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1990 sedan deville
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Discussion Starter #1
HI ALL NEW TO THE FORUM. I RECENTLY INHERITED A 1990 CADILLAC SEDAN DEVILLE IT IS A VERY LOW MILEAGE CAR AND PRETTY CLEAN. THE PROBLEM IS IT HAS WHAT SEEMS TO BE A MISS OR ROUGH RUNNING CONDITION THAT HAS GOTTEN WORSE RATHER RAPIDLY. I have checked all the plugs they seem clean and the only color to them is a light brown no sign of any carbon or fowling. I was wondering what to try next. any help would be appreciated. thanks in advance:hmm:
 

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White Diamond '03 DHS (with DTS floor shift)
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86,781 Posts
:welcome:

No need to shout. I edited it to bring the font down to normal size.

Might try checking the contacts on the cap & rotor. Mileage is too low for them to be worn, but stranger things have happened. Might need a new set of wires as well. At that age, plugs, wires, cap & rotor really can't hurt.

P.S.
Your caps button is stuck.
 

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1990 sedan deville
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6 Posts
Discussion Starter #3
sorry I didn't realize I was doing that until after it happened . I appreciate the reply .will check the cap :thumbsup:and rotor first
 

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2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
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Yeah, plugs, wires, cap and rotor, if original, should be considered ancient, and replaced.

That code can also be caused by faulty terminals at the ICM, a failing ICM, or a failing pickup coil.
 

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1990 sedan deville
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6 Posts
Discussion Starter #5
hi ranger I checked the cap and rotor the rotor and cap had corrosion on all points. the coil contact was rusty at the spring cleaned it up and it ran better till it got warm then it was intermittent I will try replacing the cap and rotor might as well get the plugs and wires also I put some seafoam in the gas tank and I am not sure how good the gas was in it so added some could this be part of it ? thanks again for your help.
 

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White Diamond '03 DHS (with DTS floor shift)
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Plugs, wires, cap & rotor would be a good idea. Seafoam snake oil, not so good. :tisk:
 

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1990 sedan deville
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6 Posts
Discussion Starter #8
Thanks to all for the heads up on snake oil seafoam .new cap and rotor noticed hole in bellows for cruise control looks like I have a vacuum leak any suggestions do I need the cruise.
 

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2011 Crown Vic LX, 2009 Chevy Malibu 2LT
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That's up to you. You could cap it off with no other repercussions outside of no working cruise. It wouldn't hurt anything else. Might be a good idea, if at least temporarily, to help your diagnostics processes.
 

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1990 sedan deville
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6 Posts
Discussion Starter #10
hi all . I replaced the plugs and wires was unbelievably smooth at idle sounds weird but when I opened the door to get in it seemed to sputter then when driving was fine for a few minutes and started running rough again . any suggestions I am wonderind if I have a loose ground or something else is loose.
 

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White Diamond '03 DHS (with DTS floor shift)
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86,781 Posts
If you suspect a ground, add a redundant ground from the negative battery cable to a good clean ground somewhere. A jumper cable will do. If that cures it, then the ground is bad.

Have you verified all the vacuum fittings are tight?
 

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1990 sedan deville
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Discussion Starter #12
Hi all , haven't had much time for the caddy took it for a ten minute drive ran really good to the store after sitting for 15 20 minutes ran rough coming home will check out the ground today my wifes car broke down fixing it.
 
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