Rt66er

Not expecting diagnosis here, but was wondering if it's possible that an idle vibration problem I'm having could have something to do with the tuning/software. The car is a 2004 GTO with auto tranny. Problem is that after fully warming up, it exhibits a bad vibration felt throughout the car. It gets worse the warmer the weather, i.e., when the temps are 90-100 degrees outside and the A/C is engaged at idle in "D" it vibrates so badly that the dash starts to buzz. Feels like you're sitting on a big vibrating pager. This is not cam shake; this is a constant low-frequency vibration that, when it is really bad, you can actually hear. When the car is in open-loop it seems fine, but of course the idle speed it higher then, too. It exhibits this problem all the time (after warm up) but is worse with the A/C on and then a bit worse when the fans are running. I don't know if this is a contact-related problem or a malfunctioning part (IAC, etc.). I have had it back to the dealer 4 times; their only solution is to hang weights on the exhaust system to dampen out some of the vibration. I have tried adding bushings to the exhaust hangers to get rid of all play in the exhaust and this helps, but I think it is just reducing the symptoms rather than fixing the actual problem. Idle speed in D is 550 rpm (per Predator monitoring) and IAT sensor seems to be functioning. I can just rest my foot on the accelerator pedal and slightly raise idle rpm (maybe 75-100 rpm) and the idle smooths out perfectly. Could a saavy custom tuner fix this? Any suggestions would be welcome at this point.

RedHardSupra

iTrader: (1)

your idle is simply too low. put it up to 700rpm and problem will be gone. that's the quick fix. really what you have to do is adjust your RAF tables, but you can't do that with the Predator.

Rt66er

So are you saying that a custom tuner could, possibly, fix this? I have replaced the plugs (TR55's at .55 gap), checked the plug wires (750-800 ohms on all), installed a catch can, replaced all the vacuum lines I can, checked the brake booster for leak, checked extensively for any contact points. I really think it is something in the idle circuit or perhaps an accessory that is creating an abnormal drag. Would it be feasible to pull off the accessory drive belt and then start the car to see if the vibration goes away? Would this hurt anything to do for just a couple of minutes? I know the Predator will give you a load rate while in monitoring mode. Any other suggestions?