Cadillac Owners Forum banner

1 - 15 of 15 Posts

·
Registered
Joined
·
11 Posts
Discussion Starter #1
Hello, I've been a lurker on these boards for awhile and have gained a wealth of knowledge from all the contributors..thank you.

I've searched threads and cant seem to find any solution to my problem.

My 02 cadillac deville dhs, just went over 100k miles.. So me and a buddy decided to do the plugs yesterday. After about 3 hrs of getting every thing in.. The car now runs very strange. When you hit the acceleration, It almost sounds like the engine is a harley motorcycle or something. Running idle she is fine, but once you give her gas.. you can hear the engine almost give a glass pack type sound from the engine. I cant seem to explain it, but the car just doesnt seem to run right.. There is no check engine light. I also ran toque pro app on my android, and no codes, or any errors show up.. So im baffled. I could swear that all the plugs are in correct..

Have any of you guys ever experienced this or know what it could be?


I though about taking a video of it, but it's really not loud enough to capture on video. It's not like a diesel engine or anything.. Doesnt seem to be misfiring.

Also, The plugs are acdelco Professional platinum, oem.

BTW: It ran fine before the new ones were put in. I was just trying to be maintenance minded and redo them since it just went over 100k.
 

·
Registered
2001 Seville STS, 1990 Seville (RIP), 1972 Sedan Deville
Joined
·
26,323 Posts
So is the problem with how it runs, or just a loud exhaust noise? If it's the noise, did you reconnect the rear A.I.R valve tube?

----------

Also, did you replace, or at least inspect and clean the plug boots? Use the correct AC Delco plugs?
 

·
Registered
Joined
·
11 Posts
Discussion Starter #3
Re: 2002 Cadillac deville dhs - New Plugs Issue/ Sounds like harly motor now- Please

yes, the problem is how it runs, and how it sounds.. It almost feels like it's in 3rd gear , kinda rides rough with acceperation. Just doesnt seem right. The rear air valve tube is in.. everything seems to be back in the way it was.. Could it be that the back 4 plugs may have not been tight enough? or a boot coil isnt in all the way? My buddy doesnt really know cadillacs and says its fine. I know my car and it defintely didnt drive or sound like that prior to the plug change. Im using ACDELCO. 41987. plug boots seemed fine.. The back plugs did have a bit of oil on the, but from what I read, that's not uncommon? If there was still oil inside the plug boots, would that be an issue, Maybe we didnt get all the oil wiped out?

----------

also, I havent drove on the freeway yet, because Im afraid that something is wrong.. Took her up to about 50 mph on the street and no check engine lights, etc.. just seems rough and loud ( like an old muscle car or something)..
 

·
Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
·
19,272 Posts
Re: 2002 Cadillac deville dhs - New Plugs Issue/ Sounds like harly motor now- Please

and you are sure you put all 8 new plugs in?
 

·
Registered
Joined
·
11 Posts
Discussion Starter #5
Re: 2002 Cadillac deville dhs - New Plugs Issue/ Sounds like harly motor now- Please

positive (and you are sure you put all 8 new plugs in?)
 

·
Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
Joined
·
68,458 Posts
Oil in plug boots is not usually a problem - but with 100K+ miles I would have replaced all of them.

Coil cassette ground springs - clean and "springy" ? Plugs torqued to 13 lb/ft with a tad of anti-seize on the first 3 threads. They come pregapped to .050" - did you check all the gaps for insurance ?

"Sounds like a Harley" - good ol' V-twin. If the engine exhaust and mechanical sound has changed from essentially "Cadillac quiet" then something is/has been done wrong. Back to the drawing board.
 

Attachments

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,783 Posts
Re: 2002 Cadillac deville dhs - New Plugs Issue/ Sounds like harly motor now- Please

The back plugs did have a bit of oil on the, but from what I read, that's not uncommon? If there was still oil inside the plug boots, would that be an issue, Maybe we didnt get all the oil wiped out?
No, that would not be the cause.

Based on your description in post #1 I agree with MC. Sounds like it might be exhaust gases being pumped back through the check valve and into the AIR pump. That would explain the muffled "glass pack type sound".
 

·
Registered
Joined
·
11 Posts
Discussion Starter #9
I'm going to take the plugs back out and check boots again most likely replace them.. if I try and clean the boots and cassette, what is the best method for cleaning? I appreciate all the advice and help here.. I just want to get her back to normal.. also, if the exhaust gasses are going back through the check valve and air pump what do I do to prevent that? I remember my buddy taking the house off to air pump thingy just to get to those 2 nuts under the pump valve thing with the metal coil tube.. but he put everything back.. my guess is something isn't tight enough.. weird thing is.. no check engine light
 

·
Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
·
19,272 Posts
could a plug got stripped and blown out???and that assembly is just holding it
---------------------
yup - it wouldn't be the first - and won't be the last -
 

·
Super Moderator
White Diamond '03 DHS (with DTS floor shift)
Joined
·
86,783 Posts
if the exhaust gasses are going back through the check valve and air pump what do I do to prevent that?
Make sure that the check valves are connected and working properly. That's what they are there for.
 

·
Registered
Joined
·
11 Posts
Discussion Starter #14
Rejoice Boys! We finally figured it out.. after going through everything again it was the air pump bracket and the intake wasn't flush .. so all that air was not going through thus making that sound.. She's back in action and riding like butter again.. Thanks for all the help. Happy Easter!
 
1 - 15 of 15 Posts
Top