F-Body Tuning Issues

[Schwanke Engines]

I have been struggling with 2 F-body cars for the past 2 weeks now. One that should be the easiest is a 2000 Pontiac Trans Am with a Stock LS1 and a cam change it has a 230/240 Duration .592/.605 Lift on a 113 Lobe center, all SAS and EGR was removed and Long tube Headers were installed with out Cats the rear O2's were removed. At first I was having troubles getting the car to Idle up to desired Idle on startup. Now for the last week I have been fighting Issues with the IAC and TPS basically after moving the car in gear and stepping on the throttle at all the Idle speed picks up and sticks at 1800-2000 RPM's until the VSS reads 0 MPH. Then It slowly comes down to Idle but the second you pickup the throttle and take off in gear it does the same thing and sits at 2000 RPM's. When this is all happening and you push the clutch in the TPS is at 0%.

I had this particular car perfect the other day It came down to Idle 1-2 Seconds after popping it into Neutral or pressing in the clutch. Then out of nowhere after 3-4 Drives it goes back to the same thing of Holding the Idle up to 2000 RPM's even If you dont throttle it up to that point It will raise up to it.

The second car is a 1998 Camaro with a 99+ PCM swapped into it, this engine was not build by us, it's a 408 Stroker 6.0L with PRC Cathedral Heads on it and a FAST 102 Intake 248/254 Duration cam
615/622 Lift on a 113 cam installed. The engine starts and Idles perfectly It revs up and comes down to Idle before you move it, but again the second you move it in gear it holds the Idle up but on this car it is much worse and pulls it up to 3000 RPM's.

I have tried everything I can think of, I figured it was an Closed loop issue at first, and on the Camaro the O2's were not working so I shut them off and it is running Open loop full time same Issue. Bot cars will work perfectly if you unplug the VSS and drive them the Idle comes down right away and is excellent. If you also unplug the IAC after startup both cars run perfect. So this is where I have the Issue obviously I need the IAC for startup and the VSS for the speedo. Is there anything anyone has for Ideas these cars? Ill attach TUnes and Logs for both cars.

[joecar]

I take it you eliminated any airleaks, especially on the 1998/FAST...

[Schwanke Engines]

I take it you eliminated any airleaks, especially on the 1998/FAST...

Yes, no air leaks. As I stated in the OP, it works perfectly until you move either of the cars ahead in gear 1 foot then they want to idle up and stay there until you come to a complete stop. Basically something is causing the IAC to stay open too long, and the only thing I have found is the VSS, if unplugged both cars run perfectly.

[BLK02WS6]

On the first one - your high octane table is extremely high in the idle region. If you look at the log, when you touch the throttle, it is going from the base table and into the high octane table (look at what timing is doing). I see you have the threshold raised way up, but that doesn't seem to be keeping it in the base table...

[BLK02WS6]

Finally got a chance to look at the second one - I see you have disabled many (pretty much all) of the factory settings (throttle cracker, spark smoothing, etc). Not sure why you would do that. You should be able to utilize the stock tables and manipulate their values to get the idle you want - both sitting still and rolling. Based on what you have, it is hard to find exactly what is doing it. Personally, I start with stock tables and add air where needed using the desired airflow, throttle cracker, and throttle follower tables. I know that wasn't much help, but I sifted through many of your tables trying to find it, and so far, haven't...

[BLK02WS6]

Also, you have to remember (based on your statement about both running perfect when VSS is unplugged) more than just IAC works off of vehicle speed...

[joecar]

It might be good to set everything back to stock and only modify the necessary tables, just as Bret said.

[Schwanke Engines]

I was able to get the 2000 Trans Am done on Saturday, and it works perfectly. Changed the High Octane table helped some, but apparently someone had drilled the Hole in the throttle body to 1/4" and that was causing all sorts of issues with the IAC. The biggest problem with both cars is that Someone else worked on them before I got to them. Both had been tuned previously, so I am basically trying to fix someone elses mess. The 98 Camaro with the 408 was tuned prior to us tuning it last year. And I have no way of getting the stock Cal back.

[joecar]

Glad you found it.

[Schwanke Engines]

I am still struggling with the 98 Camaro with the 408, I found the 102 MM throttle body on it has about a .010" air gap around the entire edge of the throttle plate and someone still had a 3/16" hole in it. I have since plugged the hole and gotten some direction, but still cannot get it to come down in RPM's after I have moved.