S4 NA
Street ported
Full exhaust
Intake
Rtek 2.0

I have an S4 NA that will randomly lean out from ~15 AFR to ~19-20 AFR while cruising. When thes happens if I give it more or less gas it will richen back up to normal. This happens at freeway speeds mostly

Also I have had to use my RTEK 2.0 to lean the car out to ~13:1 in open loop. Without the RTEK the car would run ~18-19:1 under load. I have my RTEK maxed at +50% fuel just to get the tune in the ball park (high 13/low 14 AFR at WOT), but it still could use a bit more fuel under load.

I have replaced the following -

Fuel pump
Fuel filter
Checked fuel pressure (per FSM and on the road) I see 40 PSI under WOT conditions.
RTEK reports the secondary injectors are firing, but I have not checked per the FSM.
Car appears to have the correct injectors in the secondaries. I have not checked the primaries.

I dont think this is a fuel supply issue. Any ideas?

 

Does the engine start bucking when it goes really lean? Do you have an airpump installed?

 

Yes it does buck, or you can feel it lose power. You can see the change in EGT and AFR as well. At WOT, it runs fine. I just had to add +50% fuel adjustment to get the AFRs in the ball park. The car picked up a lot of power when I did this.

Yes the airpump is installed, but it is doing nothing. The car has no cats, and the cat air pipe is currently plugged. The wideband bung is near the engine. The car had the same behavior with a main cat and cat air pipe installed.

Question - Does the air pump only deliver air to the cat or somewhere else as well?

Also, the aux port actuators are wired open. Secondary injectors are set to come on at 3000 RPM.

 

If you have the air pump and ACV still installed, this is normal. Air is dumped into the exhaust at cruise and idle.

 

It is not dumping anywhere in the exhaust. I have a aftermarket header and no cats. The air tube that would go to the cat is plugged.

My wideband bung is upstream in the header anyway.

 

how is your airflow meter mounted?

 

Stock from what I can tell. The car does have a K&N FIPK (just a cone filter adapter) but it has all the stock intake piping from the throttle body to the AFM.

Would testing the AFM per the FSM be a good next step? That is where I am leaning at this point.

I did replace the CAS last summer (a pickup broke), and there was no change in this behavior after I did that.

 

Primarys are too small.

Or the AFM has been buggered with. Look at the large black plastic cover over the electrical internals of the afm and determine if someone has had that cover off ....or not.

Or the RTEK is set for 550's instead of the 460's that should be in a stock n/a.

 

The mounted position of the AFM is also important, as arghx noted.

 

And for now set the ATP setting to zero altitude.

 

ATP is set to zero. RTEK is set for 4x460 injectors. I'll take pictures of the AFM cover tomorrow.

The secondaries are the correct injectors. I verified that by the model number.

I'm not sure that it is incorrect primaries, but I have not checked for certain. The car only does this while crusing, and other times it is fine.

Before the RTEK, the car did the same thing, but was just a lot slower in open loop conditions. It ran fine at idle and low RRM and AFRs were in the 14-15 range but would lean out randomly as it does now. In Open loop the car was very lean, around 18 AFR.

Hailers, here is a question for you. What kind of injector duty cycle numbers do you see in your NA car?

 

bump!

 

I'm not sure it'd be relevant. I run straight E-85 with 550's as primary injectors and the fuel map sort of jacked around plus having it still set for 460's on the RTEK. That's on a 86 non turbo.

Got two turbo's on E-85 with 720's in primary and secondary and the RTEK set for 550's.

Butttt..........I might look tomorrow when it's in closed loop cruising on the way to the bike path. The 86 non turbo that is.

 

Thanks.

As a band-aid to get more fuel in open loop I bought 2 550 cc injectors to use as secondaries. This should give me a bit more headroom to get the AFRs a bit lower. I have new 460s as well and I am thinking I might replace the primaries while I am in there.

 

UPDATE -
I just tested my AFM, per the testing outlined in the FSM and everything seems ok except for the Intake Air Temp sensor. I get no resistance reading at all when performing that test. My AFM looks to be completely factory sealed and not tampered with. The flapper works fine.

When performing the E1 to Fc terminal test with the flap open the resistance I got was 001. The FSM states this should be 0. Could this or my lack of IAT be causing my problem?

Tests were performed per page 4a-60 in the FSM
http://www.teamfc3s.org/main/factory...SYSTEMS_NA.pdf


I am trying to get a good used AFM from another member.

 

do you still have the stock narrow band o2 sensor hooked up? have you checked that?

also, have you checked the other fuel filter/strainer in the fuel tank?

you might want to try and get your fuel injectors cleaned and see what that does.

 

It was not hooked up when I bought the car. I bought a new one and hooked it directly to the ECU (bypassed wiring harness) it did the same thing.

Now I have a wideband in the car and am running a simulated narrowband signal from that to the ECU. Still the same thing.

 

Hey, I'm seeing the same problems. I'll check my afm tonight. I have a RTEK too, but turbo. Hmm... I am running the stock o2 sensor. Do you have any - (negative) fuel correction in vacuum? You said you had to go to +50%? But rtek is only 37%? or whatever? you mean 50% of the allowed positive correction(1/2 of 37)?
Cruise vac is about what 10-20in/hg?

Hmmm.... Good luck. If you look in the RTEK AFR Tuning thread, I have posted logs showing when I'm seeing this lean condition. It seems when your cruising and then just a little more throttle to maintain speed it goes lean.... 17-18 AFR's.

 

The S4 NA RTEK 2.0 allows +/- 50% fuel correction. It has been awhile since I have logged the car, but that cruise vac seems about right. I will log it again and see if I have similar findings to yours. I am putting turbo injectors in for my secondaries as a band aid for the open loop condition.

Sometimes mine will just lean out without moving the pedal while cruising on flat ground. I don't know if this problem is related to the fuel problem I am having in open loop, or if they are seperate issues.

 

why do you still have the air pump and ****? Gut it, and if you can tune the RTEK, gut the stupid aux port sleeves. At high rpm, they provide a bigger restriction to the intake than they give benefit. Trust me, I've done it with my car. Totally gutted emissions, removed sleeves, welded open the VDI thing, and ran the car with an RTEK 2.0

The 6 port intake is a dumbass idea, and after you tune the map properly, you dont need it.

 

utter foolishness

 

orly?

Tell that to Chris Ludwig, who gave me that advice in the first place.

 

Mine checked out. Well at least the thermistor had the correct resistance. Good luck though...

FWIW, I'm running 550x550 setting with 680x1000 injectors.

 

air pump dumps into the exhaust ports ahead of the o2 sensor... although the ACV should be venting over 2500rpm

 

IF you have the airpum and ACV functional, then try this. Remove the BLUE electrical plug from the Relief solenoid. That act will cause the ACV to dump all the airpump air into the silencer in the right front fender instead of the exhaust ports.

Now go for a ride like that and compare it with the results you were getting before. If it still goes lean then it's not the airpump air going thru the ACV. Simple as that. Like mentioned above, it's probably the airpum air causing the *lean problem* when the blue connector is on the relief solenoid.

If so, then it's not really a lean mixture problem at all in any way.

IF you have a RTEK 2.0, you can look at the page that shows the switching...relief solenoids conditoin. I'm fairly sure if you drive along at a steady speed, the RELIEF will not show to be energized, but the moment you let off the throttle a bit it will get energized (meaning acv air will go to the exhaust ports and now mix with exhaust gas and cause the 02 sensor to show...lean). I'm fairly sure about that. Plus maybe the Port air solenod going open also. One or the other. Hedge, hedge, hedge, hedge.