I installed an Apexi 3 bar map sensor, selected option 1 in the settings area and now my idle is way too high (1700+). My sensor didn't come with any instructions and I assumed it was just plug and play, but am I missing something? TIA.

 

yeah, assuming everything's hooked up right you're missing a retune.

 

Ok, so how do I regain control over the idle?

 

You are going to need a datalogit for any serious idle tuning because you have to adjust air temperature corrections settings. Idle tuning is a very tedious and time consuming process if you want both the idle speed and the idle AFR to be relatively stable under all driving conditions. Most people just give up and pay somebody to do it, and understandably so.

Once again, assuming everything is hooked up correctly the first thing I would try is restarting the entire idle tuning process. Under the throttle body elbow, recessed between the two studs, is the air adjust screw. Tighten that completely, then back it out 1/4 of a turn (1/2 at most if the idle drops too fast on decel). Reset the Power FC, turn off O2 feedback if you don't have a cat and airpump. Set your idle speeds. I personally use 850, 850 E/L, and 950 A/C , with 1500 for all the F/C (decel fuel cut) settings. Now perform the idle learning procedure outlined in the Apex'i instructions. After that, with the engine completely warmed up, adjust your INJ map so your AFR's are 12.5:1 - 13.0:1 . Every time I adjust the air adjust screw I always redo the idle learning procedure. I'm not sure if that's necessary or not.

One of the biggest issues with idle tuning (with the ISC still functioning) is idle surging due to a lean condition, especially on hot starts. You will need a little more fuel in the higher P rows of your idle area (say N2 P5 needs more fuel than N2 P4) because on hot starts the engine will pull slightly less vacuum and thus fall into a different cell.

Then you will need to adjust your IAT correction table some so that the idle does not lean out under hot starts. I usually richen up the top two cells in INJ vs air temp under settings 2. There are a couple ways of approaching the IAT correction issue though.

If all else fails you can go to manual idle control (set all 3 idle speeds to 0) but in my opinion that is really the route of last resort because you lose the functionality of the ISC valve.

 

Thanks, but if the car idled perfect with the stock MAP sensor, do you think I should start with testing/checking the new map sensor?

 

I don't think you understand. Any time you change the map sensor, the car needs to be retuned if you want it to behave as it did before, even if everything is hooked up right. This is because the PIM values (the primary determinant of engine load) that the PFC sees are now different. Even when you change the calibration of the stock map sensor the car usually needs to be retuned to an extent. It is further compounded by the fact that the factory map sensor calibration is off anyway. If you wanted it to behave exactly as it did before, you would have to come up with a custom MAP sensor calibration so that it read the exact same PIM values as before (mirroring the inaccurate factory calibration of the stock sensor)--which defeats the purpose of an upgraded sensor. There is simply no silver bullet to idle issues in many cases. It's a huge ******* pain in the ***.

 

You could calibrate it. I have the same exact sensor and it always ran "ok." After I calibrated it I noticed a difference... Next chance I get I'll go in my car and get my numbers and send them to you. It can't get anyworse... Right?

 

Thanks, but aren't the calibrations listed as scale/offset in settings 1? If so, I obtained "corrected" scale/offset numbers from Chuck Westbrook's tuning notes.

 

Yes, I used option 1. I guess I didn't really make that clear. The new scale and offset I'm using made a huge difference. What's your full setup? Maybe I'll just send you the map...

 

Power mods:
Brand new 0 mile engine (now has about 5000)
99 spec RZ twins (sequential)
upgraded sequential solenoids (4)
Apexi PFC w/ Datalogit
850cc/1200cc injectors
Walbro 255 (Dale Clark's rewire mod)
Areomotive FPR
Greddy CAI w/ K&N filters
HKS twinpower
HKS downpipe
resonated midpipe
Racing Beat single tip cat-back
XSPOWER SMIC (same as M2)

 

Try scale 45000 and offset 450.