The Top Mitsubishi Galant VR-4 Resource

Join the best E39A 1991-1992 Mitsubishi Galant VR-4 community and document your GVR4 journey.

  • Software Upgraded - Reset Your Password to Login
    In order to log in after the forum software change, you need to reset your password. If you don't have access to the email address you used to register your account, you won't be able to reset your password. In that case, follow the instructions here to regain access to the forum.

surging at speed

My recently acquired VR4 has a case of surging at speed.. it only has a narrow band light show installed, while cruising at light load, the car surges, and the surging corresponds with the car fluctuating from rich to lean.. its like its searching for something..


While cruising you should be in closedloop, where the AFR is swinging back and forth several times a second around 14.7:1. If the gauge is indicating rich, and then suddenly drops lean, that sounds like the ECU is trying to adjust the fueltrims but they are too far out of range. Do you have a logger?

check for boost leaks, my talon was doing similar, turned out to be a boost leak at the EGR valve

have a logger, its not wanting to download to my computer.. fuel trims are wacked out..

lft 134
mft 93
hft 86

SFAC2 was messed up, awaiting a replacement.
I will boost leak test her soon.

Thanks you

I pulled the stock O2 sensor, to put in my wide band.... it was way lean up top. I fattened it up with a SAFC. chipped for 720's and pulled 690's out of it... /ubbthreads/images/graemlins/banghead.gif

the funny thing is that when I pulled the stock O2 out, the at speed surge disappeared??

got to save some lunch money to get a new chip burned, putting in 850's, E85, and a 50 trim. It should be fun? /ubbthreads/images/graemlins/devil.gif
Last edited by a moderator:


Well-known member
Nov 21, 2008
Blackwood, NJ
Wow, that could have been bad lol.

Glad it's all cleared up. Did you get that logger working yet *nudge* or get the boost leak test done?
Last edited:

logger is out on loan.... /ubbthreads/images/graemlins/dunno.gif

the old turbo was smoking like a bug fogger, so we are also in the middle of turbo upgrade.
from 16g to 5031,
so making changes to the inter cooler piping, so the boost leak test will be in order
injectors from 690's to 850's, need to order a new chip.. I am tempted to run E85, but like the ability to burn dino fuel too.... dual image ?? thoughts?

I have a dead line, so this is getting done !!
Last edited by a moderator:
Support Vendors who Support the GVR-4 Community
Boosted Fabrication ECM Tuning ExtremePSI Fuel Injector Clinic Jacks Transmissions JNZ Tuning Kiggly Racing Morrison Fabrications RixRacing RockAuto RTM Racing STM Tuned

Recent Forum Posts

Recent Classifieds Listings