Hi

yesteday i started my car and it started nicely. then about an hour later the idle would go crazy, the car almost turned of on me. So i left it as it was. Now it idles at about 100-200 rpm. what i noticed was that when the key was turned to the on position with the engine off i could hear the fuel pumps( pierburg + stock) working. I could hear the fuel running through the system. I have not noticed this or the loud noice before. I have 300cc supra yellow injectors with the resistors. I checked the car for any vaccum leaks and nothing. i removed the four spark plugs and they were really black and sooty.

Has anyone had this experience. What can it be???

Thanks

 

Bad fpr and sticking fuel pump relay. Your pieburg should not be on out of boost. So this tells me the fpr is fucked up. The fuel pump is supposed to be switched by the afm after the initial priming pulse, ergo bad relay somewhere.

 

the Pierburg will always be on as long as the oem pump is on Richard.

 

What fuel pressure regulator should i check. the Begi or stock. also it has two relays the pierburg relay or the stock relay. the pierburg relay was added a while back because it was blowing the stock relay.

i know that when i turn the key to the on position the fuel pump makes noice for about two seconds then it doesnt make any noise. but in this instance it makes noise and it wont stop. the fuel seems to be running through the whole system. can anyone explain the really black spark plugs unless its a bad idle because i need to change the spark plugs too.

thanks

 

So i took the miata to my uncles shop. i used the scanner to check whats going on. I got two codes. One was the air flow meter or electrical connection. the other was intake air temperature sensor. the car runs rich on idle, but while i was driving on the freeway it was fine. has anyone received these codes or had a similar problem. I dont have time to check it much i have a thermodynamics exam.

thanks

 

Like i said check your afm inside read brains faq after the exam. In a nutshell the wire you have there in the afm to control the FP is screwed up from to much heat of vibration. And your fuel pressure regulator wichever one controls the base pressure is most likely clamping down to much. But i dunno much about peiburg systems as Scot so nicely pointed out.