Lean under minimal throttle
Hello all. I have been having a tuning issue on my mean street 800 system. When it light throttle from 0% throttle i get a bad lean spike, up to 16 to 1 or higher. It happens only under light throttle increase like from 0 to 9 or so tps. If i accelerate harder, it doesnt do it. I have tried messing with accell pump, with no change. It just makes harder acceleration spike more rich. I disabled decel fuel cut and that did not help. I checked my fuel filters and they were clear. I pulled a data log but am not sure exactly what I should be looking for as far as adjusting anything past the basic tuning menu. I am not sure if it is related, but I did have an injector get stuck open recently. The lean spot started before the injector started sticking. The injector issue I also had last year but only twice and did not realize it was a stuck injector. I thought it was a bug in the s9ftware or something.
Anybody have any ideas on what to look for? I am down to either tuning issues, or my fuel pump possibly going bad. I have had this system on for about 1.5 years, and did not have this lean issue until the last few weeks.
Now as an added, I cut the map sensor seal like was mentioned in other threads, and it did not seem to help. Then I tried the factory reset to see if it might be some learned tuning issue, and it got much worse. It was leaning out under normal cruising as well. I am now pretty sure it is a fuel pump issue since the factory reset put the fuel pump pwm back to factory 75 that I had at 100 previously. I have suspected my pump since it seems to be getting more and more noisy.
What brand of fuel pump do your have. If it is a Walbro, they dont like PWM. Try changing this. Go to the Pro Tuning Menu,and select Fuel Pump Control. Change PWM Low Flow, PWM Mid Flow, and PWM High Flow to 100 % and also set Volts for Pump on from 9 to 19. This makes the pump system turn on, no matter what, and actually takes the PWM load off the circuit
I have an AEM 385 lph external pump. I believe I had the pwm all set to 100% before I did the reset the other day. I have an electric fuel pressure gauge coming today that I will use to see if I am loosing fuel pressure.
Not that I'm recommending to change this right away, but I would at least look at your secondaries linkage and see if there's any delay (even a small amount) between the primaries and secondaries opening. Your issue may very well be tune-related, but I fought a similar issue for longer than I'd like to admit, until reading a thread here where someone else had one out of adjustment. The only thing Fitech would tell me is turn up the accel pump, etc...
I did take a look at the secondary linkage and took out as much slack as I could. Definitely was some there but it didnt help the lean issue. I got my fuel pressure gauge on it, and I am only getting around 30-40 psi at the throttle body. I am researching new fuel pumps now, and am leaning towards switching to an in tank setup since my external pump seems to be going bad after 1.5 years and maybe 5000 miles
Definitely recommend in tank fuel pump and go with a quality pump that is made in the USA such as Walbro. 30 to 40 psi is too low. Also check/clean or replace fuel filter with a quality filter.
Sorry to hijack this thread but I have not been able to create a New post. I can't find the link to it. I can only reply to existing posts. Anyone else having the same issue?
EDIT PS: ignore. Sorry for the momentary lapse of reason!
So I got my holley sniper drop in fuel pump unit installed, and my fuel pressure was no different. I plugged the return port and got 100 psi, so I figured out the pressure issue was actually the pressure regulator and not my pump. I installed a 4 bar regulator and am getting a consistent 50 psi now. The lean issue has not gone away though.
A few weeks ago I also had an injector get stuck open. Is it possible that maybe I had something go through my fuel system and clog an injector and screw up the regulator? Maybe also some other injectors are screwed up and not firing correctly? It would just be odd if that is the case since it is only an issue at that one specific point while driving.
While the logic of getting a new pump is sound, and I like the in-tank pumps if for no other reason than they're quiet, I'm just wondering if that's really the issue. I remember reading the Mean Street uses lower pressure injectors than the GoEFI 4 600 (my system) that uses 58 PSI so I checked and found this on page 35 of the FiTech 2020 catalog:
"What fuel pressure does the system run at?
Our Throttle Body Systems are rated at two fuel pressures; 43 or 58 psi.
43 psi - Go Street and Meanstreet
58 psi - Go EFI, Power Adder and Easy Street"
If that's the case, then at idle you'll see lower pressure because the system lowers pressure at idle because it's not required. My pressure is right around 50PSI at idle, but runs great. Another problem might be the pressure regulator itself bypassing too much fuel if you're really in the low 30s. I'm sure there's a way to check this. In any case, a new in-tank pump is s great investment! Good luck!