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98 Concours, 2004 Deville DTS
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Discussion Starter · #1 · (Edited)
2004 Deville, I assume it’s probably a coil causing the issue on the #1 cylinder missing (of course the one in the back) but I would like to swap the coil out with another cylinder to verify that is the problem. It looks like I have to remove the air pump check valve just to get to the coil but do I have to put the valve back together after switching coils for testing purposes? Seems like a major pain, any suggestions? Oh and the 2004 uses the bank of coils and not the cassettes (hope that makes sense).
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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73,418 Posts
murph, unfortunately you'll need to pull the AIR valve again.

Harry, Nope. At the start of the "2004" model year (July 2003) they phased in individual COP assemblies.

Here's the first generation for the 2004 Seville Northstar. The assembly changed again for ? 2005 ? FWD Northstar vehicles -

598759
 

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70 Deville 78 Seville 92 Deville 03 Deville
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That check valve doesn't need to be completely removed. You can remove a couple bolts or nuts and move it to the side to gain clearance.
 

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98 Concours, 2004 Deville DTS
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223 Posts
Discussion Starter · #5 ·
I thought about trying to move it to the side but it seems the bracket would still be in the way? Also (correct me if I am wrong ) but it seems that Sub has mentioned that the flex pipe gets brittle and might not be a good idea to bend it (it only has 50,000 miles on it so maybe I would be ok :) ? Since this is the #1 plug I thought about cutting that plastic cover and leave the valve in place, then later if i wanted to replace the cover once the debugging is complete i could (keep it original).

Thanks so much for the info and any additional would be apricated.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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20,988 Posts
2004 Deville, I assume it’s probably a coil causing the issue on the #1 cylinder missing (of course the one in the back) but I would like to swap the coil out with another cylinder to verify that is the problem. It looks like I have to remove the air pump check valve just to get to the coil but do I have to put the valve back together after switching coils for testing purposes? Seems like a major pain, any suggestions? Oh and the 2004 uses the bank of coils and not the cassettes (hope that makes sense).
====================
if it was me - and I suspected a faulty coil on #1 -
I would swap both coils -
put the "known good" front (left) coil on the rear (right)
and the questionable rear (right) on the front (left) -
button it all up -
IF the coil IS bad the misfire will follow the coil -
and it's now on the "easy" side to replace -
 

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98 Concours, 2004 Deville DTS
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223 Posts
Discussion Starter · #7 ·
I guess I am going to attempt to remove the check valve but can't find much info on best way to do it. Is it best to remove the 2 bolts on the end of the pipe (by the manifold) and then the 3 bolts (I think 3) from the bracket and just slide it out leaving the valve still mounted to the bracket? Also should this all be done from the top or are some of the bolts reached from underneath?
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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73,418 Posts
You can do it from the top with stretching and magic words, engine cold. Remove the 10mm manifold flange nuts, then unbolt the bracket.
 

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98 Concours, 2004 Deville DTS
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223 Posts
Discussion Starter · #9 ·
Valve is out, it came out easier then I thought, took me about an hour (yes I am slow) with no loss of bolts/nuts as of yet. I expected everything to be froze up since it is so close to the exhaust but all the nuts and bolts came out out easy (almost too easy). Since its hard to reach the connection at the manifold is it safe to assume no real cleaning or gasket replacement is necessary (they look OK, I might take the wire wheel on the valve side although it looks pretty clean)?

====================
if it was me - and I suspected a faulty coil on #1 -
I would swap both coils -
put the "known good" front (left) coil on the rear (right)
and the questionable rear (right) on the front (left) -
button it all up -
IF the coil IS bad the misfire will follow the coil -
and it's now on the "easy" side to replace -
This is exactly what I was planning on doing but so far every coil (front bank) I have tried to unplug the electrical connection has broken (I guess from the heat or maybe they were already broken). Since I don't want to pull that valve again if I can help it I just bought the whole assembly of coils for the rear and will be putting new plugs in as well and hopefully can salvage enough parts to fix the front bank, if not I will order the front one as well.

Thanks!
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
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20,988 Posts
Valve is out, it came out easier then I thought, took me about an hour (yes I am slow) with no loss of bolts/nuts as of yet. I expected everything to be froze up since it is so close to the exhaust but all the nuts and bolts came out out easy (almost too easy). Since its hard to reach the connection at the manifold is it safe to assume no real cleaning or gasket replacement is necessary (they look OK, I might take the wire wheel on the valve side although it looks pretty clean)?



This is exactly what I was planning on doing but so far every coil (front bank) I have tried to unplug the electrical connection has broken (I guess from the heat or maybe they were already broken). Since I don't want to pull that valve again if I can help it I just bought the whole assembly of coils for the rear and will be putting new plugs in as well and hopefully can salvage enough parts to fix the front bank, if not I will order the front one as well.

Thanks!
=======================
there were TWO DESIGNS for the coils -

the ORIGINAL DESIGN had VERTICAL electrical connectors -
the individual coils are NOT replaceable -

the UPDATED DESIGN has HORIZONTAL electrical connectors -
599011

these individual injectors ARE replaceable -
 

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98 Concours, 2004 Deville DTS
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223 Posts
Discussion Starter · #11 ·
This work is complete, thought I would add some comments. First the valve over the cam cover was not nearly as big of a deal as I thought it would be. Put down some kind of pad over the radiator support for your knees and climb up on it. I would suggest buying a 10 mm magnetic socket (7 bucks on Amazon with next day shipping). I did not clean or replace the gasket to the manifold and it seems to be working just fine. I did forget to put the plastic coil cover back on (debating if I should remove the valve again and install the cover).

On to the coil replacement. I took a bunch of time getting a tech2win (tech 2 on windows) working so I could figure out which coil was causing a problem (turned out to be mostly coil 1 and somewhat coil 2). That being said I am not really sure the coils were the problem, I think maybe the electrical connectors where old and brittle and were the real culprit. Anyway after spending all that time to figure out exactly which coil/connector was the problem I ended up replacing both the front and rear coil assemblies (all 8 coils which of course came with new wiring harness, this is after attempting to replace just the bad coils :). Moral of this story is that in this one case parts replacement instead of diagnosis would have saved me a bunch of time. LOL

If anyone knows where to get a new wiring harness for the coils at a reasonable price please let me know and I will see if I can get my old coil assemblies working for a backup. So far all I can find are just the connectors to splice in for an unreasonable price, would really rather have the whole assembly.

Hope this helps someone else and thanks for the help!
 
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