Lexus AFM Clarifications Please

[gottadiesel]

To begin with I am going to list mods so that is an understanding of how I got to where I am:

1988 5spd 7mgte
Motor & tranny top to bottom complete re-build - Stock internals
Greddy 2.0mm MHG
ARP Head, Main & Rod Bolts
Upgraded oil pump (BP'd for higher flow)
Arizona Performance HF Oil pump hardpipe.
DM 57 Trim bolt-on upgrade
Synapse Engineering BOV recirculated with custom 1.5" nipple on intake
Alum 2.5" hardpipe & intercooler
AEM TruBoost
Apexi Neo
AEM Wide Band
Lexus AFM
Siemens 550cc injectors
AFPR
Denso MarkIV TT FP
Stage 3 Action clutch
Full 3" exhaust

My primary issue - it is running lean through out (at least to 45% throttle, as high as I have taken it so far) without compensating with the NEO, which I know I do not want to do until I hit 70% or WOT.

My FP is at 34psi with vacuum, but I have tried to reset the EFI take the Neo out of the picture and my AFRs as idle are off the meter, so greater than 18... if I up the FP to about 40, it will come down to about 17.8 or so... still real lean and stumbles to idle and run.

So I think one of my mistakes early on was to sell my stock AFM, as articles that I am now reading on the upgrade all seem to point using the stock Karman Sensor, yet the lexus one does not throw a code?

Can someone confirm that the ECU will not respond correctly with the lexus electronics instead of the stock ones?

Also I know there is a custom adjustment bolt manufactured for the purpose of having more adjustment on the un-metered air, is this a requirement or a nicety to fine tune the AFR? My understanding though is that the more open the un-metered air is, the higher the fuel cut, so I am thinking wider open is better to a point of course...

I also have a new Denso O2 sensor, IIRC there is no difference in the two blue wires, they are both heat signals correct? I am just thinking that if my feedback from the O2 is incorrect that also would create an issue. What I have not done, mainly due to the fact that I have to make a couple of other changes after running it a few miles... so can't start ATM, but want to check my Vf voltage and see where the ECU is at with compensation from baseline.

So I think I have found a set of stock electronics from someone on this site, but I am not convinced yet that, that is my issue.

Any thoughts would be greatly appreciated.

 

[radiod]

I can't help you with too much, but I can tell you that the stock electronics are the same as the lexus electronics, just a different housing. The adjustment screw shouldn't be necessary in getting a global AFR change if you've got an adjustable fuel pressure regulator. I don't know why it's that lean when you're giving it 40psi of fuel...hopefully someone else can chime in about the AFRs.

 

[Nick M]

Can someone confirm that the ECU will not respond correctly with the lexus electronics instead of the stock ones?

It will respond correctly. You should use a known good unit.

Also I know there is a custom adjustment bolt manufactured for the purpose of having more adjustment on the un-metered air, is this a requirement or a nicety to fine tune the AFR? My understanding though is that the more open the un-metered air is, the higher the fuel cut, so I am thinking wider open is better to a point of course...

The further out the screw is, the leaner you will be, in addition to the raising of fuel cut. The meter is reading less air.

 

[gottadiesel]

NickM - Thank you for the clarification - I will double check resistance on pins of the lexus afm, i did test once before, it also does not throw a code... in reading the article from someone documenting this upgrade, I thought the sequence was, unmetered air would cause O2 sensor to say I am lean, which would cause ECU to add fuel, then you use 550cc as when it calls x amount of fuel it is really sending y amount which is greater, so would even out the being lean...

So I guess one question still is - can you calibrate the bypass airway with the factory screw or do you have to but the custom one that I know some are using?

Any other ideas as to why I would run lean then, assuming the AFM is good?

Again I just got done getting DP ready to put back in, so hopefully soon I can test the Vf voltage and post what it is doing.

Thanks!

 

[Nick M]

To elaborate, when the screw is open and unmetered air is entering the engine, it causes a lean condition. The injection pulse width, that is how long the injector is turned on, is lower because the ECU thinks less air is entering than really is. The best way to run the Lex meter is with the screw all the way in. In terms of proper air fuel ratio.

Get out your multimeter, and put it between pins VF1 and E1. I think. Look in the repair manual. If the ECU can not richen anymore, it will say so.

I have no comment on the Neo settings, as I haven't used it. If you use it to raise fuel cut, that also makes you leaner during normal driving.

 

[gottadiesel]

To elaborate, when the screw is open and unmetered air is entering the engine, it causes a lean condition. The injection pulse width, that is how long the injector is turned on, is lower because the ECU thinks less air is entering than really is. The best way to run the Lex meter is with the screw all the way in. In terms of proper air fuel ratio.

Ok, I will pull AFM and see where how far it is in right now, I think it came off a lexus before I got it, so I assume it was where the lexus ran at stock.

Get out your multimeter, and put it between pins VF1 and E1. I think. Look in the repair manual. If the ECU can not richen anymore, it will say so.

Yeah that was my next step, you are right it is Vf1 and E1, it ranges from 0vdc to 5dvc app, about 2.2vdc should be base-line, more it is add fuel, less it is taking it away... so yeah if it is at 5, then it is maxed out.

I have no comment on the Neo settings, as I haven't used it. If you use it to raise fuel cut, that also makes you leaner during normal driving.

Not using it to raise fuel cut, just add more air to the Karman signal so that the ecu will add more fuel... so if anything as I go up, fuel cut will get lower... anyway here nor there, at this time i have taken it out of the picture as it should not be needed for idle to 69% throttle...

Thanks for your time, I will post when I have the Vf readings

 

[MA70_Powa]

I think you have a similar situation to me. I did the lex afm/550s upgrade and it's super lean up to ~3000rpm.
I tried my orginal AFM karman sensor and the one on the lex afm but both gave the same result.
I just added more fuel using my SAFC (around 20% more at idle...) and all is well

Oh, and it went from super lean down low to quite rich up top for me, so I've also taken out a chunk of fuel in the higher rev ranges (is still rich tho)

 

[gottadiesel]

I think you have a similar situation to me. I did the lex afm/550s upgrade and it's super lean up to ~3000rpm.
I tried my orginal AFM karman sensor and the one on the lex afm but both gave the same result.
I just added more fuel using my SAFC (around 20% more at idle...) and all is well

Oh, and it went from super lean down low to quite rich up top for me, so I've also taken out a chunk of fuel in the higher rev ranges (is still rich tho)

Well I do have 122 miles on it so far and that is what I did in order to compensate, but I guess my concerns is that it seems to be a common theme throughout numerous threads that I have read, that it is best to lest the TCCS do its job up to 69% throttle, so that has me concerned that something else is wrong causing this issue.

Also an issue, but I was leaving it alone until I resolved this issue 1st, as was not sure if one was causing this other, but when I hit about 4psi and 4k rpms I get a stutter, now I am not sure what it feels like to hit fuel cut, is it quick or does it pause for a second or two? I see the AFR go off the chart for just like 1/2 second then comes back, but I also naturally left off the throttle so that may be why it recovers. If that is the case then I have an issue with adding any more fuel with the NEO... but like I said I want to get this idle and low throttle setting issue resolved 1st...

Thanks for the feedback though, how long have you been running with your SAFC controlling full band of throttle? Just curious.

Thanks

 

[MA70_Powa]

Fuel cut feels like you'd be driving along and you decided to smash the brake pedal to the floor for about half a second. Your engine pretty much dies for a second or two, and then you can keep driving.
I had it a few times before I did the upgrade...

I've been running it with my SAFC for almost a year now. It's been great except for once when it decided to wipe itself and I had to get it re-tuned... (So I've written down the settings on paper now as a backup )

I should say also that I'm running the stock FPR - I have the Aeromotive kit sitting in a box because I don't really need to install it!

 

[gottadiesel]

So a quick update, I have added a restriction screw now to the un-metered air port in the lexus afm body, all the way in should be blocking 80% or so, reset efi, neo is completely disconnected (has to be sent back to factory for firmware anyway, so thought that was my issue). It still ran really lean though.

The Vf varied between 0 and 5vdc, if I would rev it up a little past idle it would often jump up to 5vdc. but also sounds like it is missing when I try to hold it at 2-3krpms. when it misses though the AFR jumps real lean.

One change I made since it had been running better when during my 1st 5 heat cycles, is I added the recirc on the BOV, it is a synapse (I know has been widely debated) but thought I was good as long as I was recirculating it. So anyway I pulled the recirc tube off and plugged it... and I will be damned if it started running rich.. how could recirc cause umetered air to come in?

So it is better, but I can't leave it that way, but still not consistent, the Vf most of the time will run now at either 1.2vdc or 2.2, sometimes 3.5... so better than 5, but still hesitated horribly when I try to drive it... once again goes real lean when it hesitates...

Does that sound like an injector not working right? As if it was a plug not firing it should go real rich not lean, but no injection should = no fuel which should = lean? Am I thinking straight...

any additional advise would be appreciated.

 

[CajunKenny]

Any codes yet?

While it's idling, move/bend/flex the CPS wires and see if anything changes.

Also, if you have a 12v tester, attach it to the negative battery terminal and poke around (not poking thru ) your plug wires and/or coil pack.

 

[gottadiesel]

Any codes yet?

While it's idling, move/bend/flex the CPS wires and see if anything changes.

Also, if you have a 12v tester, attach it to the negative battery terminal and poke around (not poking thru ) your plug wires and/or coil pack.

Hey Kenny - Nope no codes.

Have double checked CPS connections and timing all good, I replaced CPS wires back about 12" to eliminate cracks etc...

Yeah I have a Fluke 87 meter, what am I looking for? voltage leaks? Would be greater than 12vdc though... Was I making sense though, I know it sounds like it could be a miss in ignition, but would not the AFRs go rich and not lean if it was spark related? Just asking, I was going to try and change back to my stock plug wires also, but was trying to eliminate other obvious issues 1st... like why the BOV being recirculated would cause it to run lean? doesn't make any sense to me?

Also I keep going back to wondering why the last owner installed a jumper that by-passed one of the resistor packs on 2 of the injectors, I guess I should check resistance through the resistor pack and make sure they are all correct...

Any other thoughts?

Thanks

 

[jetjock]

Not sure what Kenny is getting at with that but the Fluke 87 is too nice a meter to blow up

I know it sounds like it could be a miss in ignition, but would not the AFRs go rich and not lean if it was spark related?

Not that I think it's your problem but misfire will result in a lean indication on a device that can only measure O2...

 

[CajunKenny]

^Agreed. That's actually the very meter I have! There's no way I'd want to blow mine up!

I was referring to the standard automotive 12v tester that has a lamp in the handle. My thought was to see if the coil pack might have a crack in the epoxy, or whatever that stuff is. And also to check to see if a plug wire was faulty (although I know they're new).

Just don't scrap the car! Not yet anyway... :biglaugh:

 

[gottadiesel]

Not that I think it's your problem but misfire will result in a lean indication on a device that can only measure O2...

OK, so I guess the unburned mixture of gas and air are not able to be read by the O2 sensor? So do you have an idea outside of misfire or are you just saying you are not sure but don't think it is a misfire? hope my question makes sense :icon_bigg

^Agreed. That's actually the very meter I have! There's no way I'd want to blow mine up!

I was referring to the standard automotive 12v tester that has a lamp in the handle. My thought was to see if the coil pack might have a crack in the epoxy, or whatever that stuff is. And also to check to see if a plug wire was faulty (although I know they're new).

Just don't scrap the car! Not yet anyway... :biglaugh:

Yeah gotcha lol, I have been using to measure other signals for accuracy, but yeah would be leery about getting close to anything above 600volts with it... yeah I can dig up one, if not easy to make one with a marker light...

Oh and by the way, no my wires were not new, I tried to buy new MSD 8,5mm set, but they stopped making them, so I found a used set that (I was told) only had 3k miles, but I can put my old NGKs back in, they only had 5k or so on them...

Yeah the scrapping comment I texted you last night... that was just the frustration talkin... :icon_mad:

Thanks - I will post later today what I find... gotta get back to the work that makes money for awhile 1st...

 

[3p141592654]

If the cylinder misfires, the 20% oxygen in the charge does not get converted and flows right into the exhaust stream. The O2 sensor senses the high level of O2 in the exhaust and interprets that as a lean mixture. What you want is an exhaust gas analyzer. That will tell you what is going on but I would assume you don't have one handy.

I would start by figuring out why the injector resistor pack was shunted. That is not a good thing to do unless that bank is using high-impedance injectors for some reason. Having different types of injectors in the same rail is not going to be a good thing either.

 

[gottadiesel]

If the cylinder misfires, the 20% oxygen in the charge does not get converted and flows right into the exhaust stream. The O2 sensor senses the high level of O2 in the exhaust and interprets that as a lean mixture. What you want is an exhaust gas analyzer. That will tell you what is going on but I would assume you don't have one handy.

I would start by figuring out why the injector resistor pack was shunted. That is not a good thing to do unless that bank is using high-impedance injectors for some reason. Having different types of injectors in the same rail is not going to be a good thing either.

Thanks for the explanation and nope sure don't have an analyzer handy...

Well since that was shunted, it was found during my tear-down, I have had a total re-build, which included new 550cc injectors, so I took out the shunt when cleaning up harness. I have double checked resistance of injectors (all right about 2.2 ohms) and the stock resistor pack (all are 3.2 ohms) so all looks good there... I got rid of the other injectors, so I still have no idea why it was done... it ran fine before I pulled it down for rebuild...

 

[Nick M]

Not sure what Kenny is getting at with that but the Fluke 87 is too nice a meter to blow up



Not that I think it's your problem but misfire will result in a lean indication on a device that can only measure O2...

To continue, on a gas analyzer, an ignition misfire will result in high HC and high O2 content, with low CO2 and CO will be where ever your settings are on the car.

And to continue 3p's comment, a gas analyzer is found at the dealer or a shop that is fully competent to do things like emission trace anaylysis. Some dealers are so ma and pap small they don't have it either.

 

[gottadiesel]

Thanks Nick, yeah that makes sense. I changed back to my known good stock ignition wires, new plugs gapped to .26, I also double checked all intercooler connections, after being heated up a few times, seemed like a get get a couple of turns from each one... also create a little more restriction in the bypass airway of the AFM, re-connected the recirc from my BOV, reset EFI...

Runs much better then yesterday at idle, but when I try to drive it, still is missing/hesitating... whether that is a mis-fire or an injector fouling not sure... I am about ready to go ahead and pull all the injectors and take to someone to have flow tested...

 

[gottadiesel]

After re-testing coil, ingnitor, ignition wires, resistor pack, resistance of injectors and on and on... I have pulled the plenum and now have pulled the injectors. I am going go do what I should have 4 months ago when they came in, get them flow tested by a fuel injection shop...

One point of interest though, is that I installed 6 new plugs in today and it ran at idle, with some revving etc while testing for 20 minutes or so and went maybe 2 miles, plug #1 is black, all the rest are clean... but for such a short time, i am having a hard time telling whether it is stubborn rings that have not yet set in or if it is from being overly rich... There is a trace amount of liquid on top of the piston, perhaps I can use a Q-tip to get a sample...

Any thoughts on the process to date would be much appreciated. Thanks