1981 Cadillac Deville code 30

HANK4485

MEMBER
1981 CADILLAC DEVILLE
100,000 MILES

Intermittent code 30, code will not clear with ECC panel nor disconnecting battery
for 10 seconds. If I disconnect battery, come back to it in a day or so, the ISC plunger will come out to fast idle, as it warms up, retracts to Idle. As long as I don't turn key off, ECM commands ISC fine(A/C etc.). Turn key off and ISC plunger comes out to fast idle and stays there. Replaced complete engine wiring harness, ISC motor, 2 ECM's. Adjusted min. Idle, max. Idle, and TPS. Any ideas? Thanks
Hank.

3 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

The isc should fully extend engine off. Thats normal.

What did you set the tps at? What did you set the base idle at?

Did you use a new isc? Gears failing inside were very common. Re built hundreds of them for this reason.

Roy

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Sunday, August 4th, 2013 AT 12:38 AM

HANK4485

MEMBER
3 POSTS

TPS 50, min idle 375, max idle 1500. New ISC motor.
At times, no pattern, I can get code to clear with ECC panel, if I start car with out turning ignition off, ECM controls ISC motor, with and with out a/c on, turn ignition off, then back on, idle stays high. Thanks for your help.
Hank

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Sunday, August 4th, 2013 AT 10:16 AM

HANK4485

MEMBER
3 POSTS

Hi, also when I disconnect battery and leave it set for days, on the first start the ECM commands the ISC and it works fine until the ignition is turned off then restarted. Any help would be use full thank you.
Hank

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Wednesday, August 7th, 2013 AT 8:30 AM