Idle Speed for 1989 Mazda Familia Interplay 1500CC

It is 16 Valve DOHC, I am running 98 octane in it and it warm idles at 1500RPM. How do I set the idles speed or what should the idle speed be.
Should I even run 98,
Suggestions accepted

driver_nomannz123, Mar 24, 12:12 am

91 octane is the minimum and absolutely fine to run.
Warm idle speed should be around 850-900rpm.
Cold idle in a manual is around 1250rpm, auto is around 1750rpm.

driver_jasongroves, Mar 24, 12:22 am

Here's a picture of the location of the idle adjustment screw:

To be honest though, the idle screw doesn't generally move around on its on, so I would be looking for other reasons as to why it is idling so high.
A faulty temp switch/sender is a possible cause off the top of my head, as if the switch is telling the carby that the engine isnt up to running temp, then the carb will assume that the engine is always cold.making it fast idle (essentially auto-choke).
Another possibility is a faulty thermostat.if its jammed open, the operating temp will stay low.
What does the temp gauge read once the engine has been warmed up!

driver_jasongroves, Mar 24, 12:28 am

On a plus note.generally a very sturdy and reliable engine with plenty of parts and support available (including from Ford).
What is the condition of the coolant!

driver_jasongroves, Mar 24, 12:30 am

One last question.:)
Whats the service history like!

driver_jasongroves, Mar 24, 12:33 am

Hi Jason, it appears to run on the cold side of the temp gauge, not quite to half way where one would expect it to be. Say between midway cold and the halfway mark.
Coolant is straight waterand I will be flushing itout and refilling it with coolant with Antifreeze etc.
Will check the temp sender and the thermostat in the morning.
Other than that the cam belt and water pump were changed 10,000 Km ago and wonder whether it is timed properly. Will look at the first 2 options first.
Just bought it today

driver_nomannz123, Mar 24, 12:40 am

Yeah temp sender and thermostat are dead easy to check.
Good on you for doing it yourself:)
Proper coolant/anti-freeze has different cooling properties to straight water, so that's a damned good start.
Timing is a possibility.could be a tooth out, but I would expect more severe symptoms (rough running for one).
I do have the info for timing etc etc if you need anything.

driver_jasongroves, Mar 24, 12:46 am

Service History is OK, cambelt done , water pump all done.
Suspect the coolant and the Temp sender and or thermostat.

driver_nomannz123, Mar 24, 12:46 am

Actually.strange that belt and w/pump were changed and no one bothered to use proper coolant!

driver_jasongroves, Mar 24, 12:47 am

Tridon thermostat part # TT240-192

driver_jasongroves, Mar 24, 12:53 am

Does not run rough, smooth acceleration and very good pickup with speed.
The lady that sold it to me said a few minutes ago thatthat she bust a hose and her brother put a new one on and filled it with straight water.
Yes timing would be handy.
You are a great help.

driver_nomannz123, Mar 24, 12:57 am

Just as an after thought, check the metal heater hose under the exhaust manifold for corrosion. Just a precaution really, as have seen them rust through before when proper coolant hasn't been used. Unlikely though.
Will see what info I have, as I just realised that the cold idle info I gave you was for a B6 (1600) engine:)

driver_jasongroves, Mar 24, 1:01 am

driver_jasongroves, Mar 24, 1:05 am

Hi Jason, if you can give the B5 idle speeds or are they the same

driver_nomannz123, Mar 24, 1:22 am

Idle speeds are within 50rpm of each other.

driver_jasongroves, Mar 24, 1:47 am

Actually, idle speeds are given in link @ post #13

driver_jasongroves, Mar 24, 1:49 am

98 is total overkill for that engine. Run 95.

driver_taim3, Mar 24, 11:22 am

I had the 93 model of this with the 1500DOHC engine. It too would idle quite high when cold, but at normal idle would be between 600-750rpm. Also should you be running on such a high octane! I ran mine on 91, no trouble!

driver_family007, Mar 24, 1:23 pm

I run ahigher octane in mine every now an then to give the engine a clean out, mine idles at 500 to 600 when warm. temp always just sits under the wavy bar.runs on 91 can pink thou when we get crap low octane fuels- generally december , jan. feb. Oil leaks outa the distributor . Have blown frost plugs in the past. comfortable speed it likes for crusing is 120Km unfortuntlay.

driver_gabbysnana, Mar 24, 7:43 pm

You have to short the diagnostic box before moving the idle screw.

driver_karstuff, Mar 24, 8:09 pm

Would the 98 Octane cause the engine to over rev.
I think when I had a little 91 in there it idled around the 1000 RPM on the in dash counter.
But I am changing the Thermostat and Sensor, also the air filter looks quite dirty.

driver_nomannz123, Mar 24, 11:54 pm

No, higher octane fuel wont cause the engine to rev higher.

driver_jasongroves, Mar 25, 1:14 am


driver_jasongroves, Mar 25, 1:14 am

Actually, might be worth checking for air leaks around the manifolds as this can cause erratic idling.
With the engine running, spray some CRC or similar around the manifold flanges.if the idle speed changes, then you have a leak.

driver_jasongroves, Mar 25, 1:16 am

Can you explain the logic behind that for me!

driver_moosie_21, Mar 25, 12:40 pm

To alter idle one must first open the diagnostic connecter and link the "ten" and "ground terminals.Same for altering timing.

driver_karstuff, Mar 25, 8:22 pm

In 1989, wasn't this only on the purple cars!

driver_jmma, Mar 25, 8:48 pm

After all this I think spending money to have it hooked up to a diagnostic machine might be even better as a diagnostic machine should show where the issue is.
One of the regulators in the engine bay fuse box was chattering away as well, will take it for diagnostic test.

driver_nomannz123, Mar 26, 1:10 am

You can do a diagnostic test yourself:)
There should be a small box beside the battery, that's the DLC (Diagnostic Link Connector).
Here's the info:

driver_jasongroves, Mar 26, 1:40 am

If any faults show, post back with the code and I will give you the codes meaning as there is too many to post here:)

driver_jasongroves, Mar 26, 1:43 am

Hi Jason it does have the small box, but I do not have a test light, are these easy to make or can I buy one. Also bridging the data link connector, are these easy to do.
I thought of some thing, will a test light used to test fuses do the same thing and will that give me codes.

driver_nomannz123, Mar 26, 1:51 am

You can make one
but it can be a bit fiddly and time consuming.
My mechanic mate has one which I use, so they are available (you need an LED test light for this model).
Jaycar may be able to help or someone else around here may be able to point you in the right direction.
Bridging is a piece of cake, you just use a paperclip or something to connect the GND and TEN terminals together and leave it connected while you use your LED test light.
A normal test light wont do sorry as the resistance and output is wrong.
Sadly, yours is slightly more complicated than most vehicles or that error to diagnose.but still simple enough.
With the majority of Jap cars, you just bridge 2 connectors and count the engine light flashes.

driver_jasongroves, Mar 26, 2:08 am

I've got a multi-meter for serious testing.but more often than not for basic stuff, I just use a home made tester (an old 12v bulb in its connector, usually a brake light with some extra wire attached):)

driver_jasongroves, Mar 26, 2:12 am

Did you do the basics like check for manifold leaks, thermostat etc!

driver_jasongroves, Mar 26, 2:13 am

Now a thought is where do I find the water temp sensor, it where the Thermostat is, or is it on the block.

driver_nomannz123, Mar 26, 8:07 pm

Usually there's a sender on the thermostat, but that just sends info to the temp gauge.
Temp sensor, from my hazy memory is on the radiator, near the bottom.

driver_jasongroves, Mar 26, 8:38 pm

Hi there, found the sensor on the block below the Thermostat and other sensor.
Also found the choke set to half on by the previous owner brother keeping it half on with a hair clip bent to do so.
Took the hair clip out and hmmm, now it wont start.
The butterfly is completely shut.
Shall I invest in a rebuilt carburettor ornot.

driver_nomannz123, Mar 27, 8:55 pm