Quote from VintageSpeed2 on July 7, 2020, 9:38 am

I finally made some progress hunting down the lean tip in issue. I contacted Fitech after a year trying to solve the issue and asked for handheld update since Mclay up here shared his idea. Well they did not give me update but new instructions to adjust IAC and sync butterfly valves. Go figure that did not help at all. It just ran even worse.

Then I found a conversation on British V8 forums where one guy stated: "You are all running too lean AFR's. TBI EFI intake has to be wet at all times since it's not real EFI".

So I tried his suggestion and dropped my AFR from 13's to 12's and yes that helped a lot. No more lean tip in stumble. The AFR still goes to 13-14 after coasting but it does not stumble since it is not too lean for the engine.

I'm gonna run like this for a while and see how she learns.

Quote from sarkisi2 on August 10, 2020, 9:22 pm

Check the MAP gasket in the ECU. Most times it gets deformed and creates an issue. If you look at your log data and your MAP sensor data is relatively constant for a specific drive that's your issue.

Quote from redriderjf87 on September 6, 2020, 10:07 pm

It sounds like you're in the same situation as I was VintageSpeed.  I was at wits end, no matter what I did or what anyone said, there was no way I could ever get it enough fuel when stepping on it.  At one point I also went the route of just enriching my AFR targets when cruising which did help somewhat to give it a buffer of fuel on tip-in.

 

What I found after 3 YEARS of fiddling and guessing (no real help from FiTech's tech support - said to increase accel pump and then stopped answering my messages ) and receiving help from this forum, is that my secondaries were out of adjustment and not allowing enough fuel through at low throttle.  If your situation is like mine, I had the tip-in stumble really bad at 1500 rpm, and negligible by 3000.

 

I originally thought to check this, from a post stumbled on this forum ( https://fitechefituning.com/fitech-efi-tuning-forum-2/topic/secondary-adjustment/?part=2 ), and added my findings in that thread, as well as updated the last post of my NastyZ28 thread that Mclay linked.

 

** Rant **  It really does kind of bug me that FiTech tech support doesn't even mention this, as just a last resort if nothing else.  I get that they don't want to be liable for people screwing up their system, but sending customers an improperly adjusted product and expecting it to work without re-adjustment isn't much better.

Quote from PA_cob on December 26, 2020, 8:03 pm

I am having issues similar to what has been described in the above posts. I am running a 600 hp unit on my 289. When I accelerate from dead stop 1st gear climbs rpms no issues. When i get to second gear and the car is cold I get a stumble just above 2000 rpms. Almost like the car is running on 4 cylinders. That stumble goes away above 3000 rpms. Once the car is warmed up the it's not an issue but if I try flooring the pedal under 2000 rpms in any gear but first I get that same stumble likes it's missing cylinders. Above 3000 rpm it's fine, and this never happens in 1st gear. Also today I was idling and tried to slowly raise the rpms. I would get that same stumble between 2000-3000 rpms. My combo:

289 bored .040 over
Edelbrock RPM airgap intake
Trickflow 11R 170 heads
Trickflow stage 1 cam
1:6 full roller rockers
T5 transmission
Timing controlled by the FiTech
MSD two wire distributor

Quote from redriderjf87 on June 3, 2021, 5:43 pm

I'm going to make another post, since others mentioned it and after fixing my tip-in fuel issue, I have the same questions as others concerning tipout / DFCO.

Although I believe I've "disabled DFCO" (enable Temp 267, enable MAP 1.0, return MAP 2.0) and ensured my pwm is always 100 (thresholds set to 100, same with MAP and volt thresholds), I can watch the car go full lean anytime my MAP gets around 30.  So, anytime I'm coasting in any gear, or light throttle in 1st or 2nd.  Also, my rpm's drop Extremely fast between shifts, to the point it's impossible to match revs and I'm around idle rpm before I can get in the next gear.  I just ensured that my IAC steps are 7-8 when full temp, and I can crack the throttle from steady state without a lean/rich condition, so I think my TB is adjusted correctly.

I think this has been happening for a while, but I was always focused on the tip-in issue.  Not sure if anyone else has seen this issue of rpm's falling too fast?

 

Thanks,

Justin