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Old 11-27-2013, 11:56 PM   #1
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Default Bogging down while cruising. 9.5:1 AFR?

Ive been having issues recently with the car bogging down while cruising at a steady rpm. My wideband shows cruising around 13-14 then all of the sudden it will drop down to 9.5 10 to 1 and bog down a bunch. It literally throws you forward a little in your seat.

Other symptoms include:
Dying while idling
Engine cutting off from too low of an idle after revving and letting off


I am running a fuel management system and a timing controller. However this is under normal driving circumstances.

I was running the ecu off the widebands narrowband emulation, and I swapped it back to stock to see if it made any difference. It did not.

t25/28 turbo
only running 3lbs boost
1.6L - good compression 155 across the board
NB Injectors
JDM Sport FMU 12:1
MSD Ignition Unit







Anyone have a similar problem? Throttle position sensor? Vacuum leak?
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Bogging down while cruising. 9.5:1 AFR?-y7wpqt2.jpg   Bogging down while cruising. 9.5:1 AFR?-tgylpym.jpg  

Last edited by racoonfrenzy; 11-28-2013 at 12:39 AM.
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Old 11-28-2013, 12:27 AM   #2
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What fuel management system?
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Old 11-28-2013, 12:31 AM   #3
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I'm having a hard time finding your intro thread. You know, the one where you tell us about your car and your mechanical abilities. Perhaps you can post pictures of your cat?
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Old 11-28-2013, 12:32 AM   #4
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Quote:
Originally Posted by Screaming04 View Post
What fuel management system?
This one FMU 12 1 Turbo Fuel Regulator Management Unit Purple Toyota | eBay

12lbs for every 1lb of boost.
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Old 11-28-2013, 12:37 AM   #5
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^ would be the problem.

You're welcome.
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Old 11-28-2013, 12:42 AM   #6
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Quote:
Originally Posted by Screaming04 View Post
^ would be the problem.

You're welcome.
are you implying this?
https://www.miataturbo.net/diy-turbo...ger-fix-58692/

That does sound very similar. Im going to remove the fmu and see if that fixes the issue.

Last edited by racoonfrenzy; 11-28-2013 at 02:39 AM.
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Old 11-28-2013, 11:41 AM   #7
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He's implying you have aids. And aids are not good.
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Old 11-28-2013, 12:28 PM   #8
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Pretty sure it has something to do with you mounting a flapper-door AFM upside down.
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Old 11-28-2013, 12:34 PM   #9
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Classic AFM failure; upside down or not. Pull off the black cover, clean the area the brush rides on and push the brush down the shaft and tighten.
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Old 11-28-2013, 03:43 PM   #10
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Forgot to mention that I already flipped the afm back over. I have an extra on so Ill throw that one on as well...
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Old 11-30-2013, 03:00 PM   #11
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I took the FMU off completely and unhooked the wastegate. It still running into the 10's while cruising.
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Old 11-30-2013, 06:56 PM   #12
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If the AFM is defective and putting no signal or a low signal, the ECU is thinking that you are at WOT and adding fuel accordingly.

You would have that situation if the door is stuck open also.
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Old 12-01-2013, 01:21 AM   #13
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Boost pipe had a leak from a coupler.
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