AndrewPearce11

Injuneer

In the scanner's view data function, have you displayed the full list of the long PID names (option for long name needs to be turned on in setup) of all the PID'S the scanner is capable of displaying, for the specific PCM it is connected to?

AndrewPearce11

Injuneer

I don't know the details of that specific scanner. But looking ar the instruction manual, page 4-19 indicates there is a function “View Entire List” that will show you what PID’s are supported for your specific vehicle. Maybe that's the list you posted.... I don't know. Or perhaps that is the default list and there are more functions in the “View Entire List" function.

AndrewPearce11

Injuneer

There is a list of all the PID's in Appendix A of the manual and I don’t see IAC counts or TPS volts.

I don’t have much hands on experience w/ the LS1. I do have a 2000 factory service manual. Let me take a quick look at that. If it was an LT1 I could tell you how to get it close without a scanner. On the other hand, there is free LT1 scanning software that will show IAC and TPS.

AndrewPearce11

Injuneer

The factory manual indicates the TPS volts need to be between 0.40 - 0.90 volts. They show the IAC counts as "variable". The control system looks similar to the LT1. In the LT1 the range of IAC counts is 0 - 256, but the upper limit in the program seems to be 160 counts.

Typically you extend the throttle stop screw out until the RPM exceeds the target idle RPM. That takes RPM control away from the IAC motor. Then slowly back the screw out until the idle RPM (fully warmed up engine) matches the idle RPM target programmed in the PCM. At that point you will typically be at 0 IAC counts. For the LT1, target idle speed with the M6 is 800 RPM, and with the A4 in neutral, 650 RPM. A custom tune may have altered these.

After you get the RPM right, you check the IAC counts. Back the screw out slowly until the IAC counts are in the range of 20-40 counts. Then check the TPS volts to make sure they are within the specified limit, which a ~0.30 - 0.90 volts for the LT1, and apparently 0.40 - 0.90 volts for the LS1.

A dealer TECH 2 (~$4,200) will read the TPS volts and IAC counts. There are Chinese clones of the TECH 2 (~$280) that actually work fairly well. Member here, GaryDoug who wrote Scan9495 software for the LT1 has tested a Chinese clone. The TECH 2 is made by Bosch, who also owns OTC products.

Your best bet may be software. Take a look at EFI Live. I do not know the specific compatibility with the 2000 LS1, but EFI Live was originally designed specifically for the LS1.

AndrewPearce11

Thank you for your information. I decided to go ahead and try to adjust the Throttle stop screw in order to get the car to idle correctly. I ended up going through the process of turning the screw 1/4 of a turn each time and then resetting the TPS sensor. I did this many times and still could not get the darn thing to idle. I Even bottomed out the Screw. I did the process by watching the TPS % on my scan tool and adjusting the screw. I saw that some people drill larger bleeder holes into the blade but I am wanting to avoid that method if possible. I have seen that I can check the TPS volts but sticking a small pin into the middle red wire and sticking a pin into the bottom black wire and then using a volt meter to check the volts. I am wondering if there is some alternate way to check the IAC counts?

It idles fine when it is cold, and if I let it, It would sit and Idle for as long as I want. However, The moment that I touch the Throttle It wont Idle. I Have to keep my foot on the Throttle to keep it from wanting to die. I don't think the issues is a vacuum leak because it will idle fine when it starts cold.

I have a friend that owns a high dollar scan tool that I am going to take it too soon and see the IAC numbers. However, If I have moved the set screw all the down (in 1/4 turn increments and resetting the TPS each time) and it still did not Idle, is there possibly A different problem?

I have a mail order tune from FROST and He gave me a paper that told me that the blade would have to be adjusted via the throttle body screw in order to get it to idle correctly.

Thanks for the help. I just want to DRIVE THIS THING!!!

Injuneer

What exactly happens when you touch the throttle and it “won’t idle"? Just seems to load up with fuel? .... seems to die from lack of air? ... does the idle cycle up and down?

You can measure the TPS volts, because it’s a sensor and is sending a voltage signal to the PCM. But the IAC “counts” are instructions being sent from the PCM to the IAC motor, which is an actuator. You have to read counts from the PCM via a scanner. And that raises another issue. When you read the counts from the PCM there is no guarantee the IAC motor is reacting by moving the pintle to the correct position, other than the fact that the idle RPM is correct. There are codes that set if the actual RPM deviates from the target RPM.

Is the scanner showing any codes?

I don’t see your location shown? Are you located where there is a cold climate? When you start the engine, the PCM looks at the coolant temp and elevates the cold start idle, and richens the A/F ratio based on the temp. In exceptionally cold weather, target idle speed can exceed 1,000 RPM. You need too set the TPS/IAC/RPM with the engine fully warmed up.

You indicate you have tried with the “screw bottomed out”. Do you mean the throttle blades are fully closed? If so, that may reduce air flow to the point the IAC counts are raised as high as they can possibly go. The IAC pintle can't open up further to let more air in.

When you were backing the screw out (closing the blades) did the RPM drop briefly and then quickly pull back up as the IAC responded?

Out of curiosity, what is the TPS voltage he told you to hold? Did he tell you what the programmed target idle speed should be, engine fully warmed up?

What changes did you make to the stock LS1 that necessitated the tune? Any chance there is large cam or an aftermarket throttle body involved?

AndrewPearce11

It is a stock Throttle body. The LS1 has a BTR stage 3 cam kit with long tube Headers. It has a AC delete. EGR delete and a cold air intake. I have a 2800 stall in the car now but I am planning on upgrading it to a 3600 stall here soon. I went ahead and told Frost to tune it as if it had a 3600 stall in it. Could that possibly be the problem? It seems to me that the stall would not matter if I am just trying to get the car to idle and not taking it out of park. (correct me if I am wrong)

When I hit the Gas it revs up like it should but then stalls as the RPMs come back down. After I do that the car will not idle properly at all. I have to hold the throttle to get it to stay running. Even if I turn the car off then back on it still does this. The only way it will go back to idle is if I let it completely cool down.

I am in the Martinsville Indiana area so it is a bit chilly here now. I did let the car warm up to operating temperature and kept it at about 180*

When I was saying the screw was "bottoming out" I meant that I had opened the throttle blade as wide as the screw would push it. I then backed the screw back out(closing the blades) and started the process again. I did not touch the screw while the car was running because I thought that I had to reset the TPS sensor each time I moved the screw which requires turning the car off.

I am going to contact Frost and see what he has to say. I can almost guarantee that He will say that I need to change the torque converter before I try to get it to Idle. I am going to try that and see if that works. FTI told me that they would restall my torque converter for Free.

AndrewPearce11

I heard back from Frost. He told me that there is no point in setting up the Throttle body before getting the correct stall installed. He said that the weight of the stall can effect the way that it idles.

Here is what he said.

"Another item that can affect idle like this are cylinder misfires (the car will reek of fuel when running). With an aftermarket cam, misfire detection must be shutoff. You must be able to diag something like this in another fashion vs. waiting for a code/count if it's a an issue. The tuning does take into the account the lack of inertia held in a smaller stall relative to the large heavy OEM unit. The factory idle control relies on spinning inertia of FW/converter on top of other factors. The aftermarket units will cause RPMs to drop like a rock, so there there is airflow and spark that chases throttle down. If the RPMs are too high when adaptive idle resumes, it will cause a large dip or stall (it needs to start updating at 1K ish RPMs.... if the engine is slower revving down and idle adaptive starts up early, it will cause a negative airflow value that can make it stall)"

I will be taking out the stall here soon and putting in the 3600 stall and see if that helps the situation. I will also be checking all the plugs and wires to see if possibly I have misfire. I will do the Throttle body set up again after the new stall in put in. I'll update you guys on the situation.

Injuneer

I have to keep in mind that the LS1 PCM is light years ahead of the LT1. Appears it’s a lot more sophisticated with regard to idle control. Frost sounds like he's on top of it.

Wish we had more members here’s with LS1 experience.