Idle Going Lean At Stoplights

[hartigan85]

Since the Cam install I have been tuning my car with HP tuners using the tuning school learn at home beginners course. I have the Maf tuned and VE disabled. I am having an issue at idle when sitting at stoplights. When i am sitting there in gear the car will idle just fine 14.7ish afrs then all of sudden the car will start to shake more and i can watch the afr gauge go lean to 16:1. But if i put the car into neutral it will go back to 14.7:1 normal idle no issues. It only happens when the car is in gear and at usually every time i am sitting at a stoplight for more then 7-10 seconds. I am going to go and get a scan in the morning, just wanted to see if anyone on here has any ideas first.

[G8 GT V8]

When tuning, did you tune your MAF at idle and in gear? Might just need to do that. How are your STFTs looking when this happens? They should be adding fuel to fix things...

How does your MAF curve look in that area? Sounds like you need to smooth things out a tad...

[djchubbs]

I would check or listen for vacuum leaks since you have the intake off.

[hartigan85]

Well i got a chance to do a scan its really weird, when it goes lean both my STFTs go to 0. But before and after the lean spot they are normal, going up and down. I have attached my tune and scan from this morning. I tried to attach my config file but it kept saying that it was an invalid file. If you can look at the scan it shows it happening at 2:11 and 5:44. I have no idea what could be going on.

Edit: Looked through the scan again and noticed that when the car goes lean my commanded AFR is 15.7 ish. What would make my commanded AFR change from anything other then 14.7 except when going WOT and PE takes over?

11877 11878

[STL_G8GT]

Mine does this... thought it was a side-effect of a cam...? Also, when this happens it will push against the brakes a bit...

[hartigan85]

Yep exactly what mine is doing. Feels like it is bucking forward and back right? Pretty sure there must be a way to fix it because it stops when i put the car in neutral at stoplights. The next time yours does it put it in neutral and see if it stops.

[08G8V8]

I get something similar as well. I have a NGK air/fuel sensor and have it wired to my Aeroforce gauge. It typically shows a 14.3/14.4 AFR at idle when at a stop light. It doesn't always do it, but after idling for awhile at a light, the AFR will climb up to 15.5/15.6 and sort of shake a little, it will stay there for 5-10 seconds, then it will correct itself back down below normal 14.3/14.4 range, then back up to the 14.3/14.4 range. The STFT's don't look out of whack during this. If it was a vacuum leak, it would be doing it more often and always around the same vacuum level at idle, but it doesn't.

Not sure what it is.

[STL_G8GT]

Yes, in neutral it stops doing it, I've messed with it in the past... I thinks its normal cam manners... why it does it sporadically, I don't know. My aem does the same.... (wideband)... jumps to 15/16...

[hartigan85]

I disabled the catalyst test in HP tuners under engine diagnostics and that has seemed to stop it so far. I will know for sure tomorrow morning when i go for a drive.

[norm8332]

I disabled the catalyst test in HP tuners under engine diagnostics and that has seemed to stop it so far. I will know for sure tomorrow morning when i go for a drive.

That's it I bet. It's what I was going to suggest. But a side effect of messing with some cat settings could be fried cats - not sure about that setting though.

[zepcom]

This interests me. Please report back!

[hartigan85]

Well i drove around for a bit today and it didn't do it at all. Seems fixed anyway. I will see if it happens at all during the week going back and forth to work.

[08G8V8]

I disabled the catalyst test in HP tuners under engine diagnostics and that has seemed to stop it so far. I will know for sure tomorrow morning when i go for a drive.

Is this a different test than the catalyst efficiency test to prevent the P0420/P0430 codes?

[hartigan85]

Not sure exactly what its for, just know that it seems to have fixed the issue and i haven't had anything bad happen yet.

[G8-4-Speed]

If you watch command AFR, I bet it is 16.0. I have seen it.......

[hartigan85]

Yep my command AFR would go to around 15.7-16 and my STFTs would go to 0. I seemed to have fixed it by disabling the catalyst test. Do you think that was what is commanding the AFR to 16?

[G8-4-Speed]

Another trick with headers and/or cam is to raise proportional fueling from .038 to .050-.085. It is in fueling closed loop under Closed loop proportional base vs Airflow Mode.

Alot of times with cam and headers, there isn't enough fuel change to show up with all the added volume headers and/or cam.

[STL_G8GT]

I have the same "issue" but thought it was normal. I have the cats in the ARH system... would having this (catalyst test) turned off impact the life of the cats?

[G8-4-Speed]

I have the same "issue" but thought it was normal. I have the cats in the ARH system... would having this (catalyst test) turned off impact the life of the cats?

No, it is just a test, cats should be fine.

[08G8V8]

No, it is just a test, cats should be fine.

Is this the same test as the cat efficiency test, turning off the rear O2 sensors? I have my rear O2 sensors tuned out, but I still see this issue.

[G8-4-Speed]

rear o2's on or off, if the test is active, it will run it.

[STL_G8GT]

My tuner adjusted this test last time I told him it bumps lean then rich at idle... now its quite a bit better at idle...

[hartigan85]

Mine has been great ever since shutting off the catalyst test.

[bluegoat06]

It's just the Post 02 cat test, and the test would run this regardless if the car is cammed or not. the reason why the trims go to zero is because she goes in open loop to run the test, hence the reason you'll see 16 afr first, then she'll swing back to rich, then she'll settle down to 14.7 again, where you'll see fuel trims readings as normal.

[08G8V8]

It's just the Post 02 cat test, and the test would run this regardless if the car is cammed or not. the reason why the trims go to zero is because she goes in open loop to run the test, hence the reason you'll see 16 afr first, then she'll swing back to rich, then she'll settle down to 14.7 again, where you'll see fuel trims readings as normal.

So my car has been tuned so I don't throw the p0420 and p0430 codes. I thought this meant turning off the test. My car does this, so what did he change in the tune to keep the test active but not throw the codes? Dif he not turn the test off completely?

[bluegoat06]

You can disable the DTC's, but the test will continue to run anyways. to disable the test with HPT, go to Engine diagnostic, and disable cat test (Assuming you don't have cats) and post 02 cat test.

[08G8V8]

Thanks. Just wanted to know what was causing this. This answers that question.

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[bluegoat06]

No problem.

[hartigan85]

It's just the Post 02 cat test, and the test would run this regardless if the car is cammed or not. the reason why the trims go to zero is because she goes in open loop to run the test, hence the reason you'll see 16 afr first, then she'll swing back to rich, then she'll settle down to 14.7 again, where you'll see fuel trims readings as normal.

Makes sense, just weird that i didn't notice it doing it until i was cammed.

[G8-4-Speed]

What cam did you end up going with?

[hartigan85]

I ended up going with a pretty small 224/230 .581/.590 114+2, which I believe is similar to the livernois stage 1. I will be supercharging when I get back from the desert in 4 months so I figured this cam would decent for when I do.

[G8-4-Speed]

Good choice! Should run great. You'll need a 2.8 pulley on it with a BAP and methanol.

[hartigan85]

What do you think about a 3.0 pulley and no methanol? Not really sure I want to run meth right now, maybe later if I want more power. Shooting for between 525 - 550 WHP on no more then 8 lbs. I plan on ordering the Maggie 1900, 60lb fast injectors, 3.0 pulley, and BAP before I get home so It will be waiting for me to install when I get back.

[Daniel Linnett]

Buy my rear OD rip kit and keep current front pulley on.


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[hartigan85]

Buy my rear OD rip kit and keep current front pulley on.


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How much boost difference adding the rear OD? I would consider it if i was buying parts now plus I'm not gonna have the money for all the parts I want til at least the beginning of February.

[Daniel Linnett]

There is no set number, it is dependent upon many factors (this is the answer I was give from Magnacharger when I asked about my Cog and From Left Coast 32) You will gain probably 2-3 min and every 1psi is 20hp roughly

[johnbell2]

Skip the 1900 and go w/ the 2300...

[hartigan85]

I thought about that but the 1900 is enough to get me to my goal, 550 WHP. I just can't justify to the wife the need to spend an extra $500+ for the 2300 when the 1900 will get the job done.