1993 Miata will not idle

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10-01-2012, 06:37 PM
jrj512

1993 Miata will not idle

My car stopped idling all of the sudden and I can’t figure it out. Other than the idle issue, it runs fine. The engine is basically stock except for a header, exhaust, intake, and light-weight under-drive pulley. I have used this configuration since 2009.

Here is what I have done:

- Checked the plugs. Looked fine.
- Tested back-up set of wires.
- Used soapy water to test all of the vacuum lines, but I only tested the ends, not the rest of the lines. Hmmm. I will have to revisit the lines.
- Cleaned throttle-body.
- Tested air-valve using freezer and hair dryer.
- Replaced the PCV valve and grommet.
- Tested TPS with OHM meter.
- Tested secondary coils with OHM meter.
- Tested primary coils with OHM meter, but I did not get the expected results. Seems odd that it would be the ignition if the car runs fine otherwise. I was going to pull the ignition off a friend’s car and try it. Anyone think this is the cause?
- I do not have a CEL, but the there are two codes stored in there – 3 and 15. I replaced my O2 sensor a year ago. Even when it was malfunctioning, the engine did not act like this.

Any other ideas?
10-01-2012, 06:59 PM
Avarice

Maybe if you lost 20 or 30 lbs...
10-01-2012, 07:01 PM
motorollow

There is a write up in the garage section on the pointy board which covers idling issues and is specific to the 1.6.

I have issues where my idle will not come down immediately after coming to a stop. My idle will drop down to 1300-1400 rpm and after 5-10 seconds drops down to normal.
10-01-2012, 07:14 PM
tailchaser

This is the pointy board article of which he speaks... http://www.miata.net/garage/isc.html
10-01-2012, 07:48 PM
motorollow

Quote:

Originally Posted by tailchaser

This is the pointy board article of which he speaks... http://www.miata.net/garage/isc.html

Thanks TC, its not easy for me to put links in while on the phone (or maybe I just dont know how to do it!).
10-01-2012, 07:51 PM
jrj512

Quote:

Originally Posted by tailchaser

This is the pointy board article of which he speaks... http://www.miata.net/garage/isc.html

Thanks. I thought I already checked everything in this, but I will check again.
10-01-2012, 07:52 PM
jrj512

Quote:

Originally Posted by Avarice

Maybe if you lost 20 or 30 lbs...

Winning's not a problem. Just idling. ;)
10-01-2012, 07:55 PM
POS Racing

Quote:

Originally Posted by jrj512

Winning's not a problem. Just idling. ;)

Really I thought you got Hiromoto'd yesterday?? ::Rimshot:

IAC Tests out OK??
10-01-2012, 08:02 PM
SirHustlerEsq

Unplug the IAC and see what changes. My money is on the IAC.
10-01-2012, 08:06 PM
motorollow

Quote:

Originally Posted by mr brg

Unplug the IAC and see what changes. My money is on the IAC.

I think thats my problem too.
10-01-2012, 08:22 PM
jrj512

Quote:

Originally Posted by POS Racing

IAC Tests out OK??

Quote:

Originally Posted by mr brg

Unplug the IAC and see what changes. My money is on the IAC.

Quote:

Originally Posted by motorollow

I think thats my problem too.

I think I mistakenly bundled this when I tested my TPS, so I never tested it. I will have to try it. Thanks!
10-01-2012, 11:41 PM
EricJ

"stopped idling" - Does it die when you take your foot off the gas or run at above 750 RPM?

Does it change with Ground/Ten connected on the diagnostics port? If so, what does it do?

Is the idle control screw still there? Did it shake loose?
On my '94, some one had adjusted the idle via the stop screw on the throttle cable instead of the idle control screw at the top of the throttle body. After adjusting the stop screw it would die until the idle control screw was adjusted.
10-02-2012, 06:19 AM
jrj512

Quote:

Originally Posted by EricJ

"stopped idling" - Does it die when you take your foot off the gas or run at above 750 RPM?

It does down to a very low engine speed and then dies.

Quote:

Originally Posted by EricJ

Does it change with Ground/Ten connected on the diagnostics port? If so, what does it do?

It does not improve.

Quote:

Originally Posted by EricJ

Is the idle control screw still there? Did it shake loose?

Still there. I have not touched it, yet.
10-02-2012, 07:08 AM
ken o

As usual, I bet you have something stuffed in your exhaust hole.
10-02-2012, 07:44 AM
OZMDD

Quote:

Originally Posted by jrj512

Whining is not a problem. Just idling. ;)

Fixed!

I don't know much about the other tests mentioned, but I would definitely take a good look at the rest of the vacum hoses. Also, how are your grounding straps/battery terminals?

Let me know if you are going to work on it any evening this week; I'll be happy to come by and keep Leilane company. (or help you, I guess...)
10-02-2012, 07:51 AM
POS Racing

Does your car have the Racing Beat Sway Bar Brace Kit Hardware on it?

Not that that would have any bearing on your current problem but for some reason it just seems like a required question in the Miata Tech Section these days! ;-)

Did you fix it yet BTW??
10-02-2012, 07:58 AM
jrj512

Quote:

Originally Posted by POS Racing

Did you fix it yet BTW??

I will not be able to work on it again until Wednesday or Thursday.
10-02-2012, 10:50 AM
black roadster

Quote:

Originally Posted by POS Racing

Does your car have the Racing Beat Sway Bar Brace Kit Hardware on it?

Not that that would have any bearing on your current problem but for some reason it just seems like a required question in the Miata Tech Section these days! ;-)

http://4.bp.blogspot.com/_IF6Q-pCDIY...1g/shaddap.jpg
10-02-2012, 01:40 PM
gabkwong

[QUOTE=POS Racing;270853]Does your car have the Racing Beat Sway Bar Brace Kit Hardware on it?

Not that that would have any bearing on your current problem but for some reason it just seems like a required question in the Miata Tech Section these days! ;-)QUOTE]

There is an easy explanation/connection to this idle problem with the sway bar brace. It is the magnetic resonance, the lacking of, which diminished the force field and makes your coil pack not working and hence the idle problem! Easy! :-)
10-02-2012, 08:23 PM
EricJ

If nothing changes with ground/ten connected, then it's probably not the idle air control valve. IIRC the ECU controls it. That's why when adjusting the idle screw ground/ten is connected.

If opening the throttle, just a little, fixes the problem, could something be clogging the idle air bypass?
On my '99, I had to do the intake manifold clean for the EGR valve issue. When I did it, I also pulled off the throttle body and idle air control valve and cleaned it with throttle body cleaner. The throttle then closed properly, causing it to die at idle and requiring re-adjustment of the idle screw.
I just squirted throttle body cleaner in the idle air bypass. I read not to remove the idle screw completely. It's hard to get back in.
10-04-2012, 07:49 AM
jrj512

I took off the IAC and it OHM'd out just fine. I cleaned it out (did not seem too dirty) and put it back on. It appears to have fixed the issue. However...

I drove the car to work this morning. At one point, the issue started again. But then it stopped. I noticed that sometimes (just sometimes) when I have the car in gear with the clutch depressed (like at a stop light), the idle gets real low. Other times, no problem. I wonder if this is now a second issue with the clutch not fully disengaging? I have had occasional clutch slippage when launching at an AX that I did not previously have. I bled my slave a few months ago.
10-04-2012, 07:50 AM
sammm

When's the last time you changed the fuel filter?
10-04-2012, 08:33 AM
SirHustlerEsq

Dunk a bunch of rubbing alcohol into the IAC, shake, repeat, then try again. This is exactly what my green car did when it had a 1.6, and what my daily did with the 1994 t-body.
10-04-2012, 08:57 AM
jrj512

Quote:

Originally Posted by sammm

When's the last time you changed the fuel filter?

It was changed when I bought the car in 2006. I have put about 30K on it since then.

Quote:

Originally Posted by mr brg

Dunk a bunch of rubbing alcohol into the IAC, shake, repeat, then try again. This is exactly what my green car did when it had a 1.6, and what my daily did with the 1994 t-body.

Thanks, I'll give it a try. I might have some alcohol for myself in the process. ;)
10-08-2012, 11:32 AM
channelmaniac

Quote:

Originally Posted by jrj512

It was changed when I bought the car in 2006. I have put about 30K on it since then.

Thanks, I'll give it a try. I might have some alcohol for myself in the process. ;)

Not Rubbing Alcohol, unless your name is Dukakis...
10-08-2012, 11:46 AM
motorollow

I finally got my idle right yesterday. The new-to-me engine never idled correctly from installation. Anytime I came to stop the idle drop down to 1300 rpm and then 5 or so seconds later drop to 800. Bought some Berryman' s TB cleaner, thoroughly sprayed the TB, put the intake tube back on and fired it up. The idle was worse than before! It was idling at 1500 rpm and couldnt get it to go down. Got a paperclip and proceeded to reset the idle. Runs like a champ now!!