i have a friend with a stock 94 z,and when he hammers it at anytime,when the rpm's hit 5800,the needle bounces,then car starts popping,then switches into a different gear,what could this be???

 

If it's happening at wide open throttle right around redline it's probably the EGR valve. Mine was doing the same thing because the bellows tore inside the egr valve creating a huge vacuum leak. The car ran perfectly normal until you tried to punch it the whole way, then it would run lean and pop-pop-pop- was heard under the hood till it shifted. Check it out...egr is heap and easy to replace. -Ryan

 

Sounds like the rev limiter to me.

 

I second that too.

 

yea, just sounds like his tachometer is waay off.. as all stock tachs are by no means accurate. unless you are referring to a aftermarket tach, then it may be more accurate. and if you're going to get into the EGR valve, make a block off for it and have it disabled in the program...

 

the main problem is not that they are inaccurate its that they are too slow to keep up with the engine. Same difference I guess. Another option if you do not think that it is your Rev Limiter would be your fuel filter or a failing pump... Good Luck...