4.8 Cammed, big injectors cannot idle

[Gus]

Before you flame me I've read the posts for idle and watched the youtube videos. I cannot get the afr to 14.6 and have a low idle; it's either 14.6afr and 1200 RPM or 10afr and 750 RPM.

Ive tried the RAF down to 7 but have went as low as 5 with it once it gets up to temp.I used a file out of the repository for a 4.8 with a similar sized cam but made some changes needed for my app (fans, tach, my injectors etc...) but airflow and spark are his.

My setup is as follows 99 4.8 swapped into 260z with a 6 speed, truck DBC TB, BBK intake manifold, Deatsh werks 18U-01-0060-8 60lb injectors for possible power adder down the road, trickflow 30602003 cam 228/230 @.50 .585/.585 112, and the HPT SD 1 bar tune, NGK AFX WB through the EGR sensor.

The other issue I have is that I'm running a CD009 transmission that does not have a VSS so the computer thinks I'm in first gear at idle all the time. I bought one of the first Autometer GPS speedometers which unfortunately does not have any type of signal output I can run to the VCM. If I make changes to the High octane table during RTT I have no noticeable idle changes. However if I RTT with the Idle tables the Base Idle spark in gear can get the RPM down to 950 if I 0 the timing out. How can I get the computer to reference the High / low octane tables? If I'm stuck with the base spark in gear it only controls up to 4800 RPM.

Attached is my current tune, a warm up log along with the HPT repository tune I referenced for mine.

cammed 4.8.hpt
cammed high idle.hpl
226-229 cam, idle air, ve, maf spark dfco, pseudo lean cruise 2007 4.8.hpt

[Gus]

Fogot to attach layout and injector data

GM injector data 18u-60.xls
sd.Layout.xml

[dermotw]

The AFR (02's or the WB) probably won't report properly at idle, with a cam and/or longtube headers(?)... Off idle it should, once the flow goes up. When its in SD (e.g. MAF disabled) it will use the low octane table if I recall right, plus at idle it (logically!) uses the idle spark tables, looks like you maybe tried to disable those, which I personally don't do, but its a choice I suppose... But in fact the MAX SPEED should be 0 not 400kph, (think carefully about how it works...). The way it is set now, it'll only use the idle tables...

It will use high oct table if no DTCs present related to the fueling (not sure how many can trigger it), else it uses low. Assuming all is ok & no DTCs, it will use a blend of hi/low depending on presence (or not...) of detected knock (KR), over time with engine running, meeting the KR qualifications, it will move to using entirely the hi table, any KR will bias it back towards the low. Your knock learn limit is set at 50kpa, if you idle at e.g. 60kpa it'll never learn at idle...

In the end I forced my car into OL at idle (only) as the only way I could set it to something sensible, since the sensors aren't accurate with cam overlap blah blah...

[Gus]

Thank you, I'm pretty green to it. What area is the 400 kph in that you mentioned? I'll change to 0

[dermotw]

Hi,

Spark >> MAX SPEED at bottom left, mine switches at 40kph, but thats just me!

Capture.JPG

[Gus]

Thanks, I have a followup question to that. I have no speedometer reference for the VCM due to the transmission and speedometer I'm using. Could I Zero both the speedometer numbers and only have it switch by the TPS settings above?

[dermotw]

If you set MAX SPEED to 0 then I believe it will never use the idle tables, just the hi/lo octane. The conditions in the tables are anded, that is, they must both be true. Using my example, imagine you are decelerating, in order to switch away from the main tables, throttle must be under 1.2% AND speed dropped under 40kph. When accelerating, from under 40kph, it will switch to main when you have over 1.6% + 44.8kph...

[dermotw]

I just had reason to check, I don't think speed and TPS are anded in this case, I think they're or'd, so what you want to do may be ok...

[Gus]

I found this in the help file. I did adjust and got a good idle even though it reads rich on WB.


Main Spark Table Selects
If either of these TPS or MPH values is exceeded the VCM will select the Main Spark tables, otherwise the Base Spark tables are used. The value minus the hysteresis is required to revert back to the Base table from the Main tables.

TPS: This value is the Throttle Position required to disable the Main Spark tables
TPS Hysteresis: This value is added to the value above as the threshold to activate Main Spark table in relation to TPS.
Speed: This value is the Speed required to disable the Main Spark tables
Speed Hysteresis: This value is added to the value above as the threshold to activate Main Spark table in relation to speed.

[Monty]

Before you flame me I've read the posts for idle and watched the youtube videos. I cannot get the afr to 14.6 and have a low idle; it's either 14.6afr and 1200 RPM or 10afr and 750 RPM.

Ive tried the RAF down to 7 but have went as low as 5 with it once it gets up to temp.I used a file out of the repository for a 4.8 with a similar sized cam but made some changes needed for my app (fans, tach, my injectors etc...) but airflow and spark are his.

My setup is as follows 99 4.8 swapped into 260z with a 6 speed, truck DBC TB, BBK intake manifold, Deatsh werks 18U-01-0060-8 60lb injectors for possible power adder down the road, trickflow 30602003 cam 228/230 @.50 .585/.585 112, and the HPT SD 1 bar tune, NGK AFX WB through the EGR sensor.

The other issue I have is that I'm running a CD009 transmission that does not have a VSS so the computer thinks I'm in first gear at idle all the time. I bought one of the first Autometer GPS speedometers which unfortunately does not have any type of signal output I can run to the VCM. If I make changes to the High octane table during RTT I have no noticeable idle changes. However if I RTT with the Idle tables the Base Idle spark in gear can get the RPM down to 950 if I 0 the timing out. How can I get the computer to reference the High / low octane tables? If I'm stuck with the base spark in gear it only controls up to 4800 RPM.

Attached is my current tune, a warm up log along with the HPT repository tune I referenced for mine.

cammed 4.8.hpt
cammed high idle.hpl
226-229 cam, idle air, ve, maf spark dfco, pseudo lean cruise 2007 4.8.hpt

Did ya get it figured out Gus ?

[Gus]

Sorry last Wednesday we welcomed a boy into the family. The only way to get it to idle down is put it around the 10-11 afr mark via wb. I know it was mentioned that the wb most likely wasn't correct at idle but I'm seeing black smoke and soot from the exhaust.

[jc052685]

injectors may be hitting their minimum pulse width.

[Monty]

Sorry last Wednesday we welcomed a boy into the family. The only way to get it to idle down is put it around the 10-11 afr mark via wb. I know it was mentioned that the wb most likely wasn't correct at idle but I'm seeing black smoke and soot from the exhaust.

Congrats on new member of the family Gus BIG TIME ...

I was looking over your #2tune file from above and firstly, stock the idle spark advance vs main spark advance tables go by closed throttle vs open throttle, the speed is disabled , even there is no way stock your going to get 251mph to enable the main spark advance.. the hysteresis 1mph is added to the 250 to enable main spark advance.. The idle spark advance tables are used in throttle is closed, not vehicle not moving, i could be wrong, but this is the way i am understanding it, once the throttle is closed 1.2% it then reverts to the idle spark advance tables, then once throttle is opened 1.9% it then reverts to the main spark advance tables..

Iv read your engine mods and what not.. really, i don't see why you have so much of the tune changed from stock.. a all stock tune with the idle running airflow bumped up a bit alone with the correct injector data and the timing tables set accordingly should run those engine mods just fine, but lol i totally could be wrong, also might i add, how do you know this tune you found in the repository even runs O dudes engine, people post up files they are playing with, trying to get to work.., you gotta be careful with those less they are verified stock.. need someone you can trust like a friend or a good known running tune like Matt's from sloppy mechanics

But yeah, if you run your idle running airflow around 7.50 to 9.50 g/s or so in the operating temps then your timing down a bit in the 20 to 24 the idle should fall into place nicely.. right now in the 30s+ is too high, really id go back stock and start all over again, thats always good practice when things are going wrong and your not sure why..

Let me ask what was the idle running airflow in that scan log above? to me it seems it was really high and you needed to lower the timing to get the idle to come down.. that just what it looks like to me.. but idk, also, if you will next file and scan, would be very helpful to post up the scan along with the same tune file you did the scan with..

Now know like stated up above, the WB or O2s are not going to be correct at idle probably anything below 1000 or 1200 do to your cam.. and your main spark both high and low should be put back stock.. your VE seems a little off, are you sure you can trust that WB.. you know since you have a WB and your still running MAF, STFTs, LTFTs and your stock O2s why not just MAF fail and tune your VE from your LTFTs and use your WB to verify.. make sure if you do try this to set your O2s voltage back to stock.. there are MAF fail videos on youtube, iv got one myself, like wise how to idle tune..

Also i noticed you had your O2s vottages changed not sure why, but b1 is different than b2 and also i saw your MAF table is really bumpy in the higher regions again not sure why but thought id let ya know, this can throw off your readings in part throttle vs VE will make it hard to dial in the VE will have lots of peeks and valleys in the same area that the MAF is bumpy in and like wise your O2s are going to throw your VE off too..

There are a few other things i noticed, but id start with correcting your idle running airflow and timing.. and like above, your main spark tables are not going to make a difference unless your open throttle.. and again make sure your injector data is good data, unless you got it from the dealer, of not see sloppy wiki page he has i know at lest 2 tunes running 60lbers

Ok sorry about all this jabber here, but man i just want to do my best at trying to help ya.. Let me ask, when you did these spark changes, your writing indicates your not moving/closed throttle.. need to be open throttle to get into main spark.. if you where open throttle im sorry, i do not know what the problem is, hopefully someone with more knowledge will come along and help ya.. Hope ya get this figured out Gus.. Oh and enjoy your new baby boy peace man

Oh and just wanted to say, i want you to understand, i do not know your skill level, for all i know you know me than me, and im telling you a lot of info you already know or info i could be completely wrong about.. i like i said, i just wanted to try and help ya Gus.. BIG TIME 2 thumbs up

[Gus]

Wow thanks Monty, I am very new to this so I appreciate all the information you provided. I do have a known good stock file but it's for the same year 5.3 that I pulled from my ecm. I'm guessing the ve on that would probably be off too and I should try to find a 99 4.8 truck to scan.

My thought process on the tps triggered spark was based on my lack of vss signal and was going to let the TB tell the ecm when to use idle spark. If that's incorrect I'll switch it out.

I'm open to all feedback. Thanks again

[Gus]

So I took your advice and used a 5.3 tune from a friend that way I knew it was unaltered. I did the following

put repo 99 4.8 Low/ High spark, VE table in it.
reduced low RPM VE due to cam and added 10% more across the board since I'm SD 1 OS
set idle in drive to 12 degrees and PE at 400-1200rpm with 0% tps to get it to idle down
put in my injector info
set my raf
set idle rpm

attached the tune and log from a 15 mile drive.

This was on 45 mph county road with some rolling hills and stop lights.

Still getting some idle hang and KR at idle.

15mile.hpl
back to basic Gary 5.3 added 10 to ve.hpt

[Monty]

I dont know sorry Gus, hopefully someone that knows more than me will come along.. I will say, id be looking at vacuum leak and looking at the knock sensors like wise the throttle body your using, make sure its functioning correctly, also make sure you have everything hooked up like all the sensors the VCM uses to calculate idle and what not, might even try zeroing out all the timing able adders, some people do this to make surte their timing is a set degree always, this will rule out any problems with your cam sensor or possiable cam install problems..

Also id try lowering the running air flow, though i don't think that would help, because really id be looking at a vacuum leak or a malfunctioning throttle body, check the butterfly at idle compared to the % showing on the scanner, might be TPS there are so many things that need to be ruled out.. Oh and i noticed again your O2s settings have changed..

Also it all could be just because of the injector data.. though that doesn't explain the timing issue, Gus, i am so sorry i do not know, but for sure, gotta rule things out in-order to find the problem.. Stick ya the stock injectors back in see what happens, if does the same thing, then you know its not the intectors..

But again really id be looking at a vacuum leak or throttle body issue and again the timing is odd too i noticed going from like 8 all the way up to 30+ in just one cell that can totally cause KR, but also id look at my knock sensors too make sure there is no cut or loose or nicked wires.. Also i noticed your idle spark is way different than your main spark.. the jump there can also give KR..

Gus this is about all i can think of right now, sure hope your able to figure it out man.. Just take your time, back track and rule out.. The problem will show its self.. O and again Congrats on the new family member BIG TIME peace Gus man

[Gus]

Thanks, I'm using the 99 in modified throttle bod and a bbk intake manifold with only one vacuum to the booster. I'll plug that off if the diaphragm is bad and start spraying with carb cleaner to see if rpm coms up. I'll keep working on it.

[Gus]

Sprayed injector and tb gasket area with carb cleaner and it almost dies so I'll start there.

[Gus]

Found my vacuum leaks and also noticed the gasket provided with the intake blocks off iac. I'll fix this and start over.
IMG_0652.jpg
IMG_0653.jpg

[Monty]

Found my vacuum leaks and also noticed the gasket provided with the intake blocks off iac. I'll fix this and start over.
IMG_0652.jpg
IMG_0653.jpg

Nice find Gus Hows tuning going for ya now, hope all is well.. peace Gus man