alright guys i have a problem with my 88 N/A RX so im in dyre need of your help.
the car will stay running just fine and when i went to run a diagnostics they told me i had a bad fuel pressure regulator and i didnt get around to fixing it till now. the other day i left my neighborhood to get gas about 1 mile down the street. when i got on it out of my neighborhood it studdered constantly after 4000 but on the way back it ran just fine. i didnt drive it the next day but the day after i went to the same gas station and it studdered all the way up there and i actually had to pull over because of the huge lack of power. i checked all my connection and then limped it back home. ive also JUST put the mechanical fan and and a fuel cut off switch on the car. i changed the plugs and there was a little improvement but not much. i changed the Mass air flow sensor and that helped a little but barely any. its making a funny noise when running. the motor has less than 50,000 on it and its street ported with 550 secondary and stock primary injectors (whatever they are) the motor becomes very shakey when it idles at a low rpm. it just started all of this all of a sudden. i checked my fuel pressure and its around 40psi at the pump. this has stumped me and i cant figure it out. you guys seem to always help each other out so i figure yall could answer my question. thanks guys hope someone out there knows whats goin on with my 7.

 

Possible problems:
Vacuum leak, check the vacuum lines.
Plugged fuel filter
Air leak in the air plenum or whatever mazda's name for it is (the black hose/pipe that runs from the AFM to the throttle body)

 

What kind of funny noise? Like a vacuum leak? ~rich

 

no like a vibrating noise. also the fuel pressure right at the pump is 35psi(idle)
40psi(3000RMP), if that makes a difference. im bout to change the fuel pump and see if that changes anything. there is no leak in the intake piping. the thing i dont get is that it started it one day when the car was cold but then when it got warm it ran fine, then it started it constantly and has not quit. im gonna try to change the injectors and the fuel pump to see if it changes anyhting.

 

dont just start changing things. if your pump is putting out good pressure at the pump than it is okay. I would check the prssure at the output of the fuel filter rather than at the pump itself. That way you know if the filter is flowing.

Make sure your mass air flow sensor is plugged in, same with the thermosensor at the back of the waterpump. If all that checks out take a look at vacuum at idle, with an actual guage not just listening to it.

Check your crank angle sensor, first that it is plugged in properly as well check the resistance as per the manual. Make sur ethe timing is right.

If after all this your car is still acting funny and these tests all check out okay, I would look at doing a compression test.

 

well i figured it out, its a blown rotor,.......<edited for flaming>

 

Sounds like the car was improperly modified... why blame the motor??? Blame the idiot that hacked up the car.

 

hmm sorry icemark, didnt mean to flame, i was beyond mad. thanks for editing. only thing i dont understand is how it blew after only 35xxx miles.