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Discussion Starter · #1 ·
please read all of it. i have to explain some things just so you know all of the info.

im having a problem with my lesux afm.
Dont have a WALBRO or AFPR... i did drill out the j-tube tho and didnt help anything and also did the 12V mod and didnt do anything.
i have 550's/lex, all the other basic shit, 61trim turbo, AEM Wideband too. I also just tonight acquired an old apexi safc (knob one) it goes like 800rpm, 2400, 4000, 5600, 7200 to adjust it. and i installed it tonight and doesnt make much of a difference.

i have been having a problem with the lexus afm, im not sure whats going on and cant figure it out and have made a couple threads on here but not many people say much becuase i prolly didnt tell the whole story and all the details.

the Story:
ok, a long time ago my stock afm sensor got wet and took a crap.
i bought a full Lexus AFM with sensor for 130 and got it the next day overnight shipping.
well i didnt have 550's then and just took the sensor off and put it on the stock afm. Ran Perfect...

ok, then i finally get the 550's and i install the lexus afm with the same sensor that came on it. i drive it around and it sputters with normal exceleration anywhere between 10%-80% throttle. dont know why...well when i go 100% throttle it doesnt sputter at all.

well then i get mad at it and decide to put my stock afm back on with the SAME sensor. runs Perfect and no sputtering at all but can only run 9psi instead of 16psi-? that i could run before.

well then i buy a AEM WIDEBAND and have the stock AFM on.
I notice that when im driving normal its not at the 14.7 (Stoich) area just cruising around its suppose to be. cant remember what its at right now. But its RICH and when i boost it goes to 10.0 or below.

so i decide to put the LEXUS back on and see what it reads. -----------------------PROBLEM READ THIS!!

so i drive around and i notice that when it ---Sputters it reads lean..15-18 sometimes just driving,---- but when i start Boosting it goes down fast and when i hit around 3-16psi it goes to 10.0 or below. now thats just gradualy going into the gas to WOT.

well when im driving and then just put it 100% throttle it doesnt sputter and doesnt read 15-17 on the wideband but it goes to only about 12 and when i start boosting it goes to 10.0 or below.

Also it never stays at STOICH. when im just cruising and stay at a set RPM at whatever MPH it will read about 11-12.4.

Also when i disconnect the O2 sensor and have the LEX on it runs fine and wont sputter at all and boosts fine and doesnt run so rich and doesnt run lean at all but still doesnt ever go stoich.

What is Going on!?!?! Its driving me insane and i dont know whats going on.
please help me!
could it be a bad afm? could it be a bad O2 sensor?
will an O2 sensor from a non-turbo work on a turbo?
 

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Spoolme, not sure if you've tried this or not yet - it sounds like you may need to make adjustments to the air screw in your Lex AFM. I had to do this to mine. I had some various sputtering, etc., and adjusted the air screw based on throttle response (probably not the best method, but it's been working great for over a year). Basically, I would give the throttle (by hand or by foot) a sharp jab to full throttle (or close). This would cause a bit of hesitation before the engine revved (kind of like with an old carbureted engine when you give it too much throttle too fast). I adjusted the screw until this didn't happen any more.

When I did the adjustments this way, I didn't have a wideband; but since you've got one, you should be able to monitor your changes with it. If your screw isn't opened up already, just drill out the plug (it's not very thick, so don't drill too deep!). Don't know for sure if this will cure your problem, but hopefully it will help you some. :)
 

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Discussion Starter · #3 ·
well i had it backed out all the way and it was worse and then i put it all the way in and the sputtering wasnt as back but is still there quite a bit. Its not just when i push the gas theres not a hesitation, its like the engine is missing it feels like when driving.
 

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in that case, it sounds like you may be correct thinking it may be your o2 sensor. From what I understand, your A/F should be rich using the stock AFM w/ the 550s - but when you put the Lex AFM on, it should normalize the A/F. But from your first post, it looks like it runs rich, until you press the throttle?

so i drive around and i notice that when it ---Sputters it reads lean..15-18 sometimes just driving,----

Also it never stays at STOICH. when im just cruising and stay at a set RPM at whatever MPH it will read about 11-12.4.
The WOT readings are from when the ECU goes into open loop, when it is not using the o2 sensor to make adjustments, and yours look about the same as mine (9.x - 10.x).

Maybe also drilling out the J-tube, with no AFPR, is dropping the pressure, or causing it to fluctuate? Don't know, just a thought. I think I would try an o2 sensor first - maybe even connect your wideband in place of the stocker, if it has a narrow band output (that's how I've got mine now, using the LC-1). To my knowledge, the NA o2 sensor won't work with the turbos, because it doesn't have the heater (only one wire, not three).

Hope that helps :sad:
 

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That's the same problem I had with a Lex and 550's. Way to rich. I went back to the Lex,440's and aic I originaly had until I got an safr. You shouldn't have a problem with closed loop. I don't know why your safc can't pull enough fuel under open loop though. You sure your safc is hooked up right?
 

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My guess would be you wired up the AFC wrong. At idle you should be able to remove enough fuel to make it stall. Make sure the AFC->AFM wiring is correct. Second, lose the stock FPR and get a Aeromotive 1:1 unit. This will bypass all the J-tube crap mod from 1994. The 1:1 means it raises the FP 1psi for every 1psi of boost. Set the base pressure to 43.5psi which is what RC recomends for the 550s (if you have RCs). Upgrade your FP to a Walbro and go tuning. The dyno Jet would be best.
 

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Discussion Starter · #7 ·
it has something to do with the lexus afm. when i just driving it sputters and when i punch it it just goes rich. I thought during just cruising its suppose to stay at like 14.7 but it stays at like 10.8-12. and doesnt ever go close to 14.7 unless its sputtering and bounces to lean.

What does anyone think it is. it has something to do with the AFM cuz it never does it with the stock one.
and it was doing that so i did the j-tube thing and the 12volt thing and it didnt change anything. so i put the 12v thing back to normal.

it did it before i had the safc (OLD knob version) (can adjust it +-30) and im pretty positive its hooked up right.
 

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Discussion Starter · #9 ·
im using the lexus sensor.
ok, a long time ago my stock afm sensor got wet and took a crap.
i bought a full Lexus AFM with sensor for 130 and got it the next day overnight shipping.
well i didnt have 550's then and just took the sensor off and put it on the stock afm. Ran Perfect...
 

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The J-tube mod LOWERS the fuel pressure which is why the car spudders at idle. The J-tube mod is for those who run the stock FPR w/ no AFC or tuning capacity.

The 550s need to be run a 43.5psi while stock is 32? And drilling out the J-tube lowers the FP even lower than 32! And the reason the car runs better with the stock AFM is because the FP is too low. The stock AFM sees more air and therefore, the ECU adds more fuel. The Lex sees less air so it leans out even more. IF your using the same electronics box for both then the Lex connot be bad. And the 10.8 A/F can be removed with the AFC, if it's hooked up correctly.

And as for the AFC, you should be able to STALL the car(by removing fuel) at idle or any low map RPM if you wireded it up correctly! It's a self test.
 

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Discussion Starter · #11 ·
it doesnt sputter at idle. it sputters while driving. on the knobs on the safc i turned the knobs down all the way to -30 and it didnt stall. at idle my car sits at about 10.5 and when i leaned it out it just went to about 11.

and my car still sputtered Before i did the jtube thing and it still acts the same with the jtube drilled out. and it still acts the same with the 12v mod that makes the fp go to 36 or 40psi at idle cant remember.

But why does it run fine when i unplug the O2 sensor?
 

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arent you suppose to be using the stock afm electronics with the lex afm housing??? That is how I used mine. 43.5psi on the 550's is too high, period. Set the fpr to stock settings and then lower the pressure to obtain the a/f you want. Lex afm and 550's cause a rich cond. as you know and that is why you SUBTRACT fuel. so raising the fuel pressure causes you to run even more rich. I just dont want you to get the wrong advise.
 

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I don't think the Lexus Sensor will run well with the car. They are two different part numbers and made for different ecus. It may run crappy ..but not well.
I would change it for a stock 7m sensor and I am sure that most of the problems will fix itself.
I have a Lexus sensor and am not able to run my car with it either.
When I did mod my last &M with the Lexus AFM housing, I did a bit of research and most of them pointed to using the 7m sensor and not the Lexus one.

That is why my question related to the type of sensor u were using.
 

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Your biggest problem is one, using the stock FPR and second, not knowing if the AFC is wired up right. Sounds like it's not. Hell, AFCIIs are only ~$300. Go get one. Do what others have done time and time again (lose stock FPR). Ultimately, the answers to these problems rest in your own hands.

BTW the stock Lex electronics box works fine.
 

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I never had a problem using the stock FPR, just my 2 cents
 

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Discussion Starter · #16 ·
what are the other options to get rid of the AFM thing? VPC? what would you need with that? i dont know everything with the chip and stuff? and the maft would cost like $500.
 

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Discussion Starter · #19 ·
well, right now i dont have much money so i buy things here and there.
the SAFC i got for free. and i had the instruction manual and the diagrams and stuff. so im pretty sure its set up right. but even with it OUT of the car it still acts the same. i mean, i can see on the wideband where it leans it out a LOT and it sputters a shit load and then i richen it up and it runs better.

but the lexus sensor works with the stock AFM.

what is everyones thought on the O2 sensor?
 

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I still think you should try the o2 sensor first - it may not be the problem, but it's easy to do, and will remove one possibility if nothing else. If you've got the NA sensor you mentioned before, you could use that for testing, but since it doesn't have the heater circuit you probably shouldn't use it on a regular basis, and you would need to allow more time for it to come up to temperature. Or just hook up your wideband's narrowband output (if it has one) in place of the stocker.

Given the readings you're getting, it seems the ECU is over compensating for the Lex AFM - dumping in more fuel than it should. As for the AFM electronics - apparently, some of the Lexus units have different boxes than the stock MK3, some are the same. Compare the p/n with that of your original; if they're the same, then that's another thing you don't have to worry about ;)
 
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