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I have a 1998 C-5 with an automatic transmission; it's completely stock except for the exaust pipe and mufflers from the catalytic converter back.The car has California emissions. I use 91 octane (various premium brands). When coasting at 30-40 MPH; if I give a light throttle and the engine pings; part of the problem is that the transmission apparently is designed to move to 3rd gear (I would think it should be designed to stay in 2nd); anyway here's a list of everything I've done, the problem has gotten better but has not been resolved:
1)New fuel filter
2)Re-programmed the computer to stock GM specifications
3)High pressure injector and valve carbon flush (at GM dealer)
4)Fuel pressure checked and within specifications
5)New spark plugs
6)New MAF sensor
7)No 'check engine light' ever comes on
I need some suggestions and/or a referral to someone who had the same problem and it it fixed; a referral to a competent technician (someone who can solve problems when no 'codes' exist) in the Los Angeles/ Orange County Area of California.
From: Renaissance Festival TAZ the Wolfdog (R.I.P.)
Re: Off-idle pinging (Stevesetka)
You've probably got 'tip-in knock' which can be fixed w/ LS1 Edit's timing tables. I'd try Mike Morgan, http://www.mmsracing.com/, if he's in your area.