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» Hello Spec Miata Community » Spec Miata Archives » Garage 2002-2009 » idle speed issues

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Author Topic: idle speed issues
gwaronlawn
Member

Region: sfr
Year : 1991
Posts: 12
Status: Offline
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After the car warms up, the idle speed (which used to be correctly at 850rpm), is now at 1250. I adjusted it down and the idle adjust screw hits the hard stop when it is only at 950-1000 and won't go any lower.

Any ideas?

I checked the fault codes, and it is throwing a 14 - atmospheric pressure sensor. I doubt this is related, but have no idea.

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_ _________ _
Ryan Wellman

Mark de Regt Verified Driver Made Donation to Website
Veteran Member

Region: NWR/Oregon; ICSCC
Car #: 70
Year : 1991
Posts: 1111
Status: Offline
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Disconnect the idle speed control valve, and see if it makes any difference. If not, your ISCV is probably dead.

jcocke23 Verified Driver
Member

Region: NC
Car #: 86
Year : 1990
Posts: 135
Status: Offline
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I can't get mine below about 1050 RPM either. I bottom out the air screw, cleaned the TB numerous times, adjusted all the preload out of the linkage, and thats just where it sets. If I run stock timing, it idles correctly.

I've just accepted that thats the way its gonna be.

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Go Hokies!

gwaronlawn
Member

Region: sfr
Year : 1991
Posts: 12
Status: Offline
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my timing has been set at 16 and used to idle at 850 with the idle screw not even close to bottomed out. so something must have changed.

I'll try disconnecting the ISCV tonight and see if that does anything

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Ryan Wellman

backusm Verified Driver Made Donation to Website Series Champ
Member

Region: CenDiv
Car #: 94
Year : 90
Posts: 1319
Status: Offline
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vacuum leak. I had one that came from a cracked injector o-ring. Took forever to find. Also look at the crossover tube for the intake. They can rub on the pulley and get a small hole in the back that is almost impossible to see.

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Mike Backus
90 SM white #94

gwaronlawn
Member

Region: sfr
Year : 1991
Posts: 12
Status: Offline
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backusm, so how do you find such things. What's the best method? I've checked the vacuum lines (visually) and don't see anything. The tubes are all relatively new.

But what is the best method to diagnose a vacuum leak?

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Ryan Wellman

backusm Verified Driver Made Donation to Website Series Champ
Member

Region: CenDiv
Car #: 94
Year : 90
Posts: 1319
Status: Offline
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spray ether while car is running, wait for idle to rise. bingo

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Mike Backus
90 SM white #94

Dr.Dan Verified Driver Made Donation to Website
V8, nice! And good for you too!

Region: san francisco region
Car #: 39
Year : 90
Posts: 1800
Status: Offline
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Or, Spray N20 and just sit back and relax..:-)

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Daniel Mairani DDS...still here, just faster.
http://www.DanielMairanidds.com

gwaronlawn
Member

Region: sfr
Year : 1991
Posts: 12
Status: Offline
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Dan, is that how you got your Rebello working so well this year?
[Big Grin]

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_ _________ _
Ryan Wellman

   

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