Hi, long time since I've posted. Too much going on these days.

I've had my 1992 Vette for about 6 years, and in all that time, whenever I start her up, there is a brief "farting" noise (for lack of a better description) that follows. I've had my mechanic listen to it, and he seemed to think it had something to do with the ASR system. My ASR system is ridiculously sensitive, so much so, in fact, that at times when I make a quick turn at a traffic light it will kick on, which is annoying. But the actual noise almost sounds like a leak in a diaphragm someplace. Has anyone else ever experienced this? It doesn't seem to affect the performance of the car in any way, but it would be nice to put a stop to it, if possible. 

If the noise only presents itself after lunch at Taco Bell®; I doubt it's an ASR problem. 

😁

  ... hard to be serious about this.  I know that I have tried to reprogram the settings in my C5 -- it has memory of settings like seat position and mirror position, a/c temps, etc.  The seat made farting noises until it got to where it was supposed to be.  Leather getting pushed around, I guess.  Is that it?

It could be the ABS pump priming the accumulator in the ABS module, or just running it's normal start-up test. You could disable the ABS system by removing the fuse and see if the noise is still there. How long does this noise last? Couple of seconds, or longer?

Yes, the noise only lasts a few seconds at most. I did read a tech report on line that C4s prior to 1992 had some kind of startup noise issue with the ASR/ABS and that it was entirely normal, however, they did not describe the noise. There was also no mention of anything of the sort occurring in model years more recent than 1991. If the noise is the ABS system priming the accumulator, it would still be have to be abnormal otherwise other C4 owners should also be hearing it. On a related thought, does anyone actually make new replacement ABS/ASR components for the C4s? I just did a quick check and all I can find are used parts at eBay. 

My 1991 makes a noise, usually as I am backing out of the garage, not right at startup and per the owners manual its the ABS. The only other noise I hear is the fuel pump priming as soon as I turn the key to "On". It might be one of those "if it works , don't fix it things"

I believe the path suggested by Adams' Apple is the one to follow, as it would appear that the sound you are hearing is as he suggested;  I have heard the sound you are referring-to in several other GM products.  Since the sound is referenced in the Owners Manual, it is likely the increased level of sound in your vehicle might be due to bearing wear in the electric motor that primes the system, or just a noisy motor installed when your vehicle was manufactured.  

I have an 87. When I start the car, put it in drive, and start to move you can hear the abs test itself. Does the sound come from behind the back of the car? On the 87 the abs is either under the drives side storage bin or on the conv. Under the Bose speaker. I am not sure if yours is there, and it’s possible they changed it to test on start. It does sort of sound like a fart….insert wife joke here. If you have not heard the abs before, you’re not driving fast enough :)