As above. I can not do the minimum air/IAC procedure because the engine stalls out. I have turned the TB screw 3 full turns out and that still is not enough air for the engine to idle without massive air from the IAC valve.

What the LS1 guys do is to drill the TB plate with a hole.

 

I have, but if I've been reading right the car has other issues? Might want to address those first.

If you do get crazy and drill anyway, start small. It does not take much at all, if you go much more than 1/16" in each plate you might go too far and its not easy to put that stuff back in

Well... just read your other post. I wouldnt advise that much so soon, but.. if its workin, more power to ya.

 

How big of a cam are you running???

I got a 227/233 on a 112 and mine turned more than enough to idle at 850....

 

The cam is 224/230 @ .050 lift and 114* LSA. It should be fairly ECM friendly. I have had problems with vacuum leaks, but I think that I have located & elimenated them all.

MadMax, I have drilled both TB plates with an 1/8" hole. The IAC count before drilling was something like100 to 110 while driving around and 160 when I stop. This was with the TB adjustment screw out 2 to 2 1/2 turns. Now its at 85 driving around, but still nearly hits 160 (maybe about 140 to 150) when I stop in gear.

 

Do you have a custom prom? That is where the idle rpm is adjusted at anyway.

 

John, yes, I 'burn' my own Eproms. I have bumped up the idle RPM to 850 RPM (at fully warmed up temps), however, the IAC could not react fast enough for the engine. When I would come to a stop, the RPM would nose dive to 400 RPM, and then it would sputter and die.. Sometimes I could catch it with a stab at the throotle, but I dont want to do that forever. The car has to come to a quick stop without stalling out. I notice with my scanner that the IAC would hit 160, so it was maxed out and still could not feed enough air to the engine at closed throotle.

 

I have the same cam and didnt have that much of a problem.

Check the IAC housing, make sure its tight and not leaking. Silly me, once I thought it was all tightened up and it was only the screws that were tight, the housing was loose. The alignment pin fooled me into thinking it was actually being held on there right.

 

Do you have the minimum air screw cranked all the way (as in, are the throttle blades being held open as much as possible by the screw adjuster)?

 

And are the TB and IAC whistle-clean? The ECM can throw all the IAC pulses it wants at the stepper motor, but if the stepper is dirty/sticky, the air passages are dirty, spring is too strong, or the pintle head has fallen off, it just won't matter. A correctly functioning IAC and ECM can deliver enough idle air to hold a stock 350 TPI at 2,200 RPM if everything is clean - no problem whatsoever. I have doubts that a mild cam like that would require any more than that.

Drilling the throttle plates is a Ford procedure, and is relatively permanent.

 

The IAC is clean and is operating A OK. The root to my problem actually goes to not setting the correct static timing. But I still would have needed one small hole in the TB so as not to have the idle screw turned out 3 to 4 turns. Dummy me, I totally forgot to disconnect the EST wire when setting to static timing, just a total and complete brain fart on my part. I was actually at 5 degrees RETARDED static. I thought that I was at 13 degrees advanced.

One 3/32 hole is good with this size engine and cam. As things are now, the IAC is at about 10 counts with the engine idleing at 800 to 850RPM with the idle screw NOT out at all. I will put a screw in one hole and seal the threads with red lock tight. It better not come loose!!!!

BTW: With 10 degrees static timing (instead of -5), the engine runs cooler. AND has come alive like you cant believe. The throotle response is awesome. So it pays to know what you are doing, unlike myself.

To all you guys who posted here, thank you very much for your help.

 

You do realize that adjusting the minimum air screw IS a good idea and how most people get enough air into modified engines for them to idle properly, right? You just have to reset the TPS sensor when you are done setting the minimum air screw. I have mine opened up just about all the way on my 58mm TB to get my IAC counts down around 15 or so and then I have the requisite changes to the TPS to get it set right for idle and WOT.

But I am sure that some setups do require a hole or two in the TB plates to get them to idle properly.

 

Matt,

Appearantly, I did not have to drill the TB plates. So, I made a mistake. It was the failure to set the static timing correctly, that led me to drill the plates. Now, the idle screw is all the way in (not holding the plate open at all) and the idle RPM is about 800RPM with an IAC around 10. I set the static timing to 10 degrees. Before, it was actually at -5 degrees.

And, yes, once the static timing is set correctly and the idle RPM is good, and the minimum air, we should then re-adjust the TPS. I prefer to run the TPS at 0.62 to 0.64V. Actually, resetting the TPS at closed throotle (at idle) is important for improved drivibility and throotle response.

 

Well I am asking because it just seems like from what you are typing here that you are attempting to avoid adjusting the minimum air setting any higher than stock (or at all?) at all costs when it is actually the proper way to get enough air into a modified engine to idle smooth and not require excessive IAC counts to achieve that desired idle.

It really shouldn't matter at all that you did drill holes though. And it sounds like you have it all worked out with an 800 RPM idle and the IAC at 10 counts (now that the timing is also dialed in).

 

The engine idles very smooth now, I'm quiet satisfied with the idle. As stated above, I was fooled into drilling the TB plates, because I did not disconnect the EST wire when setting the static timing (well brain fade here). But, I do have 395 cubes now, not 350.

You are right in that I did not want to turn the idle screw out an excessive amount. My goal was to have it out the same as with the 350, but I messed up on this due to the static timing. I would prefer to have the idle screw out about 1-1/2 turns, IAC counts at 25, with idle RPM of 800. But, I am at no turns out, IAC at 10, and 800RPM for idle.

I will probably use a small bolt & nut with tons of lock-tite to fill one of the holes. Right now, I am burning Eproms for the engine. I'm slowly getting close to a good tune.

 

Why not just leave the holes open? The nut/screw will impeded air flow or worse yet come off and get sucked into the eng.