To idle or not too idle, that is the question
03-11-2019, 10:33 AM
#1
To idle or not too idle, that is the question
Hello, I recently changed my turbo to a K27, changed all vacuum lines, did venturi delete, and changed my ICV (idle control valve), as well as installed LR M-tune (with its MAF).
Overall: engine/boost is great! Beautiful!
Regarding idle, I am having issues. I did the LR idle setting procedure. However, here is the thing: if I short-circuit the B-C pins in the diagnostic port and set the idle speed to around 840 RPM, it means the throttle plate screw is almost closed. Then, when I reactivate the IAV (remove that short-circuiting wire) the AFR gets all screwed-up periodically. With the jump wire there, I can set the idle to 1100 RPM (like now), the FQS setting to 0 (default), and it seems to drive quite well! Idle AFR is 14.X. I can probably reduce the idle to 900 RPM but then cold start might be hard. If I reenable the IAV, idle sometimes has AFR go to 12, sometimes AFR goes to 16 -- when 16ish, then RPMs lower and it wants to die. I suppose too much air. The IAV is the $100 one from 944online....its the aftermarket one they sell and not the $350 Porsche one they also sell. Not sure if that is the issue.
Is it not compatible? any other suggestions?
Overall: engine/boost is great! Beautiful!
Regarding idle, I am having issues. I did the LR idle setting procedure. However, here is the thing: if I short-circuit the B-C pins in the diagnostic port and set the idle speed to around 840 RPM, it means the throttle plate screw is almost closed. Then, when I reactivate the IAV (remove that short-circuiting wire) the AFR gets all screwed-up periodically. With the jump wire there, I can set the idle to 1100 RPM (like now), the FQS setting to 0 (default), and it seems to drive quite well! Idle AFR is 14.X. I can probably reduce the idle to 900 RPM but then cold start might be hard. If I reenable the IAV, idle sometimes has AFR go to 12, sometimes AFR goes to 16 -- when 16ish, then RPMs lower and it wants to die. I suppose too much air. The IAV is the $100 one from 944online....its the aftermarket one they sell and not the $350 Porsche one they also sell. Not sure if that is the issue.
Is it not compatible? any other suggestions?
03-11-2019, 04:37 PM
#2
Drifting
First, how are you reading rpm? If you're using the dash, you're probably about 100-150rpm off; so far, my experiments lead me to believe the dash reads high about that much. Therefore, if you want to get to 840rpm, you should set it so it reads just under 1000rpm. I adjusted my throttle screw so that I get the same steady idle with ICV in or out. Thus, my ICV-out idle should be close to 840--what the ICV is supposed to get it to (at normal oil and coolant temp--something hard to confirm in itself).
I have a brand new Porsche ICV and assuming that the rest of my stuff (all stock) is fine (I believe so), this is what happens at idle with ICV "on": [NOTE: I am measuring the stock 02 sensor here]
In the video, after setting idle I rev it up, hold it a bit, then at the 20s mark release the throttle. It first goes lean then quickly rich, staying rich for a bit then eventually settling back to proper afr.
I have no idea if this lag or time to settle is normal, but if it is, then perhaps that's what you are experiencing. The Lindsey site does suggest that the throttle screw is only about a half-turn from closed. Mine is more like 2.5 turns though
I have a brand new Porsche ICV and assuming that the rest of my stuff (all stock) is fine (I believe so), this is what happens at idle with ICV "on": [NOTE: I am measuring the stock 02 sensor here]
In the video, after setting idle I rev it up, hold it a bit, then at the 20s mark release the throttle. It first goes lean then quickly rich, staying rich for a bit then eventually settling back to proper afr.
I have no idea if this lag or time to settle is normal, but if it is, then perhaps that's what you are experiencing. The Lindsey site does suggest that the throttle screw is only about a half-turn from closed. Mine is more like 2.5 turns though
03-13-2019, 10:37 AM
#3
Thanks great help! I don't have the red-circuit board you have but thanks about the guess of the true RPM.
Here is the next step. I re-set the idle with the ICV short-circuited (meaning B-C in diagnostic port which should make the ICV be in a constant 50% open as I understand). RPM is around 1050 as per my gauge so maybe 900 in reality. Overall drives great once warm. Here is today's sequence:
0. ICV is shorted.
1. started car in 43F weather; it hesitated at first and then went to 2500 RPM on its own and didn't come down to around 1050 until after a few minutes --- some sort of auto warm up?
2. I drove a while, all great.
3. I was about to park car and saw the RPM stuck at 1500. A few pedal presses, and it does not come down -- this was the behavior BEFORE I changed turbo, vacuum lines, ICV, chip, etc which is why I changed the ICV/vacuum lines.
4. Could it be the TPS is bad?
** So the puzzle is this:
A. If physically the throttle was a minimum BUT the TPS registered partial throttle, then I guess the computer would issue MORE fuel which should cause a rich mixture. My AFR was around 15-16 during the aforementioned 1500 RPM (when at 1050 its 14.5-15).
B. If physically the throttle was a minimum BUT the TPS registered zero throttle, then I guess the computer should issue the standard idle amount of fuel and the RPM should be 1050 (btw, my speed and ref sensors are both newish).
Thus neither A nor B seem to be occuring at that instant, thus TPS is not bad (it was calibrated as per LR website to "click" upon a slight motion).
So, if TPS is good, ICV is out of the equation, how can idle change from 1050 to 1500? I'm pretty sure no vacuum/boost leaks exist, as per other testing. Also, it does idle at 1050 sometimes/usually.
Thoughts?
Here is the next step. I re-set the idle with the ICV short-circuited (meaning B-C in diagnostic port which should make the ICV be in a constant 50% open as I understand). RPM is around 1050 as per my gauge so maybe 900 in reality. Overall drives great once warm. Here is today's sequence:
0. ICV is shorted.
1. started car in 43F weather; it hesitated at first and then went to 2500 RPM on its own and didn't come down to around 1050 until after a few minutes --- some sort of auto warm up?
2. I drove a while, all great.
3. I was about to park car and saw the RPM stuck at 1500. A few pedal presses, and it does not come down -- this was the behavior BEFORE I changed turbo, vacuum lines, ICV, chip, etc which is why I changed the ICV/vacuum lines.
4. Could it be the TPS is bad?
** So the puzzle is this:
A. If physically the throttle was a minimum BUT the TPS registered partial throttle, then I guess the computer would issue MORE fuel which should cause a rich mixture. My AFR was around 15-16 during the aforementioned 1500 RPM (when at 1050 its 14.5-15).
B. If physically the throttle was a minimum BUT the TPS registered zero throttle, then I guess the computer should issue the standard idle amount of fuel and the RPM should be 1050 (btw, my speed and ref sensors are both newish).
Thus neither A nor B seem to be occuring at that instant, thus TPS is not bad (it was calibrated as per LR website to "click" upon a slight motion).
So, if TPS is good, ICV is out of the equation, how can idle change from 1050 to 1500? I'm pretty sure no vacuum/boost leaks exist, as per other testing. Also, it does idle at 1050 sometimes/usually.
Thoughts?
03-13-2019, 11:50 AM
#4
Drifting
The cold-start higher-rpm is normal. Have you tested or changed the coolant sensor in the head or its wiring? If not, do that next. It may be wonky and intermittently reporting cold instead of warm.