Wierd engine noise!

[thefakie25]

I just got a 1990 GSX and the engine sounded fine the whole day then I took it out for a ride later on and as soon as I get into boost something makes a rattling noise from under the hood kinda sounds like a baseball card in a bicycle tire (might be a bad example but the best I can think of) And also wonder what grade gas I should put in it the car is completely stock.

 

[Blue95GST]

first off, always run the highest grade you can get at the pump, should be 93 for where you live, second on the sound is it constant or only when you boost? if when you boost, when you get time take off the intake piping to the turbo inlet and check the compressor fins, make sure nothing bent or rubbing, also check for shaft play while you're there, let me know how things check out, if its constant, let the car idle and try to pinpoint where its coming from cause right now we dont have much to work from, but good luck and keep us posted

 

[thefakie25]

Blue95GST The car only makes the noise under boost and from the drivers seat it sounds like its coming directly in front of me and from the passenger seat sounds like its coming from the front left also. But tomorrow if i get the chance ill check out the fins and for shaft play thanks for the help

 

[Blue95GST]

no prob, just keep us updated so we can help you figure out the whole problem

 

[WeaselHack]

I may be wrong but could be a bad CV? My driver's side outter CV sounds exactley like what you describe but only when i turn hard right. Its rather annoying but is getting replaced next payday.

 

[thefakie25]

first off, always run the highest grade you can get at the pump, should be 93 for where you live, second on the sound is it constant or only when you boost? if when you boost, when you get time take off the intake piping to the turbo inlet and check the compressor fins, make sure nothing bent or rubbing, also check for shaft play while you're there, let me know how things check out, if its constant, let the car idle and try to pinpoint where its coming from cause right now we dont have much to work from, but good luck and keep us posted

I took the intake piping off and the turbo has no shaft play and the fins dont rub. I let it idle and couldnt hear the noise at all but now when i gave it some gas the knock was there but it doesnt knock just idleing or driving without boosting im really confused it knock while driving in boost only and when in nuetral it will knock when i rev the car.

 

[funkbuster]

sounds like spark knock. If you put some bad gas in there, it could be the cause.

 

[thefakie25]

spark knock? How do I fix that?

 

[thefakie25]

when these cars were built well a 1990 anyway what grade gas were they tuned on?

 

[Blue95GST]

there all tuned on the highest grade of pump gas possible for the area, most premium runs from 91-93 octane, but either way, just always run the highest grade you can get at the pump