Just bought an 06 SS/SC last week. The car is highly modded. The mod run down is: 2.9 inch pulley, heat exchanger, 60# injectors, modular pulley system, 3 inch ZZP intake with K&n air filter, ZZP 3 inch header and downpipe, GMPP exhaust, euthanasia custom ported head, and Gm stage 2 clutch. I was told the car was dynoed and tuned at ZZP and has 260 whp and 218 ft lbs of torque. Anyway, when i bought the car it was having the notorious idle problem (idle bouncing up and down, especially bad with the heat on or clutch pressed down, etc.) Anyway, after checking out the thread on here instructing on how to fix the problem, I cleaned the TB and voila, no idle surge. After fixing that I couldn't help but notice that the car idles at around 1250 with the heat off and at 1100 with the heat on. When first turning the heat on it goes down to around 1000 for a second or two and almost sounds like it would stall if it went any lower than that. But I think I've read on here that normal idle is around 850. Any idea if perhaps the mods, specifically the tune or the injectors would cause the higher idle. It seems to run fine like this, i drove it around for a few minutes and let it idle for a bit checking to see if may it was just doing this while it was warming up but it never began idling any lower. When driving I also notice that when beginning to coast with the clutch engaged the car seems to drop RPM's pretty slow. Is this okay or does something need adjusted?

Sorry for the long read, just trying to lay out any and all information I can for you.

 

i dont want to read that long report so ill just go on a limb and ask whens the last time you cleaned your TB and or MAF

 

TB today, haven't cleaned the MAF yet. I've only had the car for about a week. Only reason I made such a long post was to lay it all out there. Sometimes left out details could be the problem.

 

there's a couple of different things that it could be. You mentioned that you have a ported head? That to me means that (obviously) **** got taken apart. Since you didn't do the work yourself, I would do a vacuum leak test around the head and all of the areas where you would have a vacuum leak (hoses, tb, intake, etc.). If those check out, I would check your 60's. They are notorious for having issues with idle. You could check to see if they are leaking, or even check the o-rings around the caps to see if they are hard/cracked. You might also have someone look at your tune just to look at your LTFT's and other readings.

 

I checked for a vacuum leak tonight and couldn't find anything but I don't have much experience with boosted cars. I'll check again and check the injectors as well. I was told the car was tuned by Tim at ZZP. Do you think there is any chance that this high of an idle is okay?

 

if you don't mind me asking, how did you check for leaks?

 

I was just sort of feeling around the vacuum lines. Feeling for any air that may be coming from anything. also listening close. not sure of any other way. is there anything else I should do to check?

 

soapy water is a good way. I would suggest hooking up a boost leak tester at the intake before doing that though. If you drop in psi during that test, it's a definite leak.

 

wouldn't a vacuum leak cause a drop in boost? I didn't pull in it after cleaning the tb but pulled at normal boost (16.5 psi) earlier today.

 

not necessarily. With my turbo'd lsj, I was racking in 21psi, even with a massive vacuum leak.

 

I checked for vacuum leaks today with water. I was still unable to find anything. I also searched on here a little deeper and it seems this problem isn't exactly uncommon after cleaning the TB. I found a few other threads concerning it. It seems like everyone says it sort of straightens itself back out after a few days. The CEL came on today. I'm going to get that checked ASAP. I'm hoping this isn't a major issue. I'm thinking maybe the MAF needs cleaned. So depending on what the code reads that may be the next step. I've heard cleaning the MAF is a little sensitive though and that it sometimes requires moving the front bumper. So I'm sort of dreading it lol

 

I hope you used soap with that water, because the idea is that there would be bubbles created around any leaks. And please let us know what the code is, but if anything I'm betting it will be a p0300.

 

yes, I used soap too. should have added that lol. But I had the code scanned today and it read "bank one system too lean". Guy at the parts store said I may have just got some fuel that had a little water in it. So I went to the gas station and filled her up again, after running it a few miles the light went off. So I'm thinking that was possibly the problem. My air fuel has been reading around 13.5-14 at idle and around 11.5 WOT. The idle has dropped to around 1100 RPMs now. I can drop it below that with the clutch but the car starts shaking as if it were going to stall. Anything below 1000 RPMs is horrible.

 

Anyway you can get someone to check the tune out for you? That's strange that it won't idle lower than that

 

only a moron would tell you that water in the gas bs check for a ex leak bfore the upstream o2 if there is no leak then shoot the wires from the upstream o2 to the pcm for continuity and voltage and if they are good try replacing the upstream o2 the reason why your afr is good in wot is you dont use the o2 for fueling it is done throlugh speed density

 

I don't know of any tuners in my area. Wish I could through. I read a few others on here saying Pretty much the same thing happened to them after cleaning the TB. A few said it just did it for a bit them dropped back to normal.

I'll check for an exhaust leak. The car is lowered quite a bit and the roads around here aren't the best. I haven't noticed a difference in the sound, but that doesn't always mean much.

I just don't understand why the cel went back off... damn cobalts :P

 

doesn't sound like it would be a vacuum leak then. I agree with mr b. Check your o2 sensor pre-cat. And check for any exhaust leakage. Since you changed heads, that would also be another area of concern. How are you checking for afr's??? Do you have a wideband? If so, what brand?

 

the cell will go off after so many crankshaft revoloutions

 

I am checking the air fuel ratio using by the gauge. It's an innovate with digital readout.

 

U are at 16.5 psi with a ported head and only a 2.9? Something dosnt sound right. Maybe the idle was set that high in the tune.

 

Yes, I am at 16.5 with a 2.9 and a ported head. Like I said before the previous owner had it tuned at ZZP. It's not causing any other sort of issues with the car. It's driving fine all except for the high idle. I may try replacing the throttle body sometime soon ad seeing if that helps.

 

The car has been to ZZPERFORMANCE 3 separate times. Everything was checked thoroughly MAF cleaned, throttle body cleaned, inspected for vacuum leaks, etc.. Car ran perfect other then rough idle. Car was at 261whp on ZZP dyno . Mainly when defrost or AC was when this issue presented itself This issue never came up until the 60# injectors were installed. Tim at ZZP said that 60's in these cars sometimes have issues at idle due to fact they are hard to tune with the software they use. The injectors are basically on ( spraying gas) or off. Creating the rough idle. I was told HPTuners gives slightly more parameters available with their software that can help with this issue but I never looked into it further. The high idle isn't due to vacuum leak, Tim set the idle about 200-250 higher rpm to try and smooth out idle more which did help but as him and I both knew it was just a band aid for the issue not a fix. You may want to swap the 60's for 42# injectors, these are easier to tune and can help fix the problem. Tim said 16-16.5 was perfectly normal with the cars current mods and in fact most stage 2.5-3 cobalts are here but the factory electronic boost gauge isn't responsive enough or accurate enough to show actual readings. This car used a mechanical boost gauge.

 

I remember you mentioning the 60# injectors causing a little idle trouble. Like I said, I fixed the jumpy idle by cleaning the TB really well. So it's idling steady now at about 1100-1250, depending on if the heat is on or not. Car is driving perfectly. No loss of boost or anything like that. At first I was a little worried when the car was idling steady that high, which is why I posted here. But after driving it awhile I'm not worried about it at all. And I have to admit, you built this car very well. Nice to see you on here, I know when we met you said you posted on here and the car has the CSS.net decal. I may end up swapping the injectors out sometime soon, I just want to find a good tuner in my area first.

 

Yeah I'm still on here quite frequently. And I'm not saying anyone on here is steering you wrong everyone has made valid points. I just came across this thread and wanted to give some extra info if I could. I have been a member on here for quite some time and everyone has been very helpful. It's a great forum to belong to. There is so much info that can be found here. And yes the car has always ran strong. No money was spared in making sure it was built properly.

 

With your mods at ZZP's shop should put you OVER 270.
I pulled 270 on ZZP's dyno and you have some stuff done to yours that I don't
When I pulled on ZZP's Dyno I had

• Simmens 60# Injectors with Harness
• NGK 1 Step Cooler Plugs
• ZZP 2.85" Pulley
• ZZP 3" Intake
• ZZP Long Tube Header w/ Catted Downpipe to Stock Exhuast
• OTTP Stg 1 H/E
• Dual Pass Intake Endplate
• LSJ Pheonalic Intake Spacer
• ZZP Stage III Custom Tune by Turbo Tim
• GMPP Clutch

So If you have a ported head and full exhaust, you should pull more then I did on the exact same dyno.
Also the 850 Idle is STOCK tune.
I have a Custom ZZP tune and my idle is 1000. Stays pretty regular unless I turn on the AC. When I'm moving, my car idles about 1200 rpm. Sometimes when the engine is cold while warming up the idle will be arround 1100 to 1200. If that's whats happening to yours you should be okay.
But I see in another post Tim set the idle high to help smoothen out the idle so I guess that's why.