Montecarloss06

I own a 2006 Monte Carlo SS and I just cannot figure out this problem I've been having with Displacement on Demand. Every time i'm in overdrive and DoD switches from 8cyl to 4cyl mode once i'm lightly on the throttle and then I start slowing down and eventually come to a full stop the engine will vibrate and clutter. I noticed it's only in 4cyl mode because once i downshift to 3rd gear and it changes back to 8cyl mode it stops. When i'm in 8cyl mode and coming to a stop it brakes just perfect. Now i'm noticing when i'm in 3rd gear or overdrive it accelerates pretty quick but it surges like its misfiring or running lean like crazy and its pre detonating or something.So I plugged my scan tool in and pulled up Throttle Body Performance, Throttle Blade stuck closed, Ignition Circuit, High Voltage, Erratic Wheel Speed Sensor. I'm not sure if it's the 258 mm Electronically Controlled Torque Converter messing up or my valve body needs to be replaced because theirs a bad solenoid? Or my APP( Accelerator Pedal Positioner) is missing a signal so the Throttle Position or Solenoid Motor can't get pick it up so it messed up the solenoid motor causing the throttle body blade to close? I know I have a vacuum leak on my intake manifold, so I know it would run rich and possibly cause the throttle to be closed and then wear a groove in the bore but the fuel trims and PID'S throw me off. I know why my ABS is on but I pulled up the PID'S on the scan tool and only found my STFTO2B1(Short Term Fuel Trim Oxygen Sensor Bank 1) is pretty high (+30)(-27). It's throwing me off because when i'm driving it's so smooth and that LS4 sounds so amazing and she's running a normal 10:1 fuel ratio and at cruising speeds she's running right at 14.7:1 ratio normal ratio. I'm just stuck on this problem, and it's killing me that I just cannot figure it out. I'm ASE certified in A8 A6 A3 A2 A1, I have an Interview with Porsche coming up soon and I can't even figure out whats wrong with my car. It's embarrassing, so I need some help. All shared information with me is greatly appreciated!

Sint3k

Have you backprobed the signal wires with an osciliccope of the throttle body etc to make sure there is no dropout/glitching? Also, once the car reaches a certain speed its suppose to disengage 4cyl mode. It kind of sounds like its not disengaging correctly or it thinks its criteria for disengaging is not being met. Also, if you have a high fuel trim at idle, but not under moderate throttle, this indicates a vacuum leak... Also a intake manifold leak would not cause the engine to run rich, it would cause it to run lean... The fuel trims would run RICH, to adjust for the additional air.

rottonj

iTrader: (4)

Probably not your problem but when my car was experiencing the surging I cleaned the MAF and it corrected the issue. I believe the MAF can also cause misfire codes. I would start there, and clean the TB as well. Post back your findings.Good luck

Sint3k

Ive never seen a dirty MAF sensor from a car with a properly maintained filter... , lol

rottonj

iTrader: (4)

I have a properly maintained K+N , never over oiled. I am spot on with all my maintenance from day one. There you go, now you have seen your first one

Sint3k

Thats not a proper filter

rottonj

iTrader: (4)

Start another thread if you want to hash out the evils of a K+N filter , we can merge it with all the delete the evil DOD system threads lol

Sint3k

Yea i hear ya, but in all honesty for a living i do mobile diagnostics, a proper paper filter I've never seen MAF get dirty. I know theres a whole lot of, "claimed" benefits of K and N, but I've seen real numbers on Dyno's and plenty of dirty MAF's from using Oiled filters to tell me the hype is just hype. But that is all due to experience, and not opinion. Just saying, but anywho. Regardless I don't care, just sharing my true world experience.

rottonj

iTrader: (4)

So you run a paper filter. Damn, hardcore old school lol!

Sint3k

No, I use the KN filter that came with the turbo kit. I'm just saying what I've observed with them. Not that I don't use them