Discovered the power brake booster was not holding vacuum. This caused my idle speed to be erratic.

I've searched all the parts stores for a rebuilt. No luck, not available.

Also tried to find a rebuild kit, no luck.

Is there another booster that will work for a different Mazda or?

 

Get a used one. They should be a dime a dozen, it's a part that rarely fails.

Dale

 

Some interesting brake information (tech!) - MX-5 Miata Forum
The spec Miata guys have looked at alternate boosters for their cars.

page P17 fsm:
http://www.rotaryheads.com/PDF/3rd_g...g%20System.pdf

There is probably another Mazda booster that could work. I'm buying used but, an alternative could be an improvement and cheaper.

 

fyi my car is stock sequential. Idle speed was set to ~750 to 900 rpm (tps, idle control solenoid, linkage, fuel pump resistor, fuel pressure, etc all checked ok).

After driving the car or blipping the throttle, the idle would sometimes increase to ~1100 rpm, and other times return to the correct rpm.

Used a mighty vac at the booster inlet, and found it had a slow leak. Brake assist was ok when the engine was running, but, the leak was enough at times to overcome the idle solenoid range.

 

Have you check out the one way valve in the hose going to the unit? Make sure it is not also leaking.

How about taking the unit apart to find the leak.

 

I tested the booster with the mighty vac connected directly to the booster inlet fitting, it indicated a leak.
The check valve is in the vacuum/pressure inlet hose, so it was not the problem.

I found a source that will rebuild our boosters today.
Too late for me I purchased a used unit.

FD owners will need to ship it there for rebuild:
Home Page

Power Brake Exchange,

 

I just ran into the same issue trying to bring a car back that was parked for 6 years. I ended up buying a good used one from Fritz Flynn.

 

Finally replaced the brake booster. I had mine rebuilt by Power Brake Exchange, ~$145 shipped. Very satisfied with their work and customer contact.

My idle problem is finally solved. fyi, I have a street ported engine, downpipe, PFS intercooler, with stock tt ecu remapped by Pettit, stock idle air control valve etc.

It took about 20 miles of mixed driving, idles, etc for the ecu to re-learn the idle speed control.
It's now stable at ~800 rpm.

 

I have more brake booster if anyone needs one. However that said they will be sold as is

 

yup, Fritz is a good resource, I have purchased parts from him........