Fabo979

1996 Cadillac Deville High Idle

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I have a 1996 deville that idle highs at around 2200-3000 RPM when sitting park and when it is in drive it can reach about 30 mph without me pressing the gas. I've changed the following parts and still doing the same thing. vehicle does not misfire or idle rough and starts up immediately. I am stumped.

-changed TPS

-changed MAF SENSOR

-changed IDLE AIR CONTROL SENSOR

-changed INTAKE MANIFOLD GASKETS

-changed EVAP PURGE SOLENOID

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Have you checked for vacuum leaks.  I'm just a 'shade-tree' and will yield to our real techs out there.


Chuck

'17 XT5, '04 Bravada........but still lusting for that '69 Z-28

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Did you replace the throttle body gasket...?

Sounds silly but a important question.

Could be a vacuum leak but would rather wait for the response to my question


GM FAN FOREVER

Nice, clean, luxury= fine automobile

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disconnect the mass air flow sensor and try running the cart. I suspect you have a wiring issue to the iac or a bad pcm

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16 hours ago, cdgrinci said:

Have you checked for vacuum leaks.  I'm just a 'shade-tree' and will yield to our real techs out there.

all my hoses looked good. but since i changed my intake gaskets i can hear a leak around the throttle body but i can't pinpoint it.

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9 hours ago, rockfangd said:

Did you replace the throttle body gasket...?

Sounds silly but a important question.

Could be a vacuum leak but would rather wait for the response to my question

no i have not, that will probably be the next task i will try. Thanks

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1 hour ago, barczy01 said:

disconnect the mass air flow sensor and try running the cart. I suspect you have a wiring issue to the iac or a bad pcm

 i will try this today. when i disconnect it and run it, what should i be looking for?

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Ok If you have not replaced it then it is not likely the cause.

You said you replaced the IAC valve. Did the problem get better, worse, or same?

Knowing the codes before anything occurred  would be great. Were they pulled?

Disconnect the battery for a little bit. Reconnect it. Start the engine, put in gear and hold your foot on brake for 1 minute.

Shut down

Restart engine turning on all loads, AC, etc... Put in gear and do the same as above for 1 minute.

That should relearn proper idle. If it does not then there is another issue.

Check all vacuum lines to the intake.

Knowing your IAC counts would be great as well but you would need a scantool to read that


GM FAN FOREVER

Nice, clean, luxury= fine automobile

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11 hours ago, rockfangd said:

Ok If you have not replaced it then it is not likely the cause.

You said you replaced the IAC valve. Did the problem get better, worse, or same?

Knowing the codes before anything occurred  would be great. Were they pulled?

Disconnect the battery for a little bit. Reconnect it. Start the engine, put in gear and hold your foot on brake for 1 minute.

Shut down

Restart engine turning on all loads, AC, etc... Put in gear and do the same as above for 1 minute.

That should relearn proper idle. If it does not then there is another issue.

Check all vacuum lines to the intake.

Knowing your IAC counts would be great as well but you would need a scantool to read that

when i changed the IAC valve, the problem stayed the same.  all the coded that were pulled led me to change all the parts i mentioned already and now there no more codes. i  will try to relearn the proper idle today when i get off work. Thanks for the tip.

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