Not to hijack but, I have to ask. Do you think that this temporary lean condition is a problem at idle? It happens to me at cold idle now and then. AFR will jump between 14.7- 18. I kinda figured that as long as the car does not stall, starts correctly, and as long as it only happens at idle that it is not worth addressing. Am I wrong here?

 

I haven't been overly concerned about it since the car isn't stalling.. as long as the ignition system is healthy, it'll continue running.. I haven't been able to sort out 100% why that happens, but its interesting that even stock cars have this happen in cold weather and I just never noticed it before.

Obviously getting rid of it is the best option, but until I figure out why the car swings back and forth like that at idle, its something I have to deal with.

 

o.k. jack, i studied your post and am trying to figure out the order of events. First, When you say unplug the o2 to force it into open loop, is this just to tune it or must it stay unpluged all the time??

1: unplug 02 closest to turbo.
2: make sure car is cold.
3: Start up car
4: Go to open loop menu on laptop
5: Adjust the stock injector size "higher"??
6: Save map
7: go to map 1 and add fuel in column 0 from 0-1500 rpm
8: Save map.
9: redo #5 & #7 till it idle good

O.K. What do you think????

 

Adjust it smaller so the car's maf reading is globally higher (just the stock injector scaling portion, leave the modified injector setting at 650 or so)

Don't forget, every time you change the injector scaling values, and save them, you MUST shut the engine off and let the ECU sit for a minute so the UTEC shuts down, otherwise scaling and other changes may not be in effect until its reloaded.. so it can be a little time consuming.. but your order is pretty much what I've done..

Once your happy with it.. Drive the car a bit and make sure it feels right.. Then reset the ecu, resetting the ECU (clearing the CEL) will also clear most of the fuel trims so it may run like crap again for a day, but it should finally run right and idle better.

The biggest problem is cams with alot of overlap, low engine vacuum and low exhaust output at idle allows the turbo to slow down airflow enough to screw with the MAF sensor, so at some point you might want to raise your idle speed on the BISS adjustment (on the htrottlebody) to about 1000rpm while your doing this (after the car is warmed up but still in open loop)

 

I'm fairly certain that raising idle speed to 1000rpm or so resolves a majority of these problems anyway since the MAF sensors on our cars like a minimum airflow, if it drops below it due to modifications of the intake (lower engine vaccuum, bigger turbos, less restriction, etc..) it will either disrupt the airflow in the sensor, or drop so low that the car thinks its stalling and it drops back into open loop, goes rich, idles up, then drops back down again..

 

When using larger injectors, they are typically are slower during idle, so when you use injector scaling you are end up pulling out too much fuel and the car will usually end up being too lean to idle. It is best to use a small injector scaling number and then make most of your fuel changes in the fuel map.

The stock car hunting idle is it way for the Long and Short Term Fuel Trims to correct and get close so the car can idle ideally.

Thanks,
Jermaine@turboxs.com