Lean under minimal throttle
Your new post came in while I was writing mine...As your post states, it wasn't a fuel pump issue, but instead was a regulator issue. You may want to check with FiTech (or just Google) to see what impact forcing the higher pressure on your injectors has. I know the injectors on the MeanStreet are rated for lower flow than those on the GoEFI systems...but the MeanStreet has 8 of them. There was a thread somewhere about folks changing the regulator hoping to increase the HP level the units would support by forcing more fuel through the injectors (through the higher pressure). In any case...glad your issue was resolved.
My fuel pressure issue is resolved, but not the lean condition. It seems to be mainly on return from higher rpm and a quick raise of the throttle from 0 up to about 5 percent.
I'm having the same issue where it's fine off the line and easing into the throttle, but when I'm coasting and ease into the fuel, it goes super rich. I tried adjusting the DFCO and the fuel return, but it works perfectly on a hard decel where it cuts fuel and I'm at 20 AFR. It's when I'm a light coast where DFCO doesn't really kick in and I ease back in, it shoots up to 16+ AFR. If I give it some more gas it comes back, but it's super annoying that it surges every time this happens. I asked FiTech weeks ago and haven't received a response.
Thanks, Matt
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Quote from redriderjf87 on June 3, 2021, 5:26 pmNot 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...
regarding your suggestion- i too found that thread and found a really small amount of delay to the secondaries.
so i adjusted the minimal amount i could (which was 1 turn clockwise). it got rid of the slack - but without noticing it right away - it introduced another issue - my RPM would go higher than programmed (and wouldn't go lower no matter what I tried in the tune).
I suspected a vacuum leak and tested many possible issues - but the issue was the secondaries were forced open ever so slightly .
I returned the adjustment to "factory" - and the RPM was as expected again.
so what i wanna say is:
a small amount of delay is acceptable, otherwise, other issues may arise.
To add to the original post - if you adjusted that as i did, it may be contributing to the issue..
So i did a couple things and they seemed to help, with a final adjustment I think it is good now. First I turned all 8 injectors on all the time. The software has it running on 4 up until a certain rpm level. Then I backed a little primary out at idle, and added some secondary back to get the IAC steps correct. That helped alot up until around 5 percent throttle. I found that my secondaries were not opening until after 5 percent throttle, and it was at that point it was going lean. I adjusted the linkage so there was no slop, and now it seems to be fixed.
A couple of things, There is no Primary and secondary's. It's not a Carburetor. They are Front and Rear, Now think about how it works....... The TPS sensor is on the front throttle blades, It doesn't know what position the rear blades are sitting at so ALL 4 throttle blades need to be sync'd together with the adjustable linkage between front and rear. NEVER use the rear idle screw!!! Only use the front idle screw to set the IAC. If the rear idle screw is used to set the IAC the TPS sensor doesn't know its position. for example the front blades could be closed more than the rear and the TPS is telling the ECU to deliver the amount of fuel it requires but because the rear blades may be opened more so will be allowing more air into the engine which will cause the engine to run lean.
As for the lean spot at light throttle I've been chasing mine for 5 years and haven't be able to fix it lol
Here are the instructions (from Fitech) on how to adjust IAC at idle by turning front and rear screws:
Start with the engine off and key does not need to be on.
1. Disconnect the throttle peddle from the throttle body, so we know it is not moving or holding the throttle.
2. Unscrew both front and rear adjustment screws so they just come off of the pivot arm stop.
3. Starting with the front screw, screw the adjustment screw in until it touches the pivot stop and you just see the throttle arm/blades just start to move. Once you see this movement screw the screw in ½ turn (If the engine is pretty stout go ¾-1 turn in)
4. On the rear screw we are going to do the exact same thing, screw the adjustment in until you see it touch and move then go a ½ turn (If the engine is pretty stout go ¾-1 turn in)
5. This will set the blades close enough to start and warm up for final adjustment. We just want the engine to idle, if it is high that is ok until it warms up if it is low and wont idle go in a small amount on both screws until it will idle.
6. Turn the key on do not start, at this point we want to clear the leaned data that the car has learned previously this way we can have a clean slate when we start. Go to Go-EFI Initial Setup then go to Reset Learn, inside reset learn go to Reset IAC Data by switching the 0 to 1 and hit send to ECU. This will erase all leaned data but will not change any of your base settings. Turn the key off for 30 ish seconds.
7. Start engine and let it warm up to 170 degrees F then look at the IAC steps on your dashboard. With the engine running and the temp at or above 170 adjust accordingly. If the IAC is above 10 you will screw in both screws equally until the IAC steps falls below 10 but does not sit on zero. If the IAC steps are staying on Zero and the idle is above the desired setting you will unscrew both screws equally until the IAC jumps back and forth from a number under 10 but not staying on zero and the idle is at your target RPM.
8. While you are making your fine adjustments keep an eye on the TPS value, if it goes above 0 shut the engine off and let it sit for 30-45 seconds. Turn the ignition back on and go into Go-EFI Initial Setup then go to reset TPS Learn, inside reset learn go to Reset TPS Data by switching the 0 to 1 and hit send to ECU. Continue with the throttle blade adjustment.
9. Reconnect the throttle cable/rod.