I have seen the words "rough idle" alot on the forums and in the FSM, but I haven't found any clear descriptions of what is and what isn't a rough idle.
You see, I think my car has it. After warmup, at idle the RPMs oscillate between plus 500 and minus 250 of where I try to set idle. When I set the idle at 750, it would dip so low that I was afraid the engine was going to stall. In addition, there are exhaust pulses that are much stronger than others when idling. The car runs fine once you get past 1.5K.

 

Check your comression to see if its even across all faces of both rotors. That could cause the uneven exhaust pulses and maybe the idle. If the compression is fine, then you most likely have a vac leak.

 

Thanks, but first I want to make sure I actually have a problem here. Is what I described truely rough idle, or is it something else, or is it normal. I want to know what people would define 'rough idle' as. Then I can start troubleshooting.

 

I would call your oscillations "oscillations" and a rough idle more like "misfiring and/or almost dying." Oscillations are usually due to instability in some control system, so I'd recalibrate the TPS and check the AFM.

edit: the louder exhaust pulses are probably slight misfires, which in my experience is normal with rotaries.

 

Make sure that when you 'set' the idle to 750 you put a wire in the set jumper. Otherwise it'll drop down and try to die when you put any kind of a load on the engine at idle. Mine was set like this before i corrected it.

 

Honestly, I consider anything that isn't even (or a result of a port job) a rough idle. It sounds to me like either the TPS isn't set or a vac leak, though the thing with the initial set coupler could be it, as mentioned.

 

Just a thought, but when measuring idle, should the clutch pedal be pushed in, or should it be out with the transmission in neutral? I have been doing it the first way, but if it is the second way it might explain a few things. Like why my car was 'idling' at 1.5K before I tried to reset it. (I taught myself how to use a stick on the two hour drive back from where I bought the car, so maybe there were a few things I didn't pick up....)

And I did jump the coupler to ground, but I can't be sure about the connection. I didn't have any spade connectors, so I used a ring type that was just barely small enough to fit, and grounded it to a spot of bare metal.

Haven't had a chance to get to the TPS yet, but will check this weekend.

Oh, and 'oscillate' is correct spelling and usage.

 

did someone say it wasn't? Maybe I missed something.

About the clutch, just leave it out when you set the idle. Your grounding sounds ok, and I bet when you recalibrate the TPS your problem will be solved. Here's a fantastic TPS adjustment link:

http://howto.globalvicinity.com/gv_w...i=58&co=1&vi=1

 

If your car idles at a constant RPM level and you don't notice any misses or pulsing, you have a smooth idle. Correct idle should be at 750 (plus/minus 50). The most common cause of a pulsing idle is a TPS that needs adjustment. If you can't get the TPS to adjust properly, you probably have a bad one. Once you get the TPS adjusted, ground the initial set connector and adjust idle to 750. Take it out for a spirited 15 minute drive and come back and reverify the TPS adjustment and then reverify the idle.

After this, if you still have idle problems, then you probably need to look for vacuum leaks or plug and plug wire issues.

 

That's what I needed to know. Okay, check/adjust TPS, adjust idle A/F settings (while clutch is out, transmission in neutral). If that doesn't work, panic and scream while running in circles (so you don't get lost...) then pull out the FSM and start troubleshooting.

Hmmm, this might be information newbs should be provided with. Maybe after I get it all figured out I will make a new post with the info and get it archived...


Thanks everyone.

 

So I checked the TPS, and guess what? While the narrow range sensor was within specified parameters, the full range was way off. Must replace. I didn't bother to adjust the TPS, since I now know it is a POS. Unfortunately, it costs $362 from Mazdatrix, and I won't have enough money for a little while (poor college student who just bought a car and has been spending money on gas, oil, oil filter, gear oil, and paint). Should I try to get one from a junkyard until I can afford a new one? I need to get stereo mounting brackets from a junkyard anyway. Or could I get one for less from a Mazda dealer, assuming I installed it myself? (I am not going to pay some jerk for the privilage of touching my car.)

One thing I learned while checking the resistances was that you really want to have aligator clips on the meters leads, or two people, one to hold the probes on the little connectors and one to watch the meter and move the throttle.

While I getting out of the car to check, a gust of wind blew the door open, hard, and now it doesn't close like it used to, although I can't exactly describe how it is different. One more thing to fix/replace/repair...

 

There is no need to ever buy a TPS new. You can get them in the classifieds section for around 50 bucks (or less.) You can check junkyards, too.

 

Well, I like things that can wear out to be fresh whenever possible, it just gives me a little peace of mind. But thanks, I will have to check out the classifieds section.

 

The way I see it, even if you go through 6 or 7 used TPS's, then you are still ahead of buying a new one. And the chances of you going through more than 1 or 2 more are pretty unlikely. They don't really fail that often, so I don't consider them a "wear" item.