Slightly rough idle with erratic 02 sensor readings
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
I know that you took the intake off but, did you look carefully at the PCV boot that connects the PCV Valve to the intake?
It has a very bad rap for deteriorating (ROTTING) and cracking which produces a pretty good vacuum leak.
It has a very bad rap for deteriorating (ROTTING) and cracking which produces a pretty good vacuum leak.
Thread Starter
Burning Brakes
Joined: Feb 2013
Posts: 904
Likes: 296
From: Sacramento, California
Thanks Bill, I'll check all that stuff along with the fuel pressure. It's just weird, the car pulls good to redline and doesn't ever stumble or run bad, but it idles like crap, lol. Never would have thought a 22k mile car would run like this. I've had it almost 3 years now and have put 13k miles on it in that time.
Steve
Steve
Thread Starter
Burning Brakes
Joined: Feb 2013
Posts: 904
Likes: 296
From: Sacramento, California
So I checked the fuel pressure and it's steady at 59 psi and doesn't drop at all when I snap the throttle open so that seems good. I also checked the pcv hoses and couldn't find any cracks or deterioration so no vacuum leaks there. My next step will be to check the coils as Bill instructed. Weak spark does make some sense, but wouldn't that get worse as rpms increase?
Steve
Steve
Thread Starter
Burning Brakes
Joined: Feb 2013
Posts: 904
Likes: 296
From: Sacramento, California
I "think" I finally solved the problem after checking everything for air leaks and weak spark. A few weeks ago I got a P0174 code (bank 2 lean) and a CEL after some spirited back road driving. At first I was thinking crap this sucks, now what's wrong, so I did some research on the code and possible problems. Searching online brought me back here to the corvette corvette forum where I found similar problems from other Z06 owners. Several member got this code on their Z06 after installing a high flow air intake system which got me thinking. My idle problems and high LT fuel trims showed up after I installed the SLP Blackwing intake. Basically the higher flow introduced more turbulent air going through the MAF sensor which causes erratic readings and sometimes lean codes like the P0174. Since the Z06 doesn't have a screen I decided to try the high flow Halltech screen. After installing the screen my LT fuel trims went from averaging 20.1 to 10.1 and the erratic idle also went away. I've put a few hundred miles on my Z since then and so far no problems at all. 
Steve
Steve
Thread Starter
Burning Brakes
Joined: Feb 2013
Posts: 904
Likes: 296
From: Sacramento, California
I agree, but still better than 21-24 where I was at before. I'm surprised the screen made such a big difference. Since I'm not the original owner I can't be sure somebody didn't try tuning it and messed with the fuel maps or something. I just can't find anything else wrong right now.
Steve
Steve
Drifting
Joined: Aug 2014
Posts: 1,632
Likes: 190
From: North pole
I agree, but still better than 21-24 where I was at before. I'm surprised the screen made such a big difference. Since I'm not the original owner I can't be sure somebody didn't try tuning it and messed with the fuel maps or something. I just can't find anything else wrong right now.
Steve
Steve
Drifting
Joined: Aug 2014
Posts: 1,632
Likes: 190
From: North pole
I agree, but still better than 21-24 where I was at before. I'm surprised the screen made such a big difference. Since I'm not the original owner I can't be sure somebody didn't try tuning it and messed with the fuel maps or something. I just can't find anything else wrong right now.
Steve
Steve
Last edited by 04zjimc; Apr 21, 2019 at 01:09 PM.
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