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1981 Seville Diesel, 1981 Seville V864
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5 Posts
Discussion Starter #1
1981 Seville 368 DFI

Car runs great except on a partially warm restart, then the idle speed fluctuates from 300 to 700 for about a minute. I have replaced the
ISC motor TPS, temp sensor, intake air temp sensor, egr, ignition module, and set everything up by the factory manual. If it stalls
enough times I get a check engine light, code 33. then it idles fine, but I get no cruise, or modulated displacement until I clear the code.

If anybody has any ideas, I welcome them

thanks
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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86,781 Posts
Re: unstable idle partially warm

Have you checked for a vacuum leak?
 

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Registered
1981 Seville Diesel, 1981 Seville V864
Joined
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5 Posts
Discussion Starter #3
Re: unstable idle partially warm

Yes, also have installed a rebuilt ecu
 

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Registered
1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
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6,737 Posts
Re: unstable idle partially warm

Verify fuel pressure is at spec. Could be too lean upon restart. There's a "sock" or pre filter attached to the bottom of the fuel level sender in the tank. If it's original that could be it.
 

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Registered
1981 Seville Diesel, 1981 Seville V864
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5 Posts
Discussion Starter #5
Re: unstable idle partially warm

Thanks for that idea, I can see where that could do it, certainly nothing else I have tried has made a bit of difference, although the car runs better and better (except for the idle issue)

I will let you know what I find
 

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Registered
1926 Model T street rod, 2000 Jaguar XJ8, 1999 Corvette.
Joined
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6,737 Posts
Re: unstable idle partially warm

Verify fuel pressure first. If it's below spec suspect the sock and/or the fuel pump itself.
 

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Registered
1981 Seville Diesel, 1981 Seville V864
Joined
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5 Posts
Discussion Starter #7
Re: unstable idle partially warm

Problem solved. Fuel pressure was on spec, changed fuel pump, sock and filter anyway

It was the Manifold Absolute Pressure Sensor. Also changed the baro sensor since I was in there. Cleaned up the Modulated displacement operation as well.
(as clean as it can be anyway)

Thanks for the ideas

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seems like it's always the LAST part I try before I can fix anything!
 
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