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Something German S, 69 Eldorado, 68 Impala, If I tell you the rest, well
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504 Posts
How's the plenum gasket between the intake and throttle body(Rubber Boot). See if it has a crack that might be your problem.
 

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2000 deville
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57 Posts
Discussion Starter #22
I will check the plenum tomorrow. The plenum was replaced about three years ago, before I did the coil packs plug boots and plugs. Thanks
 

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White Diamond '03 DHS (with DTS floor shift)
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87,194 Posts
If it was recently replaced it is probably just fine, besides, if it had a rip in it, you'd have a P0171 and/or P0174 code.
 

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2000 deville
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57 Posts
Discussion Starter #24
Plenum seems fine. I had an OBD II reading done and only P0300 came up. Again, this only kicks on after I reset codes and then about 5 miles of travel after a cold start.. I have a Car MD hand held reader and it shows P0300 as well. Last time I had this issue My Car MD gave me P0302 and P0307 etc, before I changed the coil packs and everything else..
 

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2003 DTS
'03 Deville DTS
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282 Posts
Just went through this myself with the P0300. Turned out to be a bad coil or rather a coil going bad, the misfires only happened after the engine got hot. Replaced the front coil cassette and everything's ducky again at my end. :)
 

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2000 deville
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57 Posts
Discussion Starter #26
Good to hear. Did it ever give you a specific code for the bad coil or just generic P0300?
 

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2000 deville
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57 Posts
Discussion Starter #28
So how did you know which one it was? I have replaced both my coil packs in the last three years. Simple to do, but did you just guess it was the front?
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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69,886 Posts
Remember - those coil cassettes, and their installed ICMs, are identical except for color.

DSCN0192.jpg
 

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2003 DTS
'03 Deville DTS
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282 Posts
So how did you know which one it was? I have replaced both my coil packs in the last three years. Simple to do, but did you just guess it was the front?
Just guessed on which one. Started with the grey one because it's the easiest to remove. Luckily for me that was the one that had a bad coil.
 

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2000 deville
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57 Posts
Discussion Starter #31
I did the TB clean and the IAC clean. Both were filthy and black, started hard and blew smoke, ran really good until it got warm and the P0300 code came up again on my OBII reader. What's next, as you know I replaced both coil packs, plugs, and boots in June 2017.
Thanks
 
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