: Surging issue



KoNZ
08-16-12, 12:41 AM
My baby is a 2009 V sedan... I have done the Hennessey 650 upgrade plus Corsa sport mufflers, 20" Savini wheels with Michelin PS2 rubber, D3 stab bars and a bunch a other cosmetic stuff. Car runs great handles awesome (registered 1.1G on the meter the other night) is a helluva ride but I have an issue that me and some really good GM techs and Hennessey techs can't seem to figure out... It is a 6-speed manual. This issue started after I did the Hennessey upgrade...

When I first start the car and drive it, when I have my foot on the gas, even only 1% no issues at all... But if I lift off gas altogether and am coasting I get a nasty surging, about once per second where the car surges up to about 35% throttle... I know for certain that it is the ECM switching between open and closed loop for sensor input, which burps the throttle to 35% then to 0% and just keeps doing it... Will surge all day... However, if i get the car over about 90 kms per hr (or about 55 mph) only one time, then the surge goes away and I can drive all day with no issues. If I shut the car off, even for one second and restart it, the surging comes back until I get the speed over 90 again then it is completely gone again and will run forever without the surge until I shut it down again and refire... Then it's back... It is super annoying!

Hennessey 650 upgrade, mechanically, is under drive pulley for supercharger, intercooler, headers with high flow cats, 160 degree thermostat, ECM flash, cold air intake with K&N filter and then I put the Corsa mufflers on it... Supposed to be 666 HP now.

Have replaced all '02 sensors, MAF sensor, nitro smoked the entire intake system with no leaks and still can't get rid of this surging... But again, get the speed up to 90k/hr and its gone. Almost like the MAF sensor needs enough air past it to read correct or something. For sure ECM is switching from open to closed loop and causing the surge...

If anyone has any thoughts or suggestions for what to check, I'd be grateful for the insight!

KoNZ
08-16-12, 01:17 AM
I should also mention that I have run car with original ECM flash, factory ECM flash, second Hennessey ECM flash and surge is present with all... So I don't think it's a software issue!

I will also say, that I just subscribed today and have read a number of threads and am happy to have found this group! Everyone is entitled to their opinion but even if I had to buy another toy car tomorrow, it'd be another V sedan! Looks good and with the right upgrades is wicked fast, out handles most factory super cars, sounds awesome and with air conditioned seats and the pop up nav and all the other toys, is way better than the 'vette or most other competitors. I also put 2 JL 12" W3 subs with a good amp off the factory system and it pounds!

So long live the V, rock on and thanks for any knowledge and insight to my only real issue with her.

Dogbreath
08-16-12, 09:20 AM
I know nothing about this, so I'll offer a guess. Some sensor is either broken or disconnected. My guess is something like the TPS, or Cam position sensor, but again I have no idea what I am talking about.

Derkyb
03-14-14, 04:19 PM
I have the same problem all stock except airaid and muffler delete, will let u know what I find I also noticed mine is only in 3rd or 4th gear and it started doin it after I did a hard run. I think its the ECM like u said.