Crazy afr, maf? injector? Fuel pulsations?
 

Update: issue has been resolved. Went to a friend who had a external wideband. My issue was incorrect readings from my wideband.

So here we go...
Ive been dealing(for 6 months) with issues regarding injector tuning. I had my car perfect on fic 1150cc injectors, then i bought the new fic 1120's. At this time i also rebuilt my turbo to a hybrid 20g, and upgraded my intercooler. I have a built 2.0l with all the goodies in the head w/ 280 cams. Im running a stock fuel rail and reg/solenoid. Walbro 450 pump w/ stock wiring. Stock int mani and tb with omni map. Stock maf, mishimoto catch w/ stock pcv still installed. Boost/vac leaks checks. Exhaust leak checks. All passed. Egr delete and evap delete. Brand new alternator, cam sensor, tps, radiator, vac lines and other oem non performance parts. (Car has not jumped timing and ill be doing a compression check later today). Was running cop kit but now im back to stock coil pack to diag these issues.

Now onto the issues. (2 issues)

My main issue thats bothering me is my afr. I can tune it perfect to almost 0% ltft. I can start it up and get average 14.6.
But after a while(it can be 10 minutes of driving or 2 hrs) it will randomly act up... My afr starts going bananas. Starts maintaining 13.8 then fluctuating to 18.4 or higher then to below 10.0. Then back to 13.8. Ive tried everything in my knowledge to tune this correctly. I got so frustrated, i went and bought id 1050cc high z injectors(i was blaming my fic's). I tuned them and then bam. Started happening again. Ive also removed most upgrades and put stock parts on and same thing. Running on 93 oct. Ive tried maf scaling, which makes it worst. Also ran tephra v7 and no change.

Second issue, im getting a shutter so to say at high boost 28psi and above around 5400rpm or 6400rpm. As well in very light throttle cruise. Ive logged and these issues have occurred with no knock and with good afr (11.5).

So, is it my tuning? Or is it a physical issue with my vehicle?
Can it be fuel pulsations in the rail? But im only running 1050cc
So why would i have that?

I can log and upload or email log if some one would like to look at it.

Thank you in advance for the help, info, and knowledge.

Great to have you post up in one of the Tech threads

Dont have any real tuning knowledge other than if you were to post one of your logs, that would help

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My .02 {thumbup}

I've uploaded three logs. I believe i've changed the injector scaling and latency since last log(not sure due to all the logging and tune modifications). If any more info or a updated log is needed, just let me know.

You may need a new wideband 02 sensor.

possibly, I need to do a resistance checks and compare that to specs.


I was messing around with the isc values and they seemed to have a huge impact on the afr issue at idle. (obviously)


Here are my values, any thoughts?


also engine drops to 500 rpm when A/c is on

Another one with a 450 pump and stock reg?

No idea about what the fuel pressure is doing ?


You might be seeing 60 or 70 PSI on the gauge at idle.


Lets say it's got 60 PSI on the gauge at idle.
Then the pressure across the injector will be close to 70 PSI.
Your new FIC 1120s will think that they're 1420s.
But only at low load.
Your 1150s will think that they're 1470s.
Your 1050s will think that they're 1340s but as soon as the voltage drops with switching on lights, fans demister etc, the pump pressure will drop to close to what it should be. The flow rate will follow.

So what you are saying is, that the stock fuel reg is not maintianing correct rail pressure. And im over fueling until the alternator steps down and supplies less volts to the pump.

So the only way to correct this issue is a aftermarket regulator?

Some of the engine / tuning guys have recently been debating this issue back & forth and their are opinions for sure!

Make sure you get this symptom fully sorted out before upgrading the FPR

Found some irregularities in my open loop tables and corrected them.

Rightsaid fred you are correct. Once theres high electrical load, thats when the afr starts dancing. I am running a mini battery but log data is saying that battery voltage stays the same.

Should i get a amp clamp and check amperage to the pump or should i test fuel rail pressure? And what is the best way to correct this? A new regulator?

If the pump is on stock wiring with the high/low circuit it more then likely isn't seeing more then 12-13 volts when on the high circuit and 9-10 on the low circuit.

Test the voltage going to the pump at idle and when under boost . IIRC the stock high/low crossover is 1-2 psi.

If the pump gets rewired it will need a proper high/low ( MRFRED ) circuit or an aftermarket FPR to bring pressure down.

It could also be a few other things but getting the voltage is a piece of the puzzle. You also want to check all the grounds on the car and make sure it has the one near the battery and intake intact.

With a stock pump you'll see 13 ish volts at the pump at low load if you bypass the pump resistor.
You'll see about 9 volts at the pump with the resistor in circuit.

But only with a stock pump.

All aftermarket pumps draw more current (they're more powerful) so even though they flow more with the resistor in circuit, the voltage will be a bit less.

A 455 pump is taking it to the extreme.
One way to lower the flow at low load (resistor in circuit) is to increase the value of the resistor slightly.
It doesn't really work because then when the fuel requirement suddenly rises (WOT), there's insufficient voltage to the pump and the pump will stall and you'll have zero fuel. Maybe OK with a 255 if you test it properly with the right resistor.


There's more than one way to fix it.
A good quality FPR with lots of flow is one way (maybe an Aeromotive?).
Using multiple stock FPRs in parallel is the best way in the long run due to the extremely high quality of OEM parts compared to aftermarket junk.
A lot of new cars these days use PWM control of the pump so you only supply what you need.
Otherwise 2 or more pumps switching in stages.


The mini battery doesn't help either. The battery capacity helps in soaking up the sags in voltage.

Try running a single 255 and see if the issue persists. That should provide enough fuel for a 20g on 93. The 255's will not over run a stock fpr like the 450's do.

High electrical load? Measuring current or voltage where? Check you motor ground and grounding points. I would also run a 10ga. wire to the pump. Wires are undersized for a 255 much less a 450. Resistor will be getting hotter with the bigger pump, when things heat up they do crazy stuff like this. check the plug connector for burnt pins discoloration of the wires.
Lastly I had an issue with my FPR solenoid leaking causing similar issues, but that was under high boost. I would just remove it as it is a liability and not needed anyway.

I would probably just replace the resistor as well, they get corroded at the crimp and sometimes eventually burn off.

You need to log fuel pressure

What ROM are you running? If you can turn off closed loop and see if the problem persists.

Drill the siphon to 9/64 if you haven't already. You may be over running the return line (NOT the regulator). On stock wiring with the siphon drilled, the walbro 450 is perfectly tunable in our cars. I would however suggest doing mrfred's hi/lo voltage rewire to get the most from the pump when you are in boost running it on hi voltage.