hey guys i have recently purchased a 98 a4 1.8t quattro with 80,000 miles. i noticed after the fact that the original owner was using regular gas instead of the recommended 93 octane gas. i then turned my attention to the tapping noise coming from my motor. is this tapping noise from the valvues opening and closing incorrectly? and now that im filling up with 93 octane, will my motor run better and remove that tapping noise?

thanks

 

get your codes read at autozone. the better gas might stop the knocking but get codes anyway and post them here. then these guys will tell you what you need to do.

 

will code come out even if my check engine isnt on? and my friend has the computer for the odb2 connector so i can just do it with him. i will post the codes. thanks

 

You can have stored codes without a check engine light... but I doubt if the noise your hearing has anything to do with improper gas. Sounds like the previous owner was a bit of an idiot, though... you sure he used synthetic oil? If the timing belt hasn't been done, that'd be priority #1, as you're on borrowed time if it hasnt... of course that noise your describing could be a bit of valve clatter, which you'd end up fixing if your timing belt breaks and destroys the head.
Anyhow, sounds like the car has something to look forward to with you as its new owner... you don't need 93 octane, 91 works just as well (it was designed for 91). If you want to use 93 octane, might as well get it chipped and get APR's 93 octane software. www.goapr.com

Pray that it's had synthetic oil changes every 5K with the big OEM filter... If it is at 80K miles now, change it now, and again at 85, and 90, and 95... just a nice round # to change it at every multiple of 5. If its low on oil, that could cause a bit of noise like you describe. Bad gas would likely lead to knocking under load/high rpm.