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25det having some AFR issues

StressedPoet654
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StressedPoet654 Apprentice

StressedPoet654

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Heya guys hope everyone is managing to pull through this pretty shit time we're all going through. Sorry for the massive write up in advance just wanted to try to fill in as much info as i can and also log it somewhere i guess. Anyways, so for a long time now I've had a lot of inconsistencies with the performance of my car which I've always had a feeling was it either running rich or lean, so finally got a wideband and installed it ect. At cruising its around 14.5afr, then when I give it some throttle it drops to a rich 12ish, but most of the time as the boost builds up, it starts to lean out (ill normally get right off the throttle as soon as I notice it getting towards 14 as I can feel it lacking in power and it goes upto 15 before I'll let off. Just easing off the throttle the afr drops back down to 13-14 but its still definitely not feeling right as I cant go push more than 1/4 throttle before it'll lean out a bit. Will def keep climbing upto around 16.5afr if i keep it wide open but obviously I don't let it, only once for testing purposes)

BUT** 1 in 10 times it will drop to around 11.5 afr and then only go up to 12.5 and stay around that afr once its at full boost while the revs go up. At this point it pulls super well just like it should. I'm really not sure whats causing it to keep going lean but then sometimes be absolutely mint.
Car info: S2 25det, r32 currently on about 11psi
Chipped Z32 ecu and green sticker afm. 550cc injectors 290lph fuel pump, cut and shut intake, top mount turb, big intercooler, fairly new coils, turbosmart 38mm gate, t-s boost tap. These are the main mods its got, which I don't expect to be cuaing problems.

Things I've done so far to troubleshoot are: run ecu codes (code 55 so nothing) change spark plugs and gap to .7mm , check coils and TPS with voltmeter (all were normal and in spec), checked for faulty CAS (not faulty), changed fuel filter changed, changed VCT solenoid (VCT is not working, but I'm not sure if it's because the ECU is not running it or if there is a problem elsewhere there is 12v to the solenoid but haven't checked to see if the ground switchis getting triggered) clean afm, check and clean injectors all were sweet, check for boost leaks (tiny one on a fitting but i really don't think it's bad enough to cause any problems as it was almost barely noticeable.) Most of these were checked before I had the wideband installed ad I didn't know what exactly was causing my lack of power (which is now obviously lack of fuel)

Again sorry for this huge writeup of a hopefully stupid easy fix of something I just haven't thought of being the problem yet. I'll make some changes if I remember anything and I'll have to come check in the morning for any replies. Cheers guys.

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https://www.sau.com.au/forums/topic/480077-25det-having-some-afr-issues/
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StressedPoet654 Apprentice

StressedPoet654

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Thanks for the comments and sorry for the delay, that small boost leak i mentioned should now be fixed. I'll have a look at the fuel pump and check for any visible wiring issues with it tomrrow when i have a bit of time. Wiring is all standard. I'll do some research and try to find a way to test it unless someone replies with a good method before I get to doing it. Also had a thought could it be the fuel pressure regulator maybe? I'm pretty certain that the afr wideband is working 100% correctly as I can feel with the car when its starting to lean out and when its not.

Kinkstaah Grand Master

Kinkstaah

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Is it exactly the same scenario when the car leans out? Not only between 60-80% throttle? Not only under 90C water temp? Not only when Sensor X is doing Y?

It could be tune related.

Putting it on a dyno after checking everything mechanical (and allowing yourself to see things like fuel pressure while the car is on the dyno under load) will help.

If you DO have fuel pressure, but running lean...

GTSBoy Grand Master

GTSBoy

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59 minutes ago, StressedPoet654 said:

I'll have a look at the fuel pump and check for any visible wiring issues with it tomrrow when i have a bit of time

This (the visual inspection) is worth nothing compared to having a fuel pressure gauge on it when it goes lean. Easier on teh dyno, like Kinkstaah said above.

StressedPoet654 Apprentice

StressedPoet654

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48 minutes ago, GTSBoy said:

This (the visual inspection) is worth nothing compared to having a fuel pressure gauge on it when it goes lean. Easier on teh dyno, like Kinkstaah said above.

Yep I know, just don't have access to a guage and won't until the lockdown in NZ is over. 

StressedPoet654 Apprentice

StressedPoet654

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57 minutes ago, Kinkstaah said:

Is it exactly the same scenario when the car leans out? Not only between 60-80% throttle? Not only under 90C water temp? Not only when Sensor X is doing Y?

It could be tune related.

Putting it on a dyno after checking everything mechanical (and allowing yourself to see things like fuel pressure while the car is on the dyno under load) will help.

If you DO have fuel pressure, but running lean...

No matter what, whether the car has been running for 30 mins or 5 mins, other than the odd few occasions anything more than about 60 or 70% throttle it will start to lean out on boost, if I slightly let off the afr will drop and it'll start to pull a bit more normally, but at that 50% or less throttle. I know a few people with one but I don't know if I'll be able to get a fuel pressure guage until the lockdown is over

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