Hi Everyone,

Between -5 psi (vac) and ~+5 psi my Evo 8 will go "super rich;" according to my UEGO it is <= 10AFR. As far as I can tell is not connected to hard acceleration or simply giving the car a little more gas, either case will result in this rich condition (but only between ~ -5psi and ~+5 psi.) If i let off the gas, and vacuum drops by lets say as little as -1psi to -6 psi, the AFR goes back to normal range of 14.7 - ~15.3.

On the boost side as soon as i get over ~5 psi (maybe around 7-8psi of boost) the AFR values begin to reflect what they should be during normal boost condition (for me they go up rather quickly from the 10AFR to 11.x, and then gradually even out in the mid 12s.)

I've been trying to figure this out for quite some time and really can't come up with a satisfactory answer; its more annoying than anything else because I just see it as a waste of gas. Furthermore I noticed several evolutionm members that appear to have similar "car goes super rich" / "DTC P0172" problems and I would actually like to try to solve this. (assuming that this is the exact same problem that they have; its always Evo8s too.)

Things I've tested, observed and considered:
1. MAF - cleaned and tested with a new MAF, no effect on rich condition.
2. Fuel Pump - tested with factory and Walbro 255, no change
3. Fuel Trims - the ECU is constantly trying to take away fuel, occasionally the max of 25%
4. Fuel Pressure - appears to be normal
5. MAP - tested with a new factory MAP, no change
6. Injectors - (I have stock Evo 8 injectors) ... haven't yet attempted to try new injectors. (Perhaps the injectors are causing this?)
7. Vac leak - tested and no leak was found.
8. ECU's Fuel Map - tweaked and tested to see if i can get any change, no luck
9. Using stock or after-market intake, no change
10. CAT or no CAT, no change (the rich condition is actually the reason I removed the CAT; I don't want to damage it and have to buy a new one when I need to smog the car)
11. stock or after-market turbo-back exhaust, no change.

I guess that's all that's worth mentioning ... but I'm sure that I missed something, let me know and I'll try to fill in any blanks.

Thanks!

 

Just wondering if you find your problem yet? I also have the p0172 code. Wondering if i take it to the tuner they might be able to tune it out.

 

My car still has this rich section that I described above, but after swapping out the injectors (and rescaling) the P0172 went away, so far its going on 2 or 3 weeks without the code coming back ... I guess the injectors were just in bad shape.

Probably, instead of buying new injectors you can get them cleaned and flow tested at http://www.witchhunter.com

Hope it helps, I know how you feel ... damn System Too Rich (but definitely better Too Lean) :-p ... If you need it fixed ASAP (to pass SMOG, etc) I would recommend just disabling P0172 in the Periphery Bit table

 

what is everything that i need to disable it? Some kind of software and a cable? Would you know how much it cost by chance?

 

I'm not really sure how familiar you are with tuning, using ECUFlash, or if the words "Periphery Bits" mean anything so I'll start at the beginning

Tools/Hardware:
1. Tactrix Openport 2.0 cable + Mitsubishi reflash adapter (dont forget to select the adapter off the the side) Cable+adapter = $179

Software:
1. ECUFlash

Knowledge:
1. General ECU info and tutorial (the videos in the 1st post are an excellent source of info about tuning via ECUFlash)
2. Adding ability to disable p0172 through ECUFlash (and many other OBDII codes)

Hope you find this helpful ... feel free to send me a PM if you have any questions.

 

thanks for the info. I have the original tatrix subaru cable. would that work or is it evo specific.

 

The tactrix cable (the OBD II) plug is the same for evo and subaru ... the only thing that you will need to is the correct reflash connector for evos or WRXs