Ok My problem is that my car will not idle any longer. It has been idling ok at about 1600 RPM but would not any lower without falling on its face and dying. Now It simply will not idle in any fashion and when driving it does fine on acceleration but will die when you let off the accelerator. I can hear it when downshifting the tone changes until you push on the gas a bit then it cracks back to life.

This is a 2nd gen with Half bridge motor, Tso4 turbine, 550-1600 injectors. No BACV or dashpots. Motor is bare bones track only. I have the idle control turned off on the PFC and the idle values set to 0. I have tried everything I can think of. I am suspecting the TPS but then again it should attempt to idle even if it is bad right? I did swap in another one I had lying around and the problem did not really change. I do not have any vac leaks that I can find and this car is MAP sensor so it should idle up and not just die. All voltages for sensors etc are withing spec.

Somebody help me.

 

Have you looked at your AFRs? If an injector is slightly sticking open, it might not idle due to being too rich but will run OK with more load/air flow.
How does it start cold and hot? This should help indicate something.

 

pressure test for vacuum/boost leaks. i've discussed this in some 2nd gen section threads, do a search

check that AFR's aren't too lean

open the throttle plates to raise the idle air by using the primary throttle plate stop screw. Given that you've removed all the idle related stuff, you'll probably need to open the throttle plates enough so that it will idle higher. since it is a half bridge it will get a weak vacuum signal at low rpms. try to get it to idle around 1200 maybe.

 

Ok thanks for the information. I will do a pressure test on it today. over the last days I have gotten it to idle at about 2k rpm and it revs fine and stays alive coming online for "idle" at 2k every time.

When trying to adjust my TPS if I adjust the voltage below 2.35v the car will instantly die..... Wierd~ The car does run fine and I supposed to drive in D1 Chicago this weekend. Im almost afraid to mess with it right now .

As far as AFR's when it was running at around 1500rpm I was seeing 11 afrs and leaning it out caused the idle speed to increase....maybe the bridge causes unreliable afr reading at idle?

 

s4 TPS right? the s4 TPS signal (narrow range only) should be spliced into both FD TPS pins for both narrow and full range



verify you have zero vacuum leaks, then adjust the throttle stop screw carefully and see how far you can drop the idle down, noticing changes in the vacuum reading as the throttle plates close.

 

Oh sorry not S4 mine is S5 and I am using the AP engineering PFC.

I checked for Vac leaks today and cannot find anything. I have the boost controller and map sensor refrencing from the small nipple on the UIM, Wastegate is refr. from boost piping. Fuel Pressure is ref. from nipple on back of UIM and BOV ref. from front of UIM.

Thinking it could be a wiring issue since this car has had many. I rewired the entire harness with the exception of the shielded wires which I didn't want to tear into. everything did Ohm out however.

I really appreciate all your help. I am gonna go ahead and run it the way it is in Chicago and deal with it when its over and I have time to mess with it.

 

it sounds like you just need to open the throttle plates more as I said. you have a bridge port and no idle control system (BAC) so that's your only real option.

 

The BP motors pull far less vacuum at idle, which means you need to modify the area of the map that it is actually using to reflect the correct timing and fuel correction that the car will need to idle correctly. Set you idle values back up to an actual number, having them at 0 is only useful on some cars, I find having a number in there works far better, set it at 1100 or so to start.

 

OK. I will try to adjust the map and set the idle values. This is my first BP so there is a learning curve for me. If the car makes it through this weekend i will spend some alone time with the maps.

 

on the commander or datalogit monitor window, what is your timing at idle (actual observed values, not what's in the map)? leading and trailing