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


https://www.miataturbo.net/attachmen...ine=1385613283
https://www.miataturbo.net/attachmen...ine=1385613283



Anyone have a similar problem? Throttle position sensor? Vacuum leak?

What fuel management system?

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?

This one FMU 12 1 Turbo Fuel Regulator Management Unit Purple Toyota | eBay

12lbs for every 1lb of boost.

^ 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.

He's implying you have aids. And aids are not good.

Pretty sure it has something to do with you mounting a flapper-door AFM upside down.

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.

Forgot to mention that I already flipped the afm back over. I have an extra on so Ill throw that one on as well...

I took the FMU off completely and unhooked the wastegate. It still running into the 10's while cruising.

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.

Solved
 

Boost pipe had a leak from a coupler.