My car was running perfect untill a week ago. When the car holds full boost (12psi) it will make a VERY loud bang sound comming from the exhuast and the whole car would hesitate. The nexy day I changed my spark plugs and the problem went away 100%. Well a couple days later it started doing it again. Now it rarely makes the loud bang sound but the whole car hesitates. My LINK ECU is saying there is 0 knock. Its a 1990 FM2. Any suggestions?

 

Sounds to me like it could be hitting a rich point or an injector's sticking open?

Have you done a data log to find out what the ECU's doing at the time?

 

No i dont have the thingie (dont feel like looking for the name) that lets you download the data into the comupter. I should probly invest $100 in one.

 

I'd say going lean.

 

Call up flyin miata, thats part of the cost of an FM2 or link ecu. I bet they will have you cleared up in no time.

 

my car was doing the same thing when i would let off the gas and coast.
It was a really bad miss at idle and when i did a compression test cylinder #1 was almost dead.

now i gotta pull the head and find out whats going on

 

I'd say going pig rich off throttle. Whats your afr doing?

 

my guess would be rich too