Hey, i have found this topic and i guess it is a sollution to my problem.
I want to ask those of you who have tried this mod:
1.Since then no problems occured?
2.The idle is so smooth till now?
3.The filter needs to be changed after some weeks of use?
Thank you for your ideas...
P.S. I forgot to mention that i have the 1600 DOHC motor, but the same problems!
My wife bought her 93 RS new, and she says it has had this idle problem since it was new. The dealership couldn't figure out what to do...
I think it is a bad design. I've been reading up on all the systems in this car since I'm rebuilding a BP and getting ready for a swap.
I've been in engineering with computers and electronic systems since the stone ages, and I can tell you that feedback loops are nasty to deal with. When you take that hose off and stick on the filter, you are breaking a feedback loop in the system. I think Mazda didn't pay enough attention to this.
I suspect that a perfectly tuned new engine with MAF and everything else all clean and pretty, you would not really notice this problem, but the system is hypersensitive to any disturbance to the system.
Think of it this way, these tiny engines generate almost no power at idle. A tiny change in the load causes the RPMs to drop. The ECU notices this, but a small amount of time has elapsed. Then the ECU changes the idle adjustment, and some more time elapses. The idle is still low, so the ECU adjusts some more. Then the RPMs start to pick up, and they climb past the desired point. The ECU notices that and starts to back down, but this also takes time, and soon the RPMs are too high. This is an oscillation in the feeback loop, and if it's at a resonant frequency of the system, it can increase in amplitude until the RPMs drop too much and the engine stalls.
I suspect that removing this tube retunes the resonant frequency to a point where it is damped, and you therefore no longer see the problem.
For a quick lesson in resonant frequencies and damping, imagine taking the shocks off your car and then hitting a small bump. With just the springs, the car will bounce up and down for a long time. All feedback loops require a certain amount of damping to avoid resonance.
I suspect that with these wimpy engines Mazda pushed up the reaction of the ECU to a drop in RPMs and overcompensated.
I've tried the filter, but also have cleaned out my entire intake system, along with idle air control valve underneath the throttle body.
In my opinion, it did not make much, if any, of a difference.
I think i might have been able to clean the IAC valve out a bit more, but I really doubt that would have made much of a difference.
Again, everyone's motor is probably in different shape, and everyone's mileage will vary (pun intended )
Originally posted by hondah8er13: well i don't know if this will help you out or not, I was having the same problem with my 92' 1.6L sohc automatic.... anyway i ended up doing a full tune up, O2 sensor, added 4 new grounds, also reset the idle from the diagnostic plug, and one of those fixed... since i did them all at the same time i'm not sure which one fixed it.... sorry but hope this helps..
I was hopeing you could give details/instructions on how to reset the idle from the diagnostic plug.
The diagnostic plug is located on the firewall (drivers side). Open the cap and look under the lid. There will be a diagram there. One will say "Ten" and one will say "GR". Warm up the car to normal operating temp and use a wire to connect the "Ten" and the "GR" together (while car is running). You may notice a change in the idle as soon as you connect the wire. Now, adjust the throttle screw on the throttle body slowly (it is sensitive). Right lowers the idle and Left raises the idle. As soon as you get the idle to where you want it, remove the wire and the ecu is set. Your idle problem should now be fixed.
Originally posted by White92MX3: The diagnostic plug is located on the firewall (drivers side). Open the cap and look under the lid. There will be a diagram there. One will say "Ten" and one will say "GR". Warm up the car to normal operating temp and use a wire to connect the "Ten" and the "GR" together (while car is running). You may notice a change in the idle as soon as you connect the wire. Now, adjust the throttle screw on the throttle body slowly (it is sensitive). Right lowers the idle and Left raises the idle. As soon as you get the idle to where you want it, remove the wire and the ecu is set. Your idle problem should now be fixed.
I thought that you begin while the engine is not running and unplug after you turn it off.
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