C32owner

I remember reading sometime back about the issue of the car's ecu suddenly running on a lean map of sorts after doing a pull. I cannot find that thread now where I think the guys had figured out, this was happening under certain conditions and I am trying to find what that situation was. I seem to think it was when the car was under high boost? Over 17psi when the ecu would get locked into a certain map and then the AFR's would be super lean when under acceleration. My car did this tonight for the first time ever, I was doing some data logging and after about the 5th pull, she just ran horribly as if there was a mis. Checking out the live data first thought was fuel rail pressure but that was still fine even under load, but then noticed the AFR was scary lean.. So glad I have my data available in front of me always. Things could have gotten very expensive. Anyway the usual trick of pulling over and restarting the car reset the ecu and she was happy days driving home.. Guys with better memories out there than I, do you recall the thread talking about this change or locking into the map that sets the car lean under load?

SICAMG

That was me ....I believe unless you read someone else's post.
Random lean spike that stays locked in until you shut car off for key cycle and yes fuel pressure was on the money.
I ended up putting a map clamp on and set it to 4.3 volts. this way if the ECU ever see's a "funny" off the scale output/input reading which normally pegs the map reading, it will no longer do that.
One thing that I swear by is the AEM fail safe. I have it set at 12.1 AFR so any reading over that the compressor will become disengaged. There is no way to "blow up" your engine do to a lean out and you never really have to pay attention to anything while beating on your car. Has saved the day 3 times since I bought it. No brainer!!

C32owner

Indeed it was you thank you Sir for responding. Just to clarify when you say fuel pressure was on the money? Did your fuel pressure drop to low in a pull or under load so then the ecu locked into this "lean map mode"? You speak of a map clamp so now I'm thinking you actually meant it was a boost spike of over the MAP sensor limit. Just trying to get to the bottom of my issue that was experienced tonight, as there is no ways I hit a map sensor limit of I think it's at around 17psi..I'm at 5500ft altitude and my boost is only 9psi at the very most. So not sure what triggered this locked lean mode

PieRat

Hey mate. I had the same thing, you will start getting this more and more often i think. What you have is a an air leak. Mine was the metal pipe that goes into the back of the surge tank on the right hand side if you looking at the engine. Its the line that goes over the valve cover to a charcol canister or whatever at the front of the bay. Its a common leak so check that one first by spraying some brake cleaner or throttle/carb cleaner where the pipe goes into surge tank, if the cars idle is affected by this means there a leak..

PieRat

Forgot to mention when i had this it would drive fine 99% of the time, the ecu notices parameters are oftebout of whack (maybe only under certain conditions, for me it was cruising) then changes to some backup map or some sh*t and car is all out of whack until you restart it. Mine was doing it more and more often as the leak got worse i suppose.

E55amg0220

This was me too i had this bad an wrote many posts about it. But mine drove perfect 98% of the time and when it happened it was on the freeway just cruising.

SICAMG

For a speed density engine it appears to be VERY sensitive to ANY leak at all no mater how small ! Our ECU's are very smart with this stuff.

C32owner

Awesome guys, thanks a mill for all the replies. Gonna check that pipe out for sure. I may have knocked it off a little when I took off my intake tube recently. That would explain it for sure. Thanks again.

Side note to SICAMG, the Aem fail safe gauge looks great and sounds amazing with the built in fail safe feature. I dig the sound of that. As a matter of interest how did you wire up the fail safe that the gauge sends the signal to shutoff the SC when you get into the lean scenario?

SICAMG

Simple. The AEM unit has it's own o2 sensor and will read real time signals and record them on your lap top. It will be a left to right scale on the screen. You then adjust YOUR scale that you want to be the upper limits of your recorded readings. So...lets say my recorded run hangs around 10.5 afr....which it does. I then adjust the scale to trigger the fail safe at anything leaner than 11.5 afr across the board.
The unit is wired directly, "relay" into the power line to the compressor clutch. As soon as it is triggered from the gauge it will interupt the supercharger signal and shut off the compressor for 10 seconds. After 10 seconds it will turn the compressor back on. The time is adjustable as well and 10 seconds is more than enough time to figure out "Hey? what just happened"
The unit is great and It's always on and set so you never have to think about it for any reason.

PieRat

Thats awesome mang! where u get dem they expensive?

SICAMG

Go on Ebay and punch in AEM FAILSAFE and it will pop up 287.00 is as cheap as I have seen and there is many on there.
It is a little pricey for what I use it for considering the gauge is wrapped in plastic and hidden under the ice box under the hood. I have data recording and a stand alone wide band so my AEM is only to serve as a fail safe only..

C32owner

Thanks so much brother, makes perfect sense. I can use that AEM kit on the other bank then to monitor the AFR's and have the built in fail safe. To brilliant! Thanks for sharing