[Bigjack]

Hey I have an 02 DTS that recently just started getting the rough idle syndrome was checking here and saw the plenum issue that others were having and was wondering how do you go about checking the plenum as well as what codes with this issue pull up. Yesterday pcm 0410 & 0300 came up when i ran self diagnostic. Any hlp would be much appreciated. Thanks

 

[Submariner409]

Remove the engine beauty cover and start the car in P. Shoot a tad of choke cleaner or starter fluid at the base of the hose clamp between the throttlebody and intake manifold inlet. The hose clamp in there at #2 in the diagram - any idle speed change = cracked plenum.

Intake manifold bolt torque is 89 in/lb - 5.5 ft/lb. Not much. careful. New plenum is $40 or so, dealer only - call Luke at Lindsay Cadillac, Parts, M-F, 9-5 EDT. >>>>> over there

 

[Bigjack]

Remove the engine beauty cover and start the car in P. Shoot a tad of choke cleaner or starter fluid at the base of the hose clamp between the throttlebody and intake manifold inlet. The hose clamp in there at #2 in the diagram - any idle speed change = cracked plenum.

Intake manifold bolt torque is 89 in/lb - 5.5 ft/lb. Not much. careful. New plenum is $40 or so, dealer only - call Luke at Lindsay Cadillac, Parts, M-F, 9-5 EDT. >>>>> over there

thanks

 

[Submariner409]

P0410 is secondary A.I.R. system and might have something to do with the air valves to the exhaust manifolds, but nothing to do with intake or plenum problems - the P0300 is "miss detected".

Double check your codes again - don't reset them - and make sure you log which is Current or History.

 

[sharpcar69]

you got a misfire thats causing the other code,chances are its gonna be a coil pack,i have had my fair share of caddys 2000 and up and front coils have been somewhat of the problem,also when was the last time you changed your plugs if it was recent and you put something else instead of original that can do it to you also po300.i hope its not your coil pack they are eeexpensive.also if your leaking oil thru valve cover spark plug gromets that can cause a misfire as well,and a bad injector too,at the least injectors you can check with car running un pluging them one by one to see which clyinder has misfire and you can swap them around to make sure its a injector.as for the coil pack its a little more technical cause since its a really big block thing proper diagnostic would be only way before you go out and spend big bucks on coil packs...good luck

 

[Bigjack]

Thanks for all the help turned out to be the plenum was the cause of all the trouble. Took care of it and now were running like we're supposed to thanks again eveybody.

 

[DIS DTS]

Remove the engine beauty cover and start the car in P. Shoot a tad of choke cleaner or starter fluid at the base of the hose clamp between the throttlebody and intake manifold inlet. The hose clamp in there at #2 in the diagram - any idle speed change = cracked plenum.

Intake manifold bolt torque is 89 in/lb - 5.5 ft/lb. Not much. careful. New plenum is $40 or so, dealer only - call Luke at Lindsay Cadillac, Parts, M-F, 9-5 EDT. >>>>> over there

Are you aware of a link that shows how to replace the intake plenum boot?

 

[Submariner409]

Go to Northstar Performance (Engines) and do some snooping around for pertinent threads - many, many, and some with diagrams and pictures.

Click on the little picture album icon under my login name. On Page 1 of that album there are 2 diagrams - one of the fuel rail being lifted and another of the intake manifold being removed - the plenum is #2 in that drawing.

Make sure that you follow the torque settings posted earlier in here - too much and the manifold cracks.

 

[DIS DTS]

Go to Northstar Performance (Engines) and do some snooping around for pertinent threads - many, many, and some with diagrams and pictures.

Click on the little picture album icon under my login name. On Page 1 of that album there are 2 diagrams - one of the fuel rail being lifted and another of the intake manifold being removed - the plenum is #2 in that drawing.

Make sure that you follow the torque settings posted earlier in here - too much and the manifold cracks.

Thank you for responding. I went through 10 pages of related threads. There was a lot of good info. But not a step by step. Please let me know if anyone has a link to a step by step, possibly w/pics on replacing the plenum gasket on an '03 DTS.

 

[Submariner409]

To the best of my knowledge, there are no literal step-by-step threads on replacing the plenum on a 2000+ Northstar. That's the realm of a GM Helm Factory Service Manual or a subscription to www.alldatadiy.com.

You remove the beauty cover, disconnect the fuel rail and FPR vacuum line, remove the fuel rail, loosen the plenum clamp, pull the manifold bolts, remove any vacuum/supply lines necessary, lift the manifold, unbolt the plenum from the throttlebody, clean the throttlebody, (forget trying to clean out the oily deposits in the manifold), check the starter cable connections, install the plenum, use new intake gaskets, oil the lower fuel injector O-rings, and put it all back the way it was.

Here's what you're after............

 

[DIS DTS]

Thank you for taking the time to lay that out. You've helped me in the past as you have helped countless others.

 

[DIS DTS]

Here is a step by step I found.
http://www.justanswer.com/questions/20f8d-2001-cadillac-deville-dhs-leak

 

[holgatelbi]

This copy of a post was my tutorial on plenum replacement - was right on

PLENUM BOOT REPLACEMENT By MRSVPITBULLS



1) Removed gas cap

2) Pop hood remove Top cover and bleed off pressure from fuel rail pressure relief valve

3) Take off top of air box and air tube closest to tb, unplug maf plug

4) Just loosen the 10mm nut that holds fuel lines down and undo lines from the black clip on top

5) Unclamp the top line on the coolant jug (a little might come out) Lay it to the side

6) In front just unhook one vacume line and unplug the plug going into coil pack

7) In back just unhook the vacume lines that are in the way (I think it was 4 or 5 of them) and unplug the plug going to that coil pack

8) Take the 4 10mm bolts out that hold the fuel rails down

9) Carefully pull up on the fuel rails evenly, they will all pop out together, pull them straight up together you'll have to wigle it around a little but you can get enuff room to work

10) Take the 10 10mm bolts out of the manifold

11) Loosen the plenum bolt (The strap clamp) there are also 3 10mm bolts that hols the plenum in. You'll see them from driver side, pretty easy to get to

12) Hold the fuel rails up out of the way and start from passanger side and lift the manifold up and out

13) Turn manifold over replace all 8 Blue gaskets (most local parts stores have these $15-$20 for a set of 8 )

14) Take off old plenum ( I used a big screwdriver and pryed up around the sides)

15) Put your $30 new plenum on (the same way the old one came off)

16) I took my shop vac and vacumed out everything so nothing would fall in engine, then just wiped it down with old shirt rag

17) Hold fuel rails back up and drop the manifold back into its home

18) Reasemble everything you just did. On the manifold bolts just start in the middle and work your way around, don't tighten till there all hand tight.

Thats pretty much it. Of course inspect everything as you go.

When i did this job all 10 of my manifold bolts were loose like all of them were just hand tight. I thought that was crazy..