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Cadillac seville sts 1999
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9 Posts
Discussion Starter #1
Hey guys trying to diagnose a misfire problem with my 99 sts 109K miles which
of course seems to only have trouble more than 500 mi from home!!!
Called a Chevy dealer told them the car was misfiring so I get an appointment bring it in they give me a run around for a couple days then when I go to pick it up the service manager tells me that it's misfiring and it could be a problem with the ignition system, fuel system, or exhaust......:want: thanks alot victory chevy kitty hawk NC...
anyway they replace the wires that didnt help...but they didnt replace the plugs so im thinking i may as well start there.
I thought I may swap out the crankshaft pos sensors next.
Anyone with any ideas?
The problem seems to occasionally stop for a little while sometimes then come back cant see anything like temp that corresponds to it coming and going. The one thing I got from the dealer was that it was multiple cylinders misfiring and supposedly only cyl #1after they replaced the wires.

Also does anyone know if I can pull the engine codes Ive seen some cadillacs that can get the codes from the driver info computer but i dont have the misfiring code coming up just the blinking service engine light
Thanks guys i will keep posted as I work my way through it!
 

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Registered
1996 Deville (sold), 2000 Mustang GT
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1,300 Posts
Yea, you can pull the codes yourself, just do a search on the forum, i forget exactly how. If they replaced the plug wires your next stop would be the plugs, if they are original there's a really good chance they need to be replaced. Getting to the four in the back isn't too much fun. Usually the crank position sensors won't cause a misfire, just stalling and they will throw a code. I'd stick with the plugs, if it doesn't cure it, maybe the coil packs are bad. Also check your ground cables and battery terminals.
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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86,994 Posts
The only thing I can add to what Misfit said is stick with A/C Delco plugs. The blinking SES light indicates a severe misfire detected. My money it on the plugs.

Oh yeah, I think on the '99 you press the OFF & INFO UP buttons for the DTC's. There is a "sticky" in the Tech Tips section.
 

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Cadillac seville sts 1999
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9 Posts
Discussion Starter #4
THANKS GUYS! Well turns out my low opinion of the dealer who checked it out got a little lower today... started with the fuel injectors they supposedly checked and it they had chunks of buildup almost like sand all over the top so i cleaned that off and when I went to put cylinder 1 back in I couldnt so I poked around in it a bit and voila an extra o ring was jammed up inside guess that explains the 8.99$ o-ring kit the dealer added to the bill! So I replaced the plugs actually easier on this than most cars I get to the last cylinder #6 behind the coil pack and found the spark plug wire wasnt connected at all just hanging behined the motor! So good news is the spark plugs and actually connecting wires to them did the trick cars running great again! Oh and I used Denso double platinums I would have stuck with the a/c plugs but I didnt read that post in time.
Thanks for all the input guys great forum cant believe it was such an easy fix
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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69,131 Posts
:thumbsup: Believe it or not, the 41-987 and lower 41 series AC plugs are "Made in Japan". DENSO, AC, allee samee.........
 

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1996 Deville (sold), 2000 Mustang GT
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1,300 Posts
Thats why I try to do everything I possibly can myself when my car needs it, dealerships are an overpriced, underqualified, joke.
 
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