p0172 and stalling issue
 

My car started throwing the code p0172 last Saturday. I used a code reader to figure out what it was, and to clear it. For those of you that don't know, it is a code for system too rich. I have been getting the code about every 40 miles now for a week, and finally had time last night to do something about it.
I cleaned my filter, and maf. I also changed my plugs. I reset the ecu and let the car idle a while. I took it out for a ride, and the issue resumed. The car really is running rich according to my wideband, occasionally hitting 9.8 afr at about 0psi. The problem seems to be while cruising at about 0psi. If I am drawing more vacuum or am in boost, the afr's are closer to correct (14s for cruising 12s for boost). Up until last night, the car was throwing codes, and acting a little squirrely when it got rich, but nothing unbearable.
I went out to the bar last night, and the car started acting a fool. Every time I stepped on the clutch, the car would die. It stalled about 5 times on my drive home (sober, don't worry). I have to say it was raining last night so that might have helped the problem as my evo does suffer from the rain gremlins.
This morning was the kicker though. I went to start my car for work, and it would not start. I managed to get it to start by pressing the gas when I turned it over, but the moment I let off of it, the car stalled. This happened three times before I decided to take a different car to work. I am going to do a leak test today with the homemade intercooler pipe pressure tester that I am sure alot of you are aware of. Do any of you have any ideas as to what could be causing my sudden and unexplainable driveabilty issues and code?
Should I attempt to replace the front o2 sensor or Maf first if it does not turn out to be a boost leak?

p0172
 

Sounds like you have a Friday special evo:(. Well i would do the same thing you doin checking for boost leaks because that what it sounds like it could be? Or maybe a TPS? Might be a stretch thinking TPS? Also your afr's running 14s crusing sound right but 12s sounds lean under boost for your evo:crap:. Do you have a tune? I was thinking that should be more like low/mid 10s or high 9s evos run RICH. Let us know how the boost leak test went. :mitsu:

I found a source of one of the problems. I had a HKS EIDS installed, and some of the wires had come loose on the EIDS/ecu connections. I took off the EIDS and soldered the ecu wires back together. Now the car starts. It still is suffering from stalling at random as well as rich conditions at 0psi. I was not successful in making a boost leak tester yet, so I will do that today and post results.

From my experience with other cars, it is a faulty O2 sensor. It causes the ECU to think it is to lean so it tries to correct the problem by adding fuel to compensate for the problem.

My .02

That is encouraging to hear. I recently bought an o2 sensor and will be replacing mine tonight. I just hope the evo vii and evo ix use the same one. Hope that fixes it.

P0172 code usually is a boost leak with turbocharged cars. It could be the 02 sensor as well

faulty o2 sensor , on my car i replaced the front 02 and , it got fixed

How quickly and catastrophically does an o2 sensor fail? My car was fine and all of the sudden one day while I was driving to Charlotte the cel came on and my car was running rich. I didn't do any work on the car or anything, it just happened when I was highway cruising, experiencing little to no boost.
What size pvc cap are you guys using for a boost leak tester anyways? I bought the 2.5" rubber hose, and the directions said a 1.5" pvc cap,but it is way to small to fit in the rubber hose and clamp tight enough to form a seal. I hope I bought the right stuff. I got 2.5" rubber hose (stick hose from NAPA) and a 1.5" white pvc end cap.

Been there done this.... When you said that when you pressed the clutch in the car died it hit me... My car started off throwing the system to rich code and then progressively got worse to where it would die when i would push the clutch in. After trying to diagnose the issue for about 2 weeks the peddle started to fall to the floor after hard accelleration... It ended up being crank walk. :( I would have it checked asap to make sure this isn't happening!

just to let u know , if i were u id change the oil asap when u change the o2 , cause if its the o2 and u have been very rich ur oil is contaminated by been so rich

Thanks gfng, that is good advise. Luckily I am due for an oil change this weekend so that will be done as well. I am praying it is not crankwalk. I thought that was a dsm issue that we got over?

no it shouldnt be crank walk , do u have ecuflash ?? if so u could be able to see how the o2 sensor activity reacts , it should get stuck rich if its damage ...


if it were crank walk , u would have noticed by the belt , since the crank wants to take a hike it unbalances the belt and u can see tear and wear

My first sensor went bad at 50k, only 3 days after getting tuned and running perfectly fine. The sencond one went bad 4 weeks after replacement and running fine.....then all of the sudden it took a crap on me.

take it to a shop

front o2 sensor replaced, as well as plugs gapped and changed. No different than before, still wont start unless gas is held, and cant idle. I am going to leak test it today, and hopefully get to the bottom of it. I do have ecuflash and am going to try it out as I have never used it. I bought the cable but never plugged up. I spoke with the previous owner who happens to be a former mitsu tech and he was almost certain it was a boost leak. He said leak test and remove and visually inspect all connections for any signs of wear or leaking.