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Fitech tuning... acceleration issue

steveh326

steveh326

Active Member
hi guys, been working almost 7 days a week and haven't been around much to bug you, but need some help now.

had a chance to get the mustang out for a little ride and having issue. When cruising along and either rolling on the throttle or punching it, have a severe hesitation. when doing this at highway speeds running in 5th gear, like to pass someone, it actually bucks and refuses to accelerate.

Here's the part I don't understand... when this happens I get a real strong gas smell, which made me think my accelerator pump was shooting too much fuel... but according to my fitech display, my AFR goes up to 20.0, indicating a lean condition...

any thoughts or suggestions?
 
This is the one issue I have as well. To be honest I haven't really tried to figure it out. I suspect it is a lean condition in my case (and probably yours) given my heads and cam. There are a number of tuning adjustments that can play a part. I suggest you turn on the data logging and make a few runs that will cause the issue and see what the data tells you. You can share the log with FiTech and see what they suggest. AND SHARE it back here. Save me the trouble!

BTW, don't expect to hit the throttle hard at highway speed in fifth and get good response. The gearing works against you. That's when you down shift same as an auto trans would do.
 
The FiTech unit controls the pressure by regulating the fuel pump voltage. It would/will give an error message if pressure falls too low. What he is describing is pretty much THE "classic" FiTech issue.
 
I have heard that the ECU sit in the "carb" so a heat problem is possible I guess ??
 
I mean due to heat , the ECU can't operate properly iow its program is "froozen/hang up. ??
Still I would check the fuel pressure.
 
It's a tuning issue. Not heat. Does it at all temps. Like I said, all FiTech set-ups I've ever read about or encountered face the same issue. I ran into a guy this summer with a mustang and a FiTech complaining about the exact same issues as I see. He gave me a guys number who he claimed was able to dial his in that's not too far from me. Might give him a call soon. I wanted to get it up on a dyno anyway as that's the best way to really go about it. The challenge on some of the early units like mine though is they do not allow as much program tweaking as the newer models. I'm thinking hard about a newer system install.
 
I'm gonna play around with it and try some diff scenarios to see if I can figure it out. I know my intake is on the big side for this engine (bought it with the stroker in mind but haven't gotten there yet) so the it may be part of the problem I dunno.

I also have a guy here in town that may be able to help I might reach out to him tomorrow.
 
called Fitech support this morning... He said the ECU is seeing the lean condition and then pumping more fuel into it to compensate, which is why I get the strong gas smell when it occurs.

he said 3 things to try/check...
- try richening accel pump by 10 and see if that helps
- install fuel pressure gauge to confirm proper fuel pressure
- check for exhaust leak at/around the o2 sensor, which would cause a lean reading

since my AFR is perfect at cruising speed, I am going to try adjusting the accel pump first. I need to check my header bolts anyway so will do that also.
 
stupid question for fitech owners...

when I make a change and send it to the ECU, does that change take affect immediately, or not until the next time the car is started and the map loaded? I swear, the car ran better yesterday after I had it parked for a week, so I started wondering if the maps I was updating were getting loaded. before, I would make a run, pull over to the side of the road, adjust the setting, send to ecu, and pull back out onto the road for another run. doing that, I did not seem to much difference, if any... which got me to wondering.
 
Once sent to the ECU the change is immediate.

What changes are you making? Since I last commented here I finally got off my ass and spent a little time in the car trying to tweak away some of the issues I had been living with and had quite a bit of success. No more "popping" on deceleration when downshifting. I've almost completely eliminated any hesitation and/or bogging on quick pedal romps too.
 
I also noticed that depending on my driving habits I could develop a gas smell too. After logging quite a few trips of various driving styles I was able to go back and make some changes to my AFR settings and a few other things that resulted in slightly better "seat of the pants" feel while also leaning things out a bit and eliminating the gas odor.
Amazing what can be accomplished when I finally decide to actual do something! After all of this I am keeping things as they are. The unit I have gets the job done to my satisfaction. I will still get the car up on a dyno and let an expert play around a bit more at some point likely but its no where near the top of a to do list anymore.
 
I thought the changes were supposed to be immediate but was not positive.

I was increasing the accelerator pump to try to get rid of my severe lean condition when accelerating. wasn't seeming to make any difference... but yesterday when I drove the car again the issue seemed to be way better, which had me wondering. I didn't have the gauges on, but the car didn't have the severe hesitation nor the raw gas smell when romping on the gas pedal.
 
There are a number of adjustments that affect lean tip-in on quick pedal hits. If you just press into the pedal hard it usually does well. If you stab it hard and quick its a whole other animal. The latter is where you will need to make quite a few changes, I would guess. I did.

When adjusting the Accel Pump values make sure you are adjusting the FAST portion not the base Accel values. Those are for slow pedal acceleration which is not your issue. Also need to bump up the values on the dTPS gain and max. These are how the system reacts to pedal movement. Gain is like a sensitivity adjustment on a motor control board, if you are familiar.
 
If you can access it with your system, another good thing to adjust is the PWM Threshold RPM. It's likely set at about 2500 or so. Dropping it down to about 1500 will make sure the fuel pump keeps the pressure up under hard acceleration.
 
How many miles do you have on the system? It takes a bit of time to learn. I'm at about 2500 and last I looked it still showed areas that hadn't reached a high percentage (low values indicate more learned) of learning.
 
actually I was experiencing the issue both with slow pedal movement (think passing someone on the interstate) and fast pedal movement too.

my unit is older, I am not sure I have the settings you are describing, but will go back and look.

I only have a few hundred miles on the unit so far, so it probably has more learning to do.
 
You'll have them with likely the exception of the PWM. If you want to go through the hassle of a software upgrade you can likely get it too. My unit is like 8 years old and is one of the first generation put out and it has all the others I wrote about.
You should not just watch your large gauges when driving you really need to data-log and go back home and take a look at all the data on your computer. Much easier to see how things are adjusting, etc. You can also save those logs as spreadsheets and share them with FiTech or online to get expert guidance on how to proceed. That's likely my next step to finish things up.
 
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