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Power FC surging/hunting idle after warm up

maximajim

By maximajim,
in Engines & Forced Induction

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maximajim Community Regular

maximajim

Posted
Posted

Hello,

I recently installed another Q45 TB and TPS. The PFC will now hunt for idle after warm up. Goes 800-1500 rpm surges. The standard ecu does not do this nor does it have a code. However the standard ecu does idle higher than before. What is the hunt an indication of? TPS volatge is ~0.60V at idle. Base timing was checked at 20.

Thank you.

the phantom Collaborator

the phantom

Posted
Posted

I remember a while back when sorting some idle problems on my RB25/30 DET R33 with PFC, that at a certain very minute openning of the throttle, just passed closed, I could induce this same hunting condition repeatably. I also came to the conclusion that the idle control algorithm of the PFC was inferior to the standard ECU, but I managed to fix it eventually after much hair pulling.

What engine are you running ....RB25,26...I cant really see clearly from your avatar? The 26 has a throttle switch as well as a TPS, wheras the 25 only has the TPS. I assume you have the correct PFC for your engine? What AFM are you using? Have you removed the screens etc?

  • Like 1
R31 POWER Mentor

R31 POWER

Posted
Posted

Fiddle with the setting in the rev/idle screen.Write down what it has standard so you can always go back if need be.

Here are my settings even thou it's a RB20det

f/c - 1270

f/c - 910

idle - 870

idle - 800

maximajim Community Regular

maximajim

Posted
  • Author
Posted
I remember a while back when sorting some idle problems on my RB25/30 DET R33 with PFC, that at a certain very minute openning of the throttle, just passed closed, I could induce this same hunting condition repeatably. I also came to the conclusion that the idle control algorithm of the PFC was inferior to the standard ECU, but I managed to fix it eventually after much hair pulling.

What engine are you running ....RB25,26...I cant really see clearly from your avatar? The 26 has a throttle switch as well as a TPS, wheras the 25 only has the TPS. I assume you have the correct PFC for your engine? What AFM are you using? Have you removed the screens etc?

It's an rb25 with rb25 pfc. AFM is standard and untouched. I have a feeling the pfc just doesn't like the new tps. I have reset the pfc to no avail.

funny thing when setting the TPS i had a voltage of 1v at the sensor using a meter but the fc datalogit screen would show .65v. I have corrected the snsor voltage but no change.

DRFTR33 Contributor

DRFTR33

Posted
Posted

the problem you are having sounds like a badly adjusted throtle position sensor, who did the install

also check your idle speed on your power fc if it is to high you will hit the idle limiter and it will also do the exact same thing you are explaining

  • 8 years later...
Jayden.K Collaborator

Jayden.K

Posted
Posted (edited)

I remember a while back when sorting some idle problems on my RB25/30 DET R33 with PFC, that at a certain very minute openning of the throttle, just passed closed, I could induce this same hunting condition repeatably. I also came to the conclusion that the idle control algorithm of the PFC was inferior to the standard ECU, but I managed to fix it eventually after much hair pulling.

What engine are you running ....RB25,26...I cant really see clearly from your avatar? The 26 has a throttle switch as well as a TPS, wheras the 25 only has the TPS. I assume you have the correct PFC for your engine? What AFM are you using? Have you removed the screens etc?

How did you fix it, I installed a bigger turbo and type b tomei cams and I have a constant hunt at 900-850rpm under, so I have the idle higher to stop it but if not hunting runs rough on idle. Tuner could not tune it out, replace afm and made it better but not fixed. Adjusted tps to correct position and base timing is 15deg

Edited by Jayden.K
89CAL Grand Master

89CAL

Posted
Posted

Fix TPS, you may need to do a data init and do the idle re-learn, which shouldnt be a problem if you have datalogit.

As suggested above play with the idle settings, this is easier to do in FC-Edit as you can adjust them more then just on the unit itself

If you have a wideband (or even without one) try to richen the tune up around the idle cells. Easier with a wideband cause you can aim for around 14:1 AFR (they seem to idle a bit nicer around here) and play with the timing. Mine runs better at 20 degrees all around idle

Jayden.K Collaborator

Jayden.K

Posted
Posted

Ok sounds like I need to hit my tuner up again for that idle learn. As he believed it was something else. I tried mucking around with the idle screw with the solenoid unplugged but made no difference. Cleaned my earths up and made no difference. Removed my idle screw and was fairly clean. I tune with a wide and bit run a narrow band. I have been thinking my fc is cactus. But I'll ask my tuner he is not one to skip corners

paulr33 Grand Master

paulr33

Posted
Posted

you dont need datalogit to do DATA INIT

but you will loose the tune, so if you don't have a copy or have it saved then yes get datalogit and back up the tune first

there is a procedure to follow when you do DATA INIT

and if you dont do it properly the idle is ass and sometimes results in instant-stall skyline

so read the pfc faq on DATA INIT at paulr33.com

if the TPS is wrong or off scale and isnt in the idle range then the if may tell the PFC the throttle is actually partially open, when it isnt

so as the others have said, dig up the nissan spec manual, find out the voltage range the TPS should be for idle and set yours to match that

the PFC will copy what the standard specs are so ensure it is aligned to that

ie if the spec manual says idle or closed should be 0.035 v then make sure yours is the same

jhjones Rising Star

jhjones

Posted
Posted

It's an rb25 with rb25 pfc. AFM is standard and untouched. I have a feeling the pfc just doesn't like the new tps. I have reset the pfc to no avail.

funny thing when setting the TPS i had a voltage of 1v at the sensor using a meter but the fc datalogit screen would show .65v. I have corrected the snsor voltage but no change.

Wiring?

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