SweetZ..

pretty much what Fred says. If (after the tune) you find you have low idle issues (and your IAC counts are max at 160) and you adjust stop screw so it will idle BUT you now have elevated TPS voltage you will either have to do the "drill" mod or do the "slot the TPS 3 screw holes mod"

With a aftermarket 52mm you should be OK but since you have adjusted the stop screw already you need to get it back to where the IAC & TPS are within spec.

 

I got the engine back together and it started first crank. Sounds real good and it idles high with throttle stop screw backed all the way off. It didn't do that before so it appears that the PCMforLess mail order tune is helping.

I plan to let it get fully warm tonight and try to get the TPS voltage and IAC count in the correct ranges. Will let you know how I make out.

 

Do you know where he set the hot idle RPM?

 

No. I didn't specify a value for hot idle. I let him set it where he recommends. I haven't put my laptop on it yet to see the programmed value. Had a few distractions this week. I hope to have it set by the end of the weekend. Will let you know as soon as do. It is not fun working in this 7 degree temp. My space heater is barely keeping up!

 

I finally got the idle adjusted. The programmed value was 800 rpm. I set the IAC counts to about 28 and the TPS voltage was 0.47VDC. It was very difficult to set the IAC as initially it was too low and when I adjusted the idle stop screw, It shot up to 160. Then when I would adjust again and it would overshoot and go too low again. I was using very small adjustments. The engine temp hovered around 190 - 194 degrees. I was wondering if the thermostat was opening and the slight change in temperature was causing the overshoot. It was difficult but I got it to idle at 800 and the IAC and TPS look good.

Going to test the idle with a cold start tonight to see if works OK but so far it looks good. Will let you know.

 

Unfortunately I had the same problems. I tried cold starting it last night and it wouldn't idle. I did not have a computer attached to monitor the IAC counts but I suspect it was pinned at 160 and I had to keep my foot on the gas to keep it running until it warmed up. Is there anything else I can try or do I need to look at doing the drill mod?

If I do the drill mod, I am afraid it will idle too fast in the summer when it is warm.

 

I think the Edelbrock 52mm TB is the same as the BBK. Check the IAC passages in the throttle body. "Back in the day" the BBK was known for a loud whistle at idle, which could be tracked back to excessive casting flash in the IAC passage. Somethink is limiting the air flow through the IAC system.

 

Sweet..

I have never been in favor of fing with stop screw and then TPS to get aftermarket TB's to work right but some have had success with that method.

The "drill" mod has/does work for me BUT I have a stock but bored to 52 TB which already has the "hole" drilled for IAC. I just had to go 1/64" larger when I went from 350 H/C to a 383 with larger cam (same heads)

you can do two things.

1. put your 48 back on and it should be way better in terms of idle. You "may" have to drill out the 1/8" stock IAC hole 1/64" larger BUT only if IAC counts are high with motor warmed up

2. drill the 52 but first put blades back where they were so TPS volts are .67vdc closed (or close to that) and 4.5vdc full open. drill the 1/8" hole and measure IAC counts. Ideally 30-35 (32) but if still high drill 1/64" more. You should not have to drill any larger. This mod is for TB's that make the motor idle low/stall. Typically H/C motors have this issue with aftermarket TB's

 

There is a picture of the backside of my Edelbrock TB on this site.

http://www.summitracing.com/parts/ed...FW3NOgodKkMAMQ

The Idle Air is isolated from the main plenum and I don't have split BLMs so I don't think I have to install the brass tube. Am I supposed to drill an 1/8" hole (to start) through the TB right through the middle of that hole?

I am not sure how drilling the hole is any different than cracking the butterfly valves with the stop screw and adjusting the TPS voltage. Both ways are letting additional air past the IAC circuit. If I drill this hole, it will idle too high when it is warm outside and I will have no way to stop it.

Is the drill mod right in this situation?

 

How about - put the stocker back on as suggested in the post above. That will tell you if its a problem with the Edelbrock TB. I wouldn't drill any holes until you try that.

 

if you have low idle and your IAC counts are pegged at 160, you need to do either drill or crack blades and f with adjusting the TPS (slot holes) to get those back in spec

I can't see in the Summit pic if there is a hole drilled like stock, I doubt there is.

If it were my car I would/did do the drill mod. when I had a BBK. I now have a stock re-bore to 52 and did "enlarge" the stock hole 1/64" when I went to a larger cam in my 383. That completely resolved the high IAC count issue and idle is perfect

 

SweetZRag, I have the mods shown in my signiture, and have been battling the same problem that you are experiencing. I went with the "cracking the throttle blades open", and re-setting the TPS voltage by "slotting" the TPS mounting screw slots method, because ............ like you (?), I could NOT bear the thought of drilling my brand new 58mm Holley throttle body.

As you suggested, there should be ZERO difference in where that extra idle air, that is already by-passing the idle air circuit, comes from. The "drill mod" was definitely NOT right for me! Also, as you stated above, once a that hole is drilled bigger ...... you can't undo that, like you can with re-adjusting the throttle blades!

 

Sweet....

if you want to try this fix by adjusting blades...

while scaning the car at operating temps for IAC try adjusting the stop screw in small incriments while watching the IAC counts. They should drop and when you get 30-35 at idle that is where you want them.

Now your TPS volts will most likely be off so you need to "slot" the TPS holes to "clock" the TPS back so dcv are back in spec.

or do the drill mod which starts with 1/8" hole and progress from there in 1/64" incriments while watching the IAC counts. Obviously you want to remove TB from car to drill each time. My hole is 11/64" but each motor is diffrent

how does the car idle with the 48?

 

Update - I finally got the car done and am able to test drive it. I finally drilled the 1/8" hole through the TB in line with the small hole in front of the intake. The back of the TB is smooth so no need to install the tube as some have had to do.

After full warm up, it is idling smoothly at 800 RPM as set by the software and the IAC is around 20. TPS voltage is 0.47 and my integrator values are 133(R) & 134(L) (no split). The next day, the car would not high idle and the IAC count is maxed out at 160. The throttle blades are open very slightly using the stop screw. Should I drill the hole 1/64" larger? I am worried about it idling too high in warmer weather.

 

wierd one day IAC was at 20 and the next day max at 160 and low idle.

but if you are still at 160 than you need to enlarge the hole in 1/64" incriments. check each time what IAC counts are. They should absolutely decrease with enlargeing the hole....IIRC my hole with my 383 is 11/64 BUT every motor is diffrent so take baby steps. you don't want to drill to big