Well, a while back I printed out an illustrated instruction sheeto from Chilton online provided by Mazda Motor Corp., and it says to set the leading ignition timing to 5*TDC @ 750rpms and the trailing timing to 20*TDC @ 750rpms. Now, my problem is that my car doesn't idle at 750rpms when it DOES idle. So, could holding it at a point where the car will at least stay running (i.e. 1000rpms) affect anything substantially? I just need to know because I'm planning on checking my timing in a little while, so any help is apprecitated. Thanks.
-Lucas

 

... why won't your car idle that low? Rebuild? Ports?

I believe the ECU starts to advance timing somewhere around 1000 RPM. The initial set jumper will prevent it from advancing timing at idle, but IIRC it will still advance it at higher RPM. Not 100% on that though.

If you can get it to hang out below 1000 RPM, you should be fine.

Also, your idle problems may be related to timing. Just a thought.

-=Russ=-

 

It just refuses to idle that low. It kinda wants to shut off and then it kicks itself back up to about 500rpms and just kinda jumps around for a little bit before it dies. I can usually hold it at about 1000, give or take a hundred, but it won't do it on its own. I also figured the current timing setting could have something to do with the idle, so thats my main reason for wanting to check it, bit of a delema wouldn't you say?

 

There's a diagram floating around here somewhere (a picture, actually) of what the CAS looks like when it's timed properly. You pull the cover off the CAS, set the main pulley to one of the key marks, and tweak the CAS until it looks about right. It's *not* actually lined up with the receiver, IIRC.

This will give you a "good enough" timing to run/idle, and you can tweak it from there.

I suppose a good question would be, "What changed such that the engine won't idle?" Is it a new rebuild? Did you replace the CAS? Has it never idled properly?

-=Russ=-

 

As far as I know, its an original engine with a little over 187,000 miles. Secondly, whats the CAS and what does it do. Sorry for being a noob, but I'm just confused. Thirdly, I've had the car for over a year now and its never wanted to idle properly. I've replaced plugs, wires, 02 sensor, changed a ton of vaccume lines, and tinkered with the fast idle screw, but it still does the same thing. I've been told that I may have a manifold leak so I held it at an "idle" and sprayed ether all around the engine and nothing happened, it didn't increase rev. I've also been told that it may be a bad TPS, but I wouldn't know if it were. How would I go about checking the TPS? Would a voltage/ohm tester/testlight work or would it need to be torn down? Any tips would be appreciated.

 

vaqcuum leak

 

You need to do a search for "TPS adjustment"- you'll get all kinds of info there...

What I like to do after a rebuild is tune the car by ear for the first couple of hundred miles, in other words, stab the CAS as well as you can, get her started, then tweak the CAS until she's got the smoothest idle possible. What I've found is that I'm usually about 5* advanced from the marks when I do this. After she breaks in a while, I'll tweak her back to the marks.

You haven't just rebuilt, though, but what I'm getting at is it doesn't hurt to stray from the pulley marks that much to get her running smooth...

I'm with slpin, make damn sure you have no vac leaks at the manifolds (it's very hard to get underneath 'em to check 'em out properly. Make sure your ACV (right side of engine above the exhaust manifold) isn't leaking, and make sure any block-off plates you have aren't leaking...

Grab the FSM (factory service manual), and readjust the idle per the book, starting at square one. If nothing changes, you have other problems. Look for bad injectors, bad compression, etc...