I've read through everything I could find but am still confused and unenlightened. My own fault I'm sure.

I installed the PFC and am running the base mod map. I will have a tune next month. Stock except for intake, dp, catback. I don't have a wideband yet. I have O2 feedback ON.

When coming up to a stoplight, with very low throttle, I get a bucking at around 1500 rpm. It is really annoying. I have fuel cut at 1300, 1400, and 1500.

Any ideas as to what I might be able to try to reduce this?

 

It's most likely lean. Timing can effect that as well but since we're guessing I'll say fuel.

 

How old is your 02 sensor?

Turn off o2 sensor FB and adjust manually your idle. Also if you have fuel cut, raise your F/C values in the settings menu.

 

Well, I'm such a noob that I wouldn't trust myself to adjust fuel or timing at this point, particularly without a wideband.

Good question on the O2 sensor. It was replaced 2 years, 18k miles ago.

I wasn't clear, I don't have fuel cut, but in Settings 1, REv idle, I have the F/C A.E, E/L, and A/C set to PFC to 1300, 1400, and 1500.

 

Fuel cut is when the engine like suddenly start to break up and then keep going up in rpm's?

like brm1,000mmmmm2,000mmmmmmm4,000brmmm4,000brmmm4,000 brmmm5,000brmmmmmmmmmmmmmmmmmmm8,000?


Only does it at half throttle...

 

TRUE ecu fuel cut only happens at the set rev limit or at the set boost level limit. Both are PFC controlled.

Any other fuel surging is not fuel cut, but a fuel or tuning problem.

The FSM list some fuel tests to insure proper fuel delivery. When was the fuel filter last changed?

 

A long time ago. I will buy a fuel filter during the week them to be safe. Car needs to be re-tuned to solve some issues like being WAYYYYYYY to rich. I'm completely aware of that.

 

Are your TPS voltages in spec? If the PFC thinks you're completely off throttle, it will have the injectors off above 1500rpm. You might feel them come back online below 1500. But I'm not sure what other issues would increase bucking at that time...

 

Yeah, I'm thinking a tuning problem since I didn't experience the bucking with either the stock ECU or the Pettit Unlimited ECU. I had the fuel filter changed (yeah, I didn't do it myself), about 2 months ago.

I don't know about my TPS voltages. I suppose that is something that I should check. I'll dig out the FSM and see what it tells me.

What would happen if I increase the rpm value in the Settings 1 Rev/Idle section to higher than 1500? Might that make it better? What happens if I lower it back to the base map, 1000, 1100, 1200? Or should I just make the change and see what happens instead of asking silly questions?

 

The 3 F/C values are labeled FUEL CUT but this is really wrong. They are the points when off throttle fuel cut stops and the injectors come back on to control idle. If set too low, the idle my drop way low before it stabalizes or go dead. The DASH POT works along with this to allow the idle to stabalized when you quickly close the throttle.

It is all described in the FSM and PFC manual.

 

Thanks Chuck. I was a bit confused because when I read the PFC manual, it described what you just did, but when I was reading through some old threads from a search I seemed to get some more obscure information.