hi all, Im new to cars an dont know as much soo, I have a 89 rs 5.0 5 speed. when I got the car the previous owners said they used premium gas because they raced it alot. Other people have told me I dont need that high gas to run my car rite since its mostly stock. when I switched to regular the idle kicks up to 2000 rpm and backfires (and the auto shop said it idles too high to tune it to factory spec.) but when I use premium it runs great. Is there something im missing or dont know?

 

check your ignition timing, perhaps they advanced it so far they needed to run high octane.

 

Fuel octane has no bearing on idle speed.

Higher octane does not produce higher performance but rather higher performance engines frequently need higher octane fuel.

High idle on TBI is frequently caused by a failed throttle body gasket. If the TB gasket is seriously degraded it can lead to a backfire on a throttle snap.

It is not inconceivable that the previous owner has tinkered with other aspects, tuning, timing, minimum idle air.

 

Listen to him, he got it dead on. Who ever you bought it from must have just been stupid.

 

Lol yea they did a number on the car prior to selling it, I damn near rewired the whole car. So is that an easy quick fix? or should I free up my weekend to get it done?