots off to 17+ which is also lean.

[Boyne]

When you say shoots of to 17+ is this of or in boost, at gentle cruise I have often seen 16 which is excellent for fuel economy, however when on the throttle always lower from 15down to 10.5 or so.

[Sheefa]

Hi Frank, yeah I did but I’m not quite sure how my post suggests I’m running rich. The only time it runs rich is at WOT which is 10.1, I understand everything under 14 is rich but on first turbo it should be running around 11.5 shouldn’t it? Which would mean I’m running lean on boost on the first turbo (relative to the 11.5) and on idle it shoots off to 17+ which is also lean.

 

Shoots to 17 and above on idle or let off boost? Mine BPU used to always spike to lean when I let off the WOT pedal. Can you be more specific?

[Simo2007]

Thanks for the reply guys, as mentioned in my first post it shoots from 14.5 to 17+ after a few seconds from cold start.

 

Under normal driving conditions ie first turbo, off boost it’s off the scale at 17+ and under a bit of throttle to get the first turbo spooling at 1500rpm or so it comes to 15 ish and drops a bit further to mid 14 under more throttle until second turbo comes in and stays solid at 10.1 at WOT.

 

I believe relatively speaking the AFR under boost on the first turbo is running lean- I’m hearing 11-12 is normal and 10-11 on 2nd turbo WOT as it’s fuelling in open loop.

[Mike2JZ]

How new is your fuel filter?

 

What AEM gauge are you using, it is new? Is it new or old model that require free air calibration.

 

Do you have any air leaks present on your intake system somewhere.

 

Have you installed the fuel pump yourself?

 

AFR's should be in the following ranges, providing no HKS FCD is used and stock boost levels on stock ECU:

 

Cold Start: 11.5 -> 13.5 (Get's leaner as engine warms up)

 

Warm Idle: 14.0 - 15.0

 

First Turbo: 12.0-13.0

 

Second Turbo: 10.0-11.0

 

Off Throttle Coasting (Overun Fuel Cut): Fully Lean

[Mo Reviews]

How new is your fuel filter?

 

What AEM gauge are you using, it is new? Is it new or old model that require free air calibration.

 

Do you have any air leaks present on your intake system somewhere.

 

Have you installed the fuel pump yourself?

 

AFR's should be in the following ranges, providing no HKS FCD is used and stock boost levels on stock ECU:

 

Cold Start: 11.5 -> 13.5 (Get's leaner as engine warms up)

 

Warm Idle: 14.0 - 15.0

 

First Turbo: 12.0-13.0

 

Second Turbo: 10.0-11.0

 

Off Throttle Coasting (Overun Fuel Cut): Fully Lean

 

Wouldn't an air leak cause it to run rich rather than lean?

 

I had something similar happen on a previous Supra and it turned out to be a dud Bosch fuel pump, which turned out to be an easy fix. Therefore, my immediate hunch would be to check the fuelling system; fuel pump, fuel lines, fuel filter and injectors for issues then move on to the electrical side of the fuelling system. I.e. check the wires to the fuel pump for unexpected voltage drops and check the wiring loom going to the ECU for damage or kinks in the wires, as I have previously experienced issues arising from the same, albeit on aftermarket ECUs and harnesses but still worth a check...

[Simo2007]

How new is your fuel filter?

 

What AEM gauge are you using, it is new? Is it new or old model that require free air calibration.

 

Do you have any air leaks present on your intake system somewhere.

 

Have you installed the fuel pump yourself?

 

AFR's should be in the following ranges, providing no HKS FCD is used and stock boost levels on stock ECU:

 

Cold Start: 11.5 -> 13.5 (Get's leaner as engine warms up)

 

Warm Idle: 14.0 - 15.0

 

First Turbo: 12.0-13.0

 

Second Turbo: 10.0-11.0

 

Off Throttle Coasting (Overun Fuel Cut): Fully Lean

 

As far as I'm aware the fuel filter is new as of April this year.

 

I have an AEM Wideband gauge, with a Bosch 4.9 LSU sensor, as far as I'm aware it's pre calibrated and I'm running it on the linear calibration P00.

 

I have yet to check for air leaks but there are no obvious tears/splices in any of the vacuum lines.

 

I fitted the fuel pump myself, I thought the old one may be shot but the symptoms are exactly the same after the Walbro 255LPH 'upgrade'.

 

I have a spare set of coil packs now for testing (thank you Gaz) so this will be my first point of call tomorrow. I will report back!

[Simo2007]

Swapped the coil packs over today. No difference. I now need to investigate the vac lines.

 

Just on a random, would the earthing point for the AEM gauge inflict any problems? Would it be a good idea to match the ecu earthing point?

 

I need to check if there’s a FCD under the passenger carpet too.

 

I took some pictures of the vac lines, are there any other places I should pay attention to? There’s definitely been some form of boost controller or gauge plumbed in before!

 

[Mike2JZ]

Swapped the coil packs over today. No difference. I now need to investigate the vac lines.

 

Just on a random, would the earthing point for the AEM gauge inflict any problems? Would it be a good idea to match the ecu earthing point?

 

I need to check if there’s a FCD under the passenger carpet too.

 

I took some pictures of the vac lines, are there any other places I should pay attention to? There’s definitely been some form of boost controller or gauge plumbed in before!

 

https://jza80.mkivsupra.net/imports/2019/12/89.jpghttps://jza80.mkivsupra.net/imports/2019/12/90.jpghttps://jza80.mkivsupra.net/imports/2019/12/91.jpghttps://jza80.mkivsupra.net/imports/2019/12/92.jpg

 

Easiest way to detect air leaks is with a smoke tester. A local garage should have one. Can be difficult to tell the state of some rubber hoses unless they have been installed incorrectly, but looks to be in the usual places based off your photos.

 

I have seen similar symptoms to this when a HKS FCD has been setup incorrectly. Considering it takes 2 minutes to pull back passenger footwell carpet and remove ECU cover, I would prioritise that as your next step. Whilst you are there check your ECU is stock and not a modded ECU from the likes of Mines, Toms etc. Finally, check the wiring hasn't been messed around with too much whilst you are there.

 

AFR gauge grounding location would matter if you were using the 0-5v output on a standalone ECU as it can suffer from voltage/ground drops, but as you are just reading numbers from the gauge screen it won't make much difference where you ground it.

 

Try checking error codes. See if anything has been stored that might give you a hint.

 

Worth checking if you have any major air leaks in exhaust system pre 02 sensor, as this can cause false lean readings.

[Simo2007]

Easiest way to detect air leaks is with a smoke tester. A local garage should have one. Can be difficult to tell the state of some rubber hoses unless they have been installed incorrectly, but looks to be in the usual places based off your photos.

 

I have seen similar symptoms to this when a HKS FCD has been setup incorrectly. Considering it takes 2 minutes to pull back passenger footwell carpet and remove ECU cover, I would prioritise that as your next step. Whilst you are there check your ECU is stock and not a modded ECU from the likes of Mines, Toms etc. Finally, check the wiring hasn't been messed around with too much whilst you are there.

 

AFR gauge grounding location would matter if you were using the 0-5v output on a standalone ECU as it can suffer from voltage/ground drops, but as you are just reading numbers from the gauge screen it won't make much difference where you ground it.

 

Try checking error codes. See if anything has been stored that might give you a hint.

 

Worth checking if you have any major air leaks in exhaust system pre 02 sensor, as this can cause false lean readings.

 

Mike, thank you very much for your detailed response. I will crack on with the FCD check and error codes tomorrow tomorrow and get some stuff checked off the list as soon as I can!

[Simo2007]

Had another mooch around today and found something interesting. Well the not so interesting bit first... stock ECU and no FCD at all. I've got a Chris Wilson FCD to go in but no instructions to piggy back it onto the ECU, does anyone have them to hand?

 

Secondly, I've wired up an electronic boost controller. Target boost 1.2bar, overboost cut set at 1.24bar annnnddd... it won't boost over 0.7bar at all. Full decatted with a restrictor ring fitted (Whifbitz).

 

Specs again:

 

3 inch double decat

Fujitsubo backbox

Restrictor ring fitted

Wideband O2 sensor on second decat (inclined)

Stock turbos

NGK BKR7E (6097) gapped to 0.8mm

Walbro 255LPH fuel pump

Replaced coil clips

 

This is really pointing towards a vac leak isn't it?

[Mike2JZ]

Had another mooch around today and found something interesting. Well the not so interesting bit first... stock ECU and no FCD at all. I've got a Chris Wilson FCD to go in but no instructions to piggy back it onto the ECU, does anyone have them to hand?

 

Secondly, I've wired up an electronic boost controller. Target boost 1.2bar, overboost cut set at 1.24bar annnnddd... it won't boost over 0.7bar at all. Full decatted with a restrictor ring fitted (Whifbitz).

 

Specs again:

 

3 inch double decat

Fujitsubo backbox

Restrictor ring fitted

Wideband O2 sensor on second decat (inclined)

Stock turbos

NGK BKR7E (6097) gapped to 0.8mm

Walbro 255LPH fuel pump

Replaced coil clips

 

This is really pointing towards a vac leak isn't it?

 

Wiring for FCD is the same as Greddy FCD. For Non VVTI ECU, instructions are here: http://mkiv.com/techarticles/bcc/bcc_install/bcc-htm

 

If you aren't reaching your target boost then you could have one of the following issues:

 

a) You have plumbed up your boost controller wrong.

b) One or both of your turbo air filter joiner pipes have collapsed, causing a restriction. This can cause funky boost issues, or lack of boost issues.

c) Your second turbo is not coming online. First turbo normally only boosts to around 0.5-0.7. Try switching to TTC mode and see if this allows you to boost any higher. If so, then you need to diagnose your sequential system and see why second turbo is not playing ball.

d) Decent sized boost leak somewhere.

e) Your fuel system is borked and not delivering enough fuel to allow engine to produce any more puff. Last time I saw this happen, the car felt like it had an RPM limit around 4000-5000rpm where there wasnt enough fuel for second turbo to feel like it did anything.

[Simo2007]

Wiring for FCD is the same as Greddy FCD. For Non VVTI ECU, instructions are here: http://mkiv.com/techarticles/bcc/bcc_install/bcc-htm

 

If you aren't reaching your target boost then you could have one of the following issues:

 

a) You have plumbed up your boost controller wrong.

b) One or both of your turbo air filter joiner pipes have collapsed, causing a restriction. This can cause funky boost issues, or lack of boost issues.

c) Your second turbo is not coming online. First turbo normally only boosts to around 0.5-0.7. Try switching to TTC mode and see if this allows you to boost any higher. If so, then you need to diagnose your sequential system and see why second turbo is not playing ball.

d) Decent sized boost leak somewhere.

e) Your fuel system is borked and not delivering enough fuel to allow engine to produce any more puff. Last time I saw this happen, the car felt like it had an RPM limit around 4000-5000rpm where there wasnt enough fuel for second turbo to feel like it did anything.

 

Thanks for the FCD link Mike, I tried to find this earlier but the link was broken, I saw people say it's the same wiring as the Greddy not the HKS.

 

And yes, I'm a lemon, first time plumbing in the boost controller I got it wrong, at least it was boosting okay to stock levels! Put the inlet port on the solenoid to the front turbo, and the output to the upwards pointing port on the actuator, I believe that is correct now. Just need to cap off the two ports at the bottom like so (correct me if I'm wrong, and apologies, not my drawing)...