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Mazda Engine Performance \  weber tuning

weber tuning

Mazda Engine Performance Mazda Engine Mazda Tech
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replies 16
following 3
 
mazdafvr   +1y
weber runs great while driving but when in nuetral or taking off, it doesnt like low rpms. when i rev it from 900 rpms (unloaded idle) it does fine, but when the rpms are dropping, they drop about 100 or 200 rpms below idle and then slowly comes back up. when i take off i gota keep the rpms up a little over idle to keep from trying to bog or die. ive went trough tuning the carb and its as close as its gonna get, and doesnt change the symptoms. my dizzy may be off a tooth as it is tilted all the way toward the fire wall. but ran best that way with old carb. would even idle smoothly at 400 rpms. so im thinkin either i got a leak at one of the gaskets or the weber is just more sensetive to timing than the old carb. any thoughts?
dan woodland   +1y
Your distributor bolt should be close to the center of the mount opening. I'd take off the top timing cover and make sure you are top dead center then reinstall your distributor at the right position. Look in the Haynes or Chilton manual for where number one should be at TDC.

I had a similar issue (my distributor was cranked all the way one way) and resetting the distributor really helped. Now I'm fine tuning the carb - I had to get a replacement under warranty so I had to start all over again. You'll never get it right if the timing is not set correctly to start off.
mazdafvr   +1y
cool thanx alot man. if i can find the right screw driver ill do it on my next cigg break. lol. i know for sure the belts on tdc as i double checked b4 dad took it to southern va because i noticed my timing belt was a little loose.
for some reason my stock carb liked my dizzy to be a tooth off. it was origionally set correctly when i got it i just found it ran better that way for whatever reason. thats y i did the weber tho. too many vacums and weird shit to get it to run right. and without my ecu, id have to go and retune it everytime the weather changed.
Cusser   +1y
Some find they need to sand the weber adapter plates completely flat using a sheet of glass and wet/dry paper.

Sounds like a little vacuum leak to me, and a vacuum leak can affect the setting of the timing...
mazdafvr   +1y
yea i was afraid of that. sadly i read about it after the istallation. lol. im hoping i dont gotta pull it back off.... but if so owell. anything that is worth doing, is worth doing right. if moving the dizzy dont work ill spray some starter fluid in there around the gaskets and see if the rpms change. thanx for the input fellas.
mazdafvr   +1y
and one more question. when i took my old carb off i noticed standing oil in my intake. looked like the trail of oil came from the pcv valve. theres oil all over the valve cover by the pcv valve. would this indicate a bad pcv valve?
Cusser   +1y
Bad PCV valve or lots of blow-by. Or both.
mazdafvr   +1y
thanx cusser. and i think i found the leak u were talking about. under the intake mani theres a blue plastic thing with two nipples on it. i only saw one yesterday and plugged it but i didnt see the other one till just a minute ago. ill see how it drives when i leave work. should help tho. and ill get that pcv valve changed asap.
mazdafvr   +1y
im still experiencing a stumble at very light throttle. when i pulled my vacume advance and tried to suck air, i couldnt. like it was capped off or somthing. r u supposed to be able to suck air through it? and how the hell do i hook up the charcoal canister other than the one big hose that runs to the carb. theres a bunch of little nipples on the canister and idk what to do with them.
Cusser   +1y


That sounds like the thermo valve for the the vacuum to the EGR, in other words, that opens when the temperature is reached. So no vacuum from there, screws into the coolant passage.