What would cause my car to run great one day and stupid rich the next? This has happened a few times now

 

Odd. Stopped at canadiantire returned something come fire up the car and it runs great err. Il post a during rich and a normal day log later tonight

 

here are my data logs one of rich and one is ok with close to good afr

 

Now I've had the opposite, car runs great pulls hard afr are ok hit boost let off try and hit that bin once more while I'm data login, afr are now in the 16-17. I let the car idle as I was coasting then I could hear my power inverter buzzing a tad as in low voltage? Then my head lights got bright when bright buzzer stopped so I hit the gas afr are good. Looked at the log I could my bat voltage drop to 10v or so as the cat start its lean cycle, then when voltage hits 12.5 all is well afrs good. I know that are areomotive fuel pump is power hungry.Il correct my charging problem and repost!

 

If your battery voltage is swinging between 10V and 12V, I don't even need to look at the datalogs to determine the problem.

At 10V everything is struggling. Fuel pressure will be too low. If injector battery compensation is not tuned, then the injectors will be lazy as well. Combined with lack of fuel pressure, that's lean.

If you are only charging at 12V anyway, something is wrong. Bad alternator, bad regulator, incorrect wiring, etc.

S4 alternators SUCK. They were underpowered and overloaded from the factory. Upgrade to an FD or Taurus alternator.

Do NOT run into boost with the car like this.

 

OK so I fixed my voltage issue with the car on cold starts it's still really rich even after my Cold start enrichment is offalthough it did save my *** today some ******* cut a curve and I just about run into you have a good that my car wasn't any faster

 

MAT?? i had this set to zero, i have now dropped to -4 for most of the range untill 160 its -3 and zero above that. seams to have fixed this prob.. tho i need to retune by looks of things.
when i take the car out tomorrow il see if this fixed my problem

 

Don't tune the MAT until you have the rest of the settings fixed. Actually I fine only slight adjustments are needed to MAT.

If it's really rich on cold start then it's the warmup enrichment which needs to be adjusted, as well as the after start. If you are pulling the warmup to - for the first few seconds then that's the afterstart making it too rich.

 

ok my real problem was a vacuum leak at the squirt, some how i managed to hear a slight vac sound, i inspected and found a crack on my vac line... fix that and re tuned most of my map fix now.. hope this helps the next poor guy lol, i did adjust mat one notch -1 all all ranges up to 160 and seams to be best.
WE is better that ever as well. funny how much different my tune is compared to my last S5 build!

 

Well then, that will do it as well. I recall Sam having a similar issue that resulted in weird symptoms. His vacuum line to the 'Squirt had filled with oil.

 

o yes i do remember that :0 in the middle of nowhere ville USA Lol

 

I think I'm going to update my writeup to recommend a vacuum isolator on the MAP line if the 'Squirt is mounted below engine level, or at the very least to loop the line above the intake manifold level.

Anyone running a turbo will get oil into the manifold, as will running PCV. A shocking amount of oil, actually.