Why does this engine want to idle at 1500RPM

[sparkinak]

Stock 6.0 Block
Brian T Stage 4 Cam With upgraded springs and trunions
GMPP CNC ported LS3 Heads
Stock LS3 Intake and Injectors 42lb
100mm Throttle Body DBC
Built 4l60e with 3900 Stall converter:Eyecrazy::Eyecrazy::Eyecrazy::Eyecrazy:

I have updated the Injector Flow Rate, and I have played with all the tables I could think of. ECM was from a 5.3 and I have tried to modify accordingly but for the life of me I can not figure out why the heck this thing wants to ideal at 1500rpm and be a pain in the booty to start. I am ok if someone even says hey dumb a$$ go look at this table or these tables and figure it out. I have been dinking with this for few weeks now and just looking for ideas on where to look for get it running close to normal so I can do the auto tune setup with the wideband.

Kevin

19935

[joecar]

Hi Kevin, an airleak would cause the idle rpm to go high like that.

[sparkinak]

That was my first thought, however it did this with my stock parts. 6.0 stock heads and cam, ls1 intake and injectors...
I have literally poured brakeclean everywhere trying to find airleak. Not that it probly matters but watching my afr its 14.x to 19.x

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[joecar]

What PCV plumbing do you have...?

[sparkinak]

Like old school setup. Filter at the valve cover and capped off on the intake manifold.

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[sparkinak]

Looked at it again just to make sure.
Drivers side has the valve and a mini filter on it. Passenger side goes out of valve cover to throttle body. Nothing in valley cover.

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[MobileProg]

What valley cover?

[1FastBrick]

What brand of 100MM DBC? is there an adapter plate on it?

Are you sure it's making a good seal with the LS3 intake? Those intakes were DBW from the factory so I am curious if there is a mismatch in this area allowing air in?

I know the FAST intake had this issue with there manifolds with certain brands of Throttle bodies.

[sparkinak]

I lied, holley 90mm and it bolts right up to the stock ls3 intake.

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[sparkinak]

The only problem id have with the bad fit to ls3 is i had this same problem before with all ls1 stuff but same tb.

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[sparkinak]

Bump, for other ideas, rude comments, name calling, pictures of stuff?

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[LastCall]

Can you post a log of the IAC counts and short and long term idle trims at idle? Is the set screw on the TB cracking the blade open too much?

[sparkinak]

I didnt log Iac but can say its adding fuel for the long term as its in the positive, which im assuming would suggest vacuum leak. Im gonna try a different approach to the pcv just to make sure 100% thats not an issue. tps shows its at .4% or .04% off top of my head. I will post the last log i took here shortly.

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[LastCall]

I didnt log Iac but can say its adding fuel for the long term as its in the positive, which im assuming would suggest vacuum leak. Im gonna try a different approach to the pcv just to make sure 100% thats not an issue. tps shows its at .4% or .04% off top of my head. I will post the last log i took here shortly.

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I was referring to the idle trims, not fuel, those PIDs are in the idle folder/sub-selection. The TPS sensor can be reset to read 0%, so it may be worth looking into. What are your desired air flow values at operating temp? If your IAC counts and/or idle trims are negative, I would back out the set screw on the throttle body. Ideal is 60-80 counts at hot idle.

[sparkinak]

19939

I know that doesn't have probly any helpful info but thats what I was looking at. I'll see if I can get into the shop tomorrow and take a log of those pids.
Thank you for help.

[LastCall]

You get a chance to log those PIDs?

[sparkinak]

You get a chance to log those PIDs?
My 10k dollar tranny with 38k miles just took a dump. Nursing it home then going to go do log. Will have them shortly

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[sparkinak]

19951


Ok here is a log file with a bunch of IAC stuff. It looks like max was 140, 39...

[LastCall]

I'll look at when I get home. Can you attach your current tune?

[sparkinak]

I'll look at when I get home. Can you attach your current tune?
Yeppers, it will b up shortly

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[sparkinak]

19953

Here is the current tune file. Its not tuned just trying to get it to idle correctly. I sprayed the entire intake and throttle body with brake clean to see if I had any vacuum leaks but didn't find anything.

[LastCall]

19953

Here is the current tune file. Its not tuned just trying to get it to idle correctly. I sprayed the entire intake and throttle body with brake clean to see if I had any vacuum leaks but didn't find anything.

That was a pretty short log. But I did notice your IAC steps went to 0 and it was still idling at 1500 rpm. The engine will not be able to idle down to your desired idle speed if the valve is all the way closed and still pulling in 18 grams/sec of air. I would try closing the throttle blade and see if that helps lower the idle down. Shoot for 60 steps at hot idle. Air seems to be coming from somewhere.

Can you adjust idle with the DVT controls?

[sparkinak]

19954


I knew I should have asked how long of a log I should have gotten. I have another one I took that I will post as well. If my IAC is going to 0 how would I adjust that? I thought that was B4401/B4402?

As far as the throttle blade, I checked that the cable was seated properly and I checked the set screw which at this point I backed it completely of the blade linkage. Something that came to my mind just now is I wonder if my throttle cable is just tight enough it has opened that butterfly and that is why I am getting that tiny .4% TPS signal.

DVT, I played around for a quick second to see if it would do anything. The only thing I got to work was doing the injectors on and off. I did not mess with it long enough to try throttle as my brain was confused on why it was idling so high.

I'm also starting to wonder if there is something up with the IAC. Something like maybe the bore is wrong size or no deep enough etc. I see there is a difference between ls1 for 98/99 and the 00/02 models.

[joecar]

Does your throttle blade have a hole in it...?

[joecar]

Did transmission die from low pressure...?

[sparkinak]

No hole in the blade, just a ls2 Holley 90mm tb out of the box.

No tranny didnt die from low pressure? Did I miss or overlook something

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[limited cv8r]

Your log had quite a few EGR codes. Is there any way it could be getting air through the EGR at idle?

[sparkinak]

Your log had quite a few EGR codes. Is there any way it could be getting air through the EGR at idle?
No egr on this. I noticed that as well and will correcting the egr setting codes on next upload....

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[joecar]

...

No tranny didnt die from low pressure? Did I miss or overlook something

...What was the cause of the trans dying...?

[joecar]

That was a pretty short log. But I did notice your IAC steps went to 0 and it was still idling at 1500 rpm. The engine will not be able to idle down to your desired idle speed if the valve is all the way closed and still pulling in 18 grams/sec of air... Air seems to be coming from somewhere.
+1 I agree, air is coming in from somewhere.

Are you sure EGR port in manifold is plugged...?

Are you sure PCV is not pulling air in...?

Post pic of engine bay showing PCV.

[joecar]

No hole in the blade, just a ls2 Holley 90mm tb out of the box.

No tranny didnt die from low pressure? Did I miss or overlook something

Sent from electronic life sucking device.Ok, do this:

With engine running, remove IACV from throttle body, you should hear a large airleak at the IACV bore... plug the IACV bore using your thumb, what happens...?

Stick your finger inside the bore and plug off the air passage, what happens.

Is this IACV the correct on for this throttle body...?

[sparkinak]

Your log had quite a few EGR codes. Is there any way it could be getting air through the EGR at idle?
No egr on this. I noticed that as well and will correcting the egr setting codes on next upload....

Ok, do this:

With engine running, remove IACV from throttle body, you should hear a large airleak at the IACV bore... plug the IACV bore using your thumb, what happens...?

Stick your finger inside the bore and plug off the air passage, what happens.

Is this IACV the correct on for this throttle body...?
Thats what I will check today is make sure I have the right iac for that tb. In the instructions for tb it does not specify exactly which iac it needs.

I am kinda confused on the tranny question/comment. When I did the top end of the motor I decided to go thru trans while it was out. The clutches and steels were burnt so I replaced them with reds, replaced the sprags and then checked clearances etc.

I litterally hosed the engine with brake clean and I pulled the vavle and it lets air out and when I flipped it around the seal was good I could blow in. I also hosed that down and no response in idle.

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[sparkinak]

http://uploads.tapatalk-cdn.com/20160629/e602be197edb7c6d1ac33945be35a8af.jpg

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[sparkinak]

http://uploads.tapatalk-cdn.com/20160629/fe32b1838f00f849a0cf8f7f089ab109.jpg

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[sparkinak]

http://uploads.tapatalk-cdn.com/20160629/4eb2796a9cc9272af703bb600582d2bd.jpg

Hose clamp was on, checked hose for cracks and what not

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[LastCall]

Air is coming in from somewhere. Your set screw looks pretty far out. Can you back it down a few turns so the TB blades closes further.

If you can't control the idle with DVT controls, I think you may have an issue with the IAC or its wiring.

[sparkinak]

I backed the screw out so there was an 1/8th inch gap.

Im leaning towards either busted oring, wrong iac.

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[sparkinak]

Iac out revs up.

Thumb over iac hole idles down.

Finger covering air passage inside bore it dies.


The IAC I have is the correct one needed for the holley tb

[LastCall]

Iac out revs up.

Thumb over iac hole idles down.

Finger covering air passage inside bore it dies.


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So when you cover hole where does it idle down to (roughly)? Can you take a picture where the set screw is now?

Looks like the Edelbrock IAC is a factory replacement piece:

https://www.summitracing.com/parts/edl-36015/applications

[sparkinak]

19960

[LastCall]

That doesn't look like right. The tab on the throttle body should rest against the set screw and the set screw should be backed down to close the throttle blade more. The bigger blade shouldn't need too many screw on the set screw.

Is there adjustment in the throttle cable that will allow the throttle blade cam to go all the way back to set screw?

[sparkinak]

19961

No adjustment but here is the cable off so i know the blade is closed.

[LastCall]

Seems like something is keeping the blade cracked. When you remove the cable, the throttle blade cam should rest against the screw from the pressure of the spring.

Can you move the blade closed by hand so it rests against the screw? Also confirm that where it is now, the blade is actually closed?

[sparkinak]

http://uploads.tapatalk-cdn.com/20160629/938ce6e5241e10243be2f9edff34e275.jpg
http://uploads.tapatalk-cdn.com/20160629/b54835bf6b88fd46a7a61b1eae8b9e31.jpg
http://uploads.tapatalk-cdn.com/20160629/52f2af0107cbbe278937b5801438d704.jpg

Negative as far as being able to move butterfly towards set screw.

[LastCall]

The air is not coming from their then. I would focus on the IAC valve and its wiring. Air must be coming from there is not the PCV, EGR, or vacuum leak.

Let us know how it goes.

[limited cv8r]

The holley tech doc for the holley 90 throttle body shows an idle bleed as in pic attached. Does yours have this? If it does, is it adjusted correctly?

[sparkinak]

No its a different throttle body. Part number 112-576. No bleed screw

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[joecar]

...

I am kinda confused on the tranny question/comment. When I did the top end of the motor I decided to go thru trans while it was out. The clutches and steels were burnt so I replaced them with reds, replaced the sprags and then checked clearances etc.

...I'm trying to figure out if the tune caused the line pressure to be calculated low (which causes slipping)

( basically, in the PCM: low airmass calculation -> low torque calculation -> low line pressure calculation )

[joecar]

Also try this with engine running: remove the PCV air hose from valve cover to throttle body port, and use your finger to block off the port, what happens...?

[joecar]

19961

No adjustment but here is the cable off so i know the blade is closed.Does it close by itself so that the stop rests against the screw...?

[sparkinak]

Ill have to try hose deal tomorrow

On the tb it does not go any further back than where its at. The butterfly is closed with no gaps showing in the throttle body bore. Im still leaning towards iac after last test you had me do.

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[sparkinak]

Ok, blocked pcv hose on tb and no change.

I had him redo the IAC test joecar said to do and this is his response.

Does weird shit. Not sure. It will idle way down almost to do doe but idles low. Then idles up high, and as I move my thumb it changes nothing consistent

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[joecar]

...

Does weird shit. Not sure. It will idle way down almost to do doe but idles low. Then idles up high, and as I move my thumb it changes nothing consistent

...You have to pull the IACV out of the TB and look closely at the passages to follow where they go... and check that the IACV pintle matches up to the shape in the bore.

Also, check for gasket leak between TB and manifold.

[sparkinak]

Copy, im going to the shop tonight, didnt have a chance yesterday. And I will thuroughly look that flipping thing over. I did find the right IAC for it and delco along with gm part number. It has to be the 2000 to 2002 IAC from a firebird to make it easy

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[sparkinak]

I'm trying to figure out if the tune caused the line pressure to be calculated low (which causes slipping)

( basically, in the PCM: low airmass calculation -> low torque calculation -> low line pressure calculation )
So once I figure vacuum leak out, where can I go to look this info up so it will make sense to me. The trans now is built up with a 3900 stall torq. Shift kit blah blah. I dont want to dial motor in thinking im set and smoke the tranny.

[joecar]

So once I figure vacuum leak out, where can I go to look this info up so it will make sense to me. The trans now is built up with a 3900 stall torq. Shift kit blah blah. I dont want to dial motor in thinking im set and smoke the tranny.You have to keep an eye on the pid GM.TRQENG and on line pressure using a gauge on the line tap on the side of the case.

[sparkinak]

Busy weekend so didnt get to play on truck as much as i liked. Something about the IAC kept bugging me so I pulled it out, connector plugged in and then switched the key on. Iac extended about .25 inch. Looked at the oring and there was a slight gash in it. Not cut but just a part missing. Key off put the oring in the bore first, then installed iac and started it. Same thing but not. In stead of bam 1500 it slowly came up say 800 then 900 1000 1100 etc. I decided to just order a iac just to cross that off the possible list 100%.

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