I got my 7 back from the shop, and noticed two things wrong immediately while

installing the Holley pump, although it did it beforehand. The first thing was the bottom most carb linkage cable was not installed. That I can forgive, since there's a LOT of hookups to do when installing the carb.

Before that, I noticed the shutter valve small line was not hooked up. I hooked it up, and within a few minutes the engine started a steady miss, not so much a miss as a fast vibration. It coincided with engine speed. Also

while idling there was the hickup every few seconds, but not steady. It was an intermittent jump. I started looking closer and every time the engine jumped, so did the shutter valve. It was slamming open(or closed)

and I guess this caused the idle jump. I pulled the line off, and noticed the vacuum was steady, then it would suck very hard for a split second before returning to normal. Once I pulled the line and plugged it, all signs of the miss and jump were gone.



I am wondering what is on the other end of this line, causing the intermittent burst of suction? Is it one of the colored vacuum solenoids on the rats nest? The shutter valve is new, and was installed with the rebuilt carburetor.

I also noticed the blue and yellow vacuum switches on the rats nest, had their lines X'd over. I replaced them one at a time when I did it, and they were not X'd when I did it. So I can only imagine the mechanic did it, either the one at the carb shop, or the mazda shop. Would this cause the shutter valve symptom?

I'm having similar problems. I can't pass emissions because my carb is dumping fuel. Either that, or there's an electrical miss, so I think it's the carb since all my wiring looks brand new. It could be timing, but I doubt it. Have you found out anything about your issue?

Tyler

the shutter valves fail all the time, you basically want to plug the vacuum leak, and maybe wire it open

The only thing is that it's brand new, and I was charged $100 for it, plus installation cost? It hasn't been used more than 10 minutes in my presence, as it was unplugged, and has been since I tried using it. I am more interested in why the vacuum source to it pulses so hard that it slams it shut?? Does anyone know what could cause that?,,,,BB