First let me give some info on my setup...

BDC HBP
850,1600cc injectors 40psi base pressure, supra tt fp
jacobs electronics FC1000 amping anFCleading coil, stock trailing coils
single turbo, catless exhaust.
emmisions removed
PFC w/commander
motor has about 1100miles on it
pulls about -12 inHg of vacuum at 1300RPM

Now here is my problem. I set the TPS following the instruction on this forum but the car doesn't want to idle with the tps at the optimal settings,so I have it adjusted toward the high end(though still within spec)

With these settings I can get solid idle between 1300-1500 RPM. And it is set to stay within that range when my A/C is activated(fans) And also under electrical load(lights). Now here is the weird part. As long as the car is not rolling, the idle will hold. But whenever I'm coasting (to a stop for example) the idle will slowly drop until the car stalls. This happens while the clutch is engaged and in gear as well as when the clutch is disengaged and the car in neutral.

The only time the car will hold an idle while coasting is when The TPS is not set within the corract range(on the high side). It doesn't have to be far off butas long as the TPS is set correctly the car will not coast whithout having to keep giving it some gas.

Is it possible that my TPS is the problem even though it isset within spec?Oris there something else I'mmissing?

The car will idle and drive great if the TPS is set wrong, but I was under the impression that it needs to be withing spec for optimum performance and driveability. Can anyone help point me in the right direction?

Thanx
Cyan

 

First about the TPS. The voltage values are for the throttle set normally for a stock engine. A stock engine idles at 720 rpm. That is with the throttle set screw adjusted to open the throttle about 1/4 turn. Adjust it that way then open the throttle as needed for the high idle of your BP engine.

You need to really understand what you are doing with a modified engine as compared to a stock engine!!

Set your FC (fuel cut - really fuel return on points) higher. Your idle is set higher than the FCs are set for stock. You did not say what they are set at. Thus all we can do is ASSUME! Set to at lease 1800 with your BP. It appears you do not know how the PFC works or studied the manual.

 

cewrx7r1- Sorry if I wasn't clear with my setup but I have a 1/2 bridge with the idle set to 1300rpm. No I have not studied the PFC manuals, I have never atempted to tune My PFC. I'm just trying to get a solid starting point so my tuner will not have to worry about setting the car up before he gets started. That being said, with my listed Idle can you give me an idea what my voltage readings need to be from the TPS? I know I'll have to go through the manuals to better understand it but can you give me an idea where I should be?

Thanx for the reply!

 

Set your TPS to stock settings and adjust the idle by the screws on the throttle body. Also set the idle on the Power FC. That is all you have to do for a ported engine in terms of idle.

 

I told you how to set your TPS, and that your FC points need to be raised.
Just experiment using the PFC manual as a guide.

You did not tell us if the ISC/PFC is used to control idle or not.
This type of idle control does not work well with a HBP or BP engine.
I bet that if I saw your PFC map that it I would find problems.
Get yourself a good tuner.

 

if your tuner has base maps that he plans to pre load, he will probably throw everything you are doing right now out the window. Don't mess with a Power FC too much (at least on a heavily modified engine like this) unless you spend a long time learning how it works.

 

When I set it like this the car tries to idle too loe and stalls, even with the screw under the TB all the way open.

Idle is controled with the PFC I'll send you the map when I get a chance tomorrow.

I'm currently using my tuner's base map.

 

Thanx for all the feedback everyone. I'll keep you updated on how this progresses

 

Chuck, You said to set my FCs higher for a BP engine Which I did. But I only set them to 1400. Should I have them at my target idle RPM(1100-1400RPM) for a 1/2 bridge or go ahead and up them to 1800?

The main thing I was confused about was the voltage readings from my TPS. But If I understand your firstpost correctly, I will not be adjusting mine based on what was posted on here and various TPS adjustment sites sence my engine won't be idling anywhere near 720 RPM. And this is why my engine seems to perform best when I adjust The voltage higher than the listed settings?

Thanks again for all your help

 

Q1: You said to set my FCs higher for a BP engine which I did. But I only set them to 1400. Should I have them at my target idle RPM(1100-1400RPM) for a 1/2 bridge or go ahead and up them to 1800?
A1: First off, there are three on them. THE MANUAL tells to set them to at leaste 200 rpm higher than the idle speed. 1400 + 200 = 1600. That is minimum. Why did you set them to 1400, did not read the manual? I set mine higher thus 1800 would be better for yours.

Q2: The main thing I was confused about was the voltage readings from my TPS. But If I understand your firstpost correctly, I will not be adjusting mine based on what was posted on here and various TPS adjustment sites sence my engine won't be idling anywhere near 720 RPM. And this is why my engine seems to perform best when I adjust The voltage higher than the listed settings?
A1: You did not properly read my intructions. (Adjust it that way then open the throttle as needed for the high idle of your BP engine. )
If you set the TPS voltage to the stock value at 1400 rpm idle, it would be less that a stock engine at 1400 rpm idle. That is why I said to open the throttle with the TAS (throttle adjusting screw) 1/4 turn from fully closed throttle and then set the TPS for stock voltage. Then when you open the throttle more to maintane your 1400rpm idle, the TPS voltage will be higher.

If after doing this, the engine does not want to idle, it needs more fuel added.
Large port engines need more fuel and timing to idle smoothly. Using the ISC to try to maintane idle results in very retarded timing which requires more air and fuel just to keep the engine idling. That is while many of us have disengaged the ISC and went to manual idle control. Read about my negative idle timing post.

If you want to really understand the PFC./DL you shoulkd buy my notes package.

 

Thanks for the help and references Chuck! I won't get a chance to mess with it untill tomorrow afternoon but I'll let you know how it goes. Also I sent you a PM about your tuning notes