Billiumss

iTrader: (11)

I have been seeing this on a lot of cars that have a somewhat bigger cam, bigger than a TR 224.

When you are coming to a stop and going about 20 MPH or less or so, you push the clutch pedal in and go in neutrel and 70% of the time the rpm's will go below the set idle by 200-300 rpm's then come back up to the set idle.

The cars I see don't stall or anything just that it shouldn't do that.

I tried messing with the Throttle Follower tables and didn't have any luck.

I then tried the Throttle Cracker table and that helps some but it still does it. I tried 10% and the idle took a while to come down but it didn't go below the set idle rpm.

So what do you guys do to make the rpms return to idle like a stock car does. It has to be done cause the IAC controls it.

This should just be a simple fix with those 2 tables right?

Bill

1fastWS6

iTrader: (3)

Use the IAC in gear and RAF tables. I think my RAF table is at 28 across the board. Then I start raising the IAC in Gear values until the idle starts to hang, then back them off a bit.

Cal

iTrader: (1)

I think the problem is the stock IAC can't open wide enough to let in enough air for a big cam under the conditions you describe. My car does that a little bit even with only a TR224. I've logged data and found that the IAC is maxed out. You can drill an even bigger hole in the TB plate (you should have a bigger hole than stock already,) but then you have too much air under other conditions. I've tried this and found that the IAC closes all the way in some situations. My theory is the IAC needs to have more range than it does to support big a cam properly.

Billiumss

iTrader: (11)

Thanks for the tips guys.

Right now my IAC is at about 35-40 at idle and it might dip to 25 at times. I do have the hole drilled out one size larger too. A zero value is fully closed, then that means my IAC is not maxed out yet.

I onced checked out a car that had a high idle all the time after a ported TB. The IAc count was at "zero" all the time and the idle was at about 1000-1100 RPMs. We pulled the TB off and it was ported too good around the TB blade, you could see a lot of light around the blade when held up to a light.

So, adust the "Throttle Follower Airflow Decay in gear" right? Set the lower values to 28? What is the RAF table?

1fastWS6

iTrader: (3)

No, not the decay. Actually its the IAC Park Position not RAF. My bad.

Billiumss

iTrader: (11)

Nope didn't help.........

I did lower the decay in the follower and cracker tables by 5% and it seemed to help some but it still does it.

Is there a long learning curve for the PCM for these type of changes?

1fastWS6, do you have a edit file I could look at?

Bill

P Mack

iTrader: (6)

You might wanna try opening your throttle blade up a little more with the set screw and get your IAC's down below 30. It's weird, some cars will surge with IAC's of 35, others will "hang". So getting your IAC's lower is worth a shot I think.