Thats a large cam on a stock block, the same size I have in my stroker. Hmmmmm.

 

yes sir it is.....lets hope the block holds for a little while.

 

I was using that same cam with my stock TB in my 383. (Just installed a 58mm TB) I had no idle issues at all. I am thinking you are having problems some where else. I found that bad O2 sensors can cause a hell of a pile of idle problems!!

 

My IAC value was well above 100 most of the time...too rich? A/F ratio guage say's I'm well on the rich side...

 

To log with Datamaster:

go to FILE/record ALDL data
select com port under setup
in the Serial Data Aquisition window, select FILE/open
name a new file and click open
back to the Serial Data Aquisition window and click start when ready to record.

Datamaster is easier to read.


On a stock car idle count are in the 20-40 range. When you add a cam the counts will normally go up. Have you tried cracking the throttle blades just a little with the stop screw? With the cam you have, you may need to. That will allow the IAC to have a better range of control (bring the counts down).

 

IF (and only if) more air at idle is what you really need, it would be better to use a drill and open up that small hole in the t.b. where the IAC pulls air in. (like what turboZ said) Drilling holes in the t.b. blades or adjusting the stop screw (good for testing only) will allow more air into the main intake plenum, which could result in split BLM's. There is actually a whole separate plenum within the intake (just below the main plenum) just for IAC air. It has very small holes that feed into each intake runner allowing for more even ditribution of air at idle.

 

My guess is that the IAC bypass hole in the TB needs to be enlarged because idle airflow demands at 1200 are a lot higher than at the stock 550 rpm.

Thus the IAC motor is opening way up to get the required amount of air in there.

I think the stock hole measures 5/64 or slightly bigger. I'd go up to 11/64th and log the change in IAC counts, then go up the next step bigger, adn so on until the IAC counts get down in the 30-40 range.

I would resist craking the TB blades at idle because that is likely to cause a BLM/Fuel trim split at idle..you want as much air going through the idle circuit passages in the intake manifold as possible.

 

I'll run Datamaster here in just a bit, and no, I havent tried the stoop screw yet...will give that a try also.

Appreciate the quick and great responses!!

 

Adjusting the stop screw was meant for a method to test whether more air would help solve the situation. If it were me, I would try this for a test before boring irreversible holes in the TB. Opening the IAC passage will probably be what you will want to utlimately do and it will avoid the split BLMs that were mentioned.

 

Okay, in my original post, I uploaded 2 .uni files from DataMaster. Hopefully these will be adequate.

Also, I didnt actually ADJUST the stop screw, I just chocked the wheels on the car and put it in drive (with E brake on) and slowly pulled the throttle open. It smoothed out a little bit, but wanted to roll before it was ideal. If I would've turned the stop screw, it would've been about 3 turns..same distance.

 

ttt

Been reading on LT1 edit and viewing the Datamaster files, trying to get smart.

I'm curious though, my long term fuel trims occasionally go over 128, but they arent even..meaning right side may be at 134 when left side is at 125...is that normal, also, anything above 128 is becoming too lean?