pose_etc

2001 Seville sts high idle and 0507 code.

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Hi there.

As the title states, this car has a high idle and when I revved it it stuck at around 3k rpm and gradually came down after shutting the engine off and restarting it and eventually drove it for about 10 mi Tues where it idled at around 2k rpm.

This is extremely frustrating since I THOUGHT I fixed this already.

I have already replaced the IAC twice and the TPS.  Please please please give me some insight before I give this car a Viking Funeral.

Thanks in advance.

Pose

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Have your checked the throttle body for carbon build-up at the butterfly; could it be a physical hang up from an obstruction?  And have you checked for vacuum leak?

Edited by cdgrinci

Chuck

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

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Been there done that.

It sucks.

Were the replacement IAC and TPS oem?

I speak from experience when I say aftermarket ones just dont work properly


GM FAN FOREVER

Nice, clean, luxury= fine automobile

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I'm thinking more on the vacuum side. I had a new engine swapped in last summer since the original had a cracked block. I was told the pcv tubes had to be "Frankensteined" together.  That sounds like a good place to start as well as an intake coupler.  I have a good shop that can check this out and fix it properly or better than original.  My best bet is to go that direction.  I'm planning to have them just go through and tie up any loose ends from the swap.

At that point I can see if the parts are any good.

Edited by pose_etc
Adding info

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Just started and ran the car for around 10 minutes.  It idled around 1k rpm and as it warmed up it took longer and longer to come down to idle.  Seems to support my vacuum leak theory.

Any thoughts?

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The #1 culprit I would think of would be the coupler between the TB and the intake. Very common. Fails on the bottom


GM FAN FOREVER

Nice, clean, luxury= fine automobile

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I concur with the vacuum leak possibility. Easy to find with a can of carb spray.  Spay on the vacuum lines  one at a time. If the RPMS suddenly rise, you found the leak. You can also use a squirt bottle of water, only the RPM will stumble when you find the leak. I made a smoke machine from a soldering iron, a  clear glass mayonnaise jar holding a sock soaked with baby oil, and clear aquarium tubing. Woks great. Found two leaks last year on my 95 Seville.     

 

Edited by CampoCougar

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As @rockfangd noted, the rubber plenum will develop a hole on the bottom where unmetered air leaks raising the idle.   The combustion/EGR condensate muck collects and sits on the bottom eventually deteriorating the rubber.  

You might spray a non flammable solution in the area and see if the idle changes.   The P0507 might have set if the system thinks the IAC is hanging open and raising the idle.  

Is that the only code you are getting?   I would think you might see lean codes P0171 and P0174 indicating a lean mixture on both banks with a plenum vacuum leak.   It is odd that you aren't getting lean codes @rockfangd what do you think?

 P0507 Cadillac Description. The stepper motor drives a valve pintle which protrudes into a passage that bypasses the throttle plates. The PCM commands the IAC valve pintle to extend to decrease the idle speed. The bypass air flow is reduced and the idle speed decreases as the pintle approaches its seat.

Have you tried deleting the P0507 code after you replaced the IAC valve? Try deleting the code and see if it comes back.   Is the P0507 code current or history?  When you removed the IAC did you clean the seat and port in the throttle body?   I doubt the port is clogged, that would lower the idle, but if something were on the seat keeping the IAC from closing, the idle would be high.  Remove the IAC and take a good look at the seat and connector.

 


Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Funny thing is sometimes I see the lean both banks, sometimes I don't. You would think there would be.

 


GM FAN FOREVER

Nice, clean, luxury= fine automobile

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1 hour ago, rockfangd said:

Funny thing is sometimes I see the lean both banks, sometimes I don't. You would think there would be.

 

It is possible the leak is so small it impacts the idle but not the air/fuel ratio and the system looks to the IAC as a result.  Thx


Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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The only code is the 0507. It comes up as the car warms up.  It's probably the coupler from what you're describing. I should be receiving one today, as a matter of fact.

I usually delete the code asap but it eventually comes back.

Thanks for all your input.  I think I'll be taking it to my mechanic pretty soon since there are a couple other things I need him to look at since the engine swap.

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54 minutes ago, pose_etc said:

The only code is the 0507. It comes up as the car warms up.  It's probably the coupler from what you're describing. I should be receiving one today, as a matter of fact.

I usually delete the code asap but it eventually comes back.

Thanks for all your input.  I think I'll be taking it to my mechanic pretty soon since there are a couple other things I need him to look at since the engine swap.

Let us know how this turns out, thanks


Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Okay, as insurance on this idle situation I'm going to purchase an OE IAC valve.  Could Delphi be trusted or just go with AC Delco?

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Delphi should be ok. Prefer Delco. But not even sure where they come from anymore.

Did you replace the coupler yet?


GM FAN FOREVER

Nice, clean, luxury= fine automobile

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Not yet. Thought I'd do this before I get the coupler done.  I thought it would save me a few bucks since I can get the Delphi one from Rock auto and change it myself at a reasonable price vs what a shop would charge for such a simple job.

Also thought I'd clean all the passages and throttle body while I was at it.

Edited by pose_etc
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EUREKA!!!!! I FOUND THE PROBLEM!!

The throttle cable bracket was putting too much tension on the cruise control trolling and throttle cables.  A couple taps with a hammer to give it some slack and it idles and revs properly.

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So the bracket that the cables attach to was bent?

I guess thats possible. Glad you figured it out. Must have gotten bent somehow


GM FAN FOREVER

Nice, clean, luxury= fine automobile

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Either bent or the wrong bracket.  The engine came from a DTS, so I don't know if the brackets were different or what.  Doesn't matter, just glad I found it and it didn't cost anything.

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