I seem to have this high idle situation, where the car will idle @ 2k or higher while at a stop or cruising in netural with foot off the gas pedal it will slowly creep back down to 1000 rpms where it's set at but not right away it takes a minute or two. Now my question is Can the drill mod cause this code???

I found that my car has 2- 1/4 inch holes drilled in the throttle blades.. I was told this is done to help a car idle when it has a big cam but can this cause enough air to come through those holes and create a high idle because it's not going through the IAC valve like it should be?

Please someone help me with this I had a speed shop Perform a dyno tune and im kinda upset because of the fact that my $400 dollar tb has to holes in it that may be causeing this code and my high idle problem, if it's possible i want them to take care of the probelm they caused. There are no intake leaks, no tears or rips in the intake elbow this is the only thing i can think of that could cause this.

 

yes the holes can be your problem.

I drilled 1/8th in holes in mine when I had the SC and a big cam to keep it from surging. After I took the blower off and got a good tuning suite it was no longer needed

 

yup you found it

Think about it, those holes are the equivilant to you having the gas pedal pushed down a little bit.

3800stall TC??? Wow you must turn some RPM there.

 

Me? Only what the stock PCM will give me...7,200 or so..

 

Well for all that read this is it necessary for those running the GM847 Cam to have holes drilled in your tb to help it idle in cold start conditions or help idle peroid?

I've done some data logging with the holes open heres what i found while idling in closed loop with coolant temp @ 180 degrees

IAC position 0
IAC memory 10
Desired idle 900 Rpm
Current Idle 1163-1230 Rpms (jumps around because of the cam)
Tps Volts 0.69
Tps % 0

Holes blocked off

IAC postion 67
IAC memory 41
Desired idle 900 Rpm
Current Idle 863-913 Rpms (jumps around also but it alot closer to desired then before)
Tps volts 0.69
Tps % 0

Now i talked to the shop and basically replacing my throttle body is out of the question because the holes help with "start up" Now i know im not crazy but i will ask is there anything else that could cause this issue besides those holes?

 

That's awesome.

 

Have you checked for vacum leaks, maybe the EGR. I have a jumpy idle at the moment and found my EGR tube to be leaking, causing a vacum leak and making my idle jumpy.

 

Checked for vacuum leaks nothing found. The car doesnt have Egr or A.I.R I also checked for a proper functioning IAC Valve and it seems to be withing spec and working correctly.

 

so, who put those large holes there? If it was the shop they need to replace your TB. if they won't, sounds like small claims court to me.

-Ryan

 

Pm sent! I don't want to publicly bash a shop, there willing to take a look at the car and data but have already said that they will not replace the tb because they do it to all LT1's and theres nothing wrong with that mod on "large cam LT1's"

 

I just got my 97 back from the shop from being dyno tuned, the TPS is sitting at .73 at 0%. The car doesn't idle worth a darn, and it doesn't seem that the shift points are even set. When I asked the shop about the idle, they said to crack the throttle stop open a little more. The issue with that is that the TPS voltage goes up and messes with the trans. shift points even more. They said the only other thing to do was to drill holes in the throttle body blades, but I don't want to do that either really.

 

there has been NO reason to drill holes in LTx TB blade since 99 when LT1 edit came out. NONE at all!

I ran an 847 cam on my 350 LT1 with NO issues after we tunned it.

Drilling the holes is an Ignorant mistake at best these days

Find a better tuner I don't do long distance but some of the people here do

Ion and Brian come to mind

 

Ion has done tunes for me & my brother in the past and is a great guy.. but i thought the dyno tuning i was paying for would of paid off better then a mail order.

 

Depends on who is doing it

Good luck man!