I have a 89 na 5 speed vert. Bought the car and for a week it drove great and had 0 issues and all was well. It did have a few cel codes (8,9,10,11,12,18) which scared me but it drove perfectly well. Out of that whole week it, “cut” rpms once at full throttle in 1st at ~7500rpm. Didn’t think too much about it bc it happened so rarely. The problem proceeded to get worse and worse after that week. It now happenS at partial throttle as well as wot and at different rpms in every gear. It runs and pulls perfectly strong until it decides to just violently cut and then I get back on the throttle and it’s fine again. I’ve replaced the afm, tps, plugs and wires, and fuel filter. I’ve reset the timing and set the tps multiple times. I cleaned every ground I could find in the engine bay. After all do this I only have codes 9 and 11. Which I’ve looked up and they shouldn’t produce the symptoms I’m experiencing. I’ve looked for bad vacuum hoses and everything looks connected and all hoses have been replaced so none of them are cracked or anything. Haven’t done a compression test but the car performs so well when it doesn’t “cut” that I highly doubt it’s compression related. Hot starts and cold starts quick. I have an o2 sensor already on its way to my house and we’ll see how that goes. I have a feeling it’s a wonky coil pack that randomly decides to poop it’s pants. Any help would be greatly appreciated.

 

you said all vacuum lines were replaced. did you put the restrictor pill in the line going to the pressure sensor? if not get one part # 8931-13-986 mazda calls it a orifice. put it the vacuum line going the pressure/boost senor on passenger strut tower and see if it makes any difference. had similar problem with one of mine and that was what was causing it. hope it helps

 

I wasn’t the one who replaced the vacuum lines but I will check that for sure. Which end of the vacuum line should the pill be at? Thanks for the response

 

does not matter but all the ones that i had it was close to the actual sensor