Lex/550 problems. Extremely lean

[crimson88]

So this weekend I installed Aeromotive afpr, 550s, and the lex afm. Also installed Walbro week before, and it's been running fine.
Here's the issue, started it up and won't idle for shit, off the uego gauge lean. Messed with it for awhile and couldn't get it to run any better. I put the stock afm back on, and it runs fine, just richer than before(idles around 13.5) . Just a few minutes ago I tried swapping the afm again after the car had been running fine with the stock one. Same thing, extremely lean (18+) to the point it will hardly idle. Blipping the throttle drops it momentarily to 17 ish .

Any reason it's going so lean? I read if anything it should be rich correct? I'm using the same electronics on the afm, just swapping it between the stock and lex. Base fuel pressure is at 40

 

[IndigoMKII]

has the air bypass screw been messed with?

 

[jetjock]

...I put the stock afm back on, and it runs fine, just richer than before (idles around 13.5) ...

So you're modding the engine even though it doesn't work correctly when stock?

 

[crimson88]

It did run correctly stock. Now, with the 550s and the stock afm it runs OK, just richer. Which I'd expect with bigger injectors. But once I put the lex afm on, it goes extremely lean and is hardly driveable.

I haven't Messed with the screw any yet, couldn't get the damn plug out to get to it. Will drill it out tonite so I can try messing with it

 

[Suprapowaz!(2)]

You could always bump up your fuel pressure until it's happy at idle & cruise. I would tap into the diagnositic block E1 + Vf1 and monitor your stock ECU making corrections.
Just be careful when testing WOT that's you're not going lean. Which turbo are you running, and how much boost do you have it set for. I would run the lowest boost while adjusting the fuel pressure.

 

[Nick M]

The Lexus (UZ engine)housing will not cause a rich or lean condition with 550 injectors. You need to find what you did, or what was wrong before hand.

 

[crimson88]

I have a billet 57 trim. Usually running around 11 lbs. Likes I said, changing nothing but the afm is causing this lean condition. I swapped back and forth a couple times now. Stock afm, drives good, boosts fine, idles nice. Five minutes later with the Lex afm, won't idle, off the chart lean, lean under part throttle, but richens up when I get on it.
At first I left the lex on and drove for about half an hour hoping the ecu would learn to idle. I disconnected the battery to reset it. It never got any better tho.

I pulled the iscv and cleaned it, and it helped a little.
I also noticed my fuel pulsation dampener is seeping/leaking slightly. I just ordered the bypass hose from Driftmotion.

 

[Supracentral]

Are you using the electronics from the stock AFM on the Lexus one? If not, move them over and see what happens.

 

[crimson88]

Yes, the electronics on the lex were damaged when I got it. So I'm swapping my stock electronics back and forth when I swap housing. I even accidentally left the afm unplugged at one point yesterday with the Lex on, and it idled fine. Then I realized it, plugged the afm in, and it immediately went to shit.

 

[Nick M]

Why does this smell like it has K&N oil written all over it?

 

[crimson88]

Apexi intake. I'll list every mod.

Apexi intake
Billet 57 trim
Hks ssqv
Spearco ic
Bic ddp
Test pipe with cutout
3 inch exhaust
Aem tru boost
Aem uego
Rx7 550cc injectors
Aeromotive afpr (currently set at 42 lbs at idle with vacuum disconnected)
Walbro 255

I don't think the sensor is bad, like I mentioned it runs great when it's on the stock afm housing

 

[Moy]

Out of curiosity, did you change your fuel filter when you installed all of your other fuel system upgrades? If not, a partially restricted filter could cause lean conditions at idle due to low flow, but at higher pressures the flow might improve.

Also, how did you install the Walbro? Did you do the 12v mod? How's the wiring? How's the pump inlet filter? Have you done volume testing on the fuel pump to make sure it's flowing the manufacturer specified amount?

Are your injectors clean? Are they sticking closed?

Aside from swapping AFM housings, what diagnostic procedures have you followed?

 

[Nick M]

like I mentioned it runs great when it's on the stock afm housing

You saying it over and over does not make it so. The housing size is correct for the injectors. There is something else wrong. Nobody can see the car but you. Is the accordion pipe hooked up? Is it cracked?

 

[Amtrack]

Rx7 550cc injectors

High or Low Imp?
There are two types of RX7 injectors as far as I remember.

There is something else wrong. Nobody can see the car but you. Is the accordion pipe hooked up? Is it cracked?

I am thinking of other pipes like the one directly after the turbo or the one that connects 3000 pipe with the throttle body (as both of them are very common in failing and cracking).
With stock AFM and 550s it should be pig rich (around 25% too much fuel throughout the whole rpm range).

But on the other hand it would nevertheless lean out with a cracked intake tubing (after AFM) on idle as it sucks air in through the crack.
Only going to be rich as hell if going into boost as he is loosing compressed air then through the crack.

 

[IndigoMKII]

But on the other hand it would nevertheless lean out with a cracked intake tubing (after AFM) on idle as it sucks air in through the crack.
Only going to be rich as hell if going into boost as he is loosing compressed air then through the crack.

So you're saying a crack in the accordian pipe after the afm will only cause a rich condition because it's drawing in extra air? Um..

 

[Backlash2032]

Pre turbo, post afm air leak.. lean.
Post turbo, post afm air leak, lean out of boost, rich in boost.

Sent from my HTC6435LVW using Tapatalk

 

[Amtrack]

So you're saying a crack in the accordian pipe after the afm will only cause a rich condition because it's drawing in extra air? Um..

Except the accordian pipe.
Every single other pipe (after afm) will cause a lean condition (in idle, as written above), yes.
Under boost you will get a rich condition.

Accordian pipe is somewhat special as there is a vacuum evertime the engine is running.
That´s the reason why our head ventilation goes in there btw.


Oh and something else: if you would have read my previous post carefully, you would have recognized that I meantioned this:

I am thinking of other pipes like the one directly after the turbo or the one that connects 3000 pipe with the throttle body
(as both of them are very common in failing and cracking).

My attention laid on the two mentioned pipes.
But you are right, accordion pipe is special.

 

[jetjock]

...Accordian pipe is somewhat special as there is a vacuum evertime the engine is running...

Not really. If there is on your car you'd better replace the air fliter...

 

[crimson88]

Sorry guys, been extremely busy at work. Updates so far.
Replaced throttle body gasket
Did the 12 volt mod to the fuel pump
Changed the plugs
Tried a different afm sensor.

Car will idle now with different plugs, but still lean. one of the old ones wasn't firing right. I didn't really expect them to be bad, they were installed same time as the 550s so less than 100 miles on them.

Different afm sensor in the lex housing caused no change.

The hoses you guys mention, between the 3000 pipe and to, and coming off the turbo, have been replaced with silicone ones and aren't damaged.

I found a small crack in the accordion hose where it connects to the turbo. I don't think it's leaking, it's not big and I'm pretty sure the clamp still seals it. Ordering a new one just in case.

Have pulled and cleaned the iscv.

Have sprayed everywhere I can think of with carb cleaner to try to find cracked or damaged ic piping, no luck.

At this point it will idle on its own with the Lex afm installed, but still is off the gauge lean

 

[grimreaper]

Care should be taken when considering what fluid and what effective pressures an inj was flow tested at. For example RC 550's flow 550cc at 43.5psi effective pressure. Stock 440cc's run at 36.5psi effective pressure. So at 43.5psi, stock injectors should be flowing 477cc. Never seen a flow sheet for stock inj at 43.5psi. If someone has one, id be interested in a post or pm.

So when the 36.5psi effective pressure is applied to the 550's, your getting 506cc. Which is a 15% increase over stock.

Very important to take into account the density of the test fluid and the overall mass flow rate of the inj. Whie flow is important, we still need the correct mass of fuel to match the mass of air for that 14.7:1 af ratio to occur.

Read http://www.injectordynamics.com/SteckPressureArticle.html
and http://www.injectordynamics.com/NewsletterJan2013.html (scroll to 'Pauls TechnoRant')

Edit: used wrong pressure to calculate %