Sign in to follow this  
Luke

2006 DTS rough idle

Recommended Posts

I posted this in a model specific forum with little response.

My 2006 DTS has 165,000 miles. I've since purchased a 2008 DTS Performance Ultra Luxury but still love my 2006 and would like to get it going again.

Sometime a couple of years ago, my DTS started occasionally dinging and showing SERVICE TRACTION CONTROL & SERVICE STABILITRAK. Over time, it became more and more frequent. The car had always had a slip in the transmission. I assumed the two were related. So, I had a used transmission with 24k miles installed.

Not only did the transmission not fix the problem, it is worse. Still get the dinging and messages and now the engine idles rough. In all my searching online, and all the different recommended repairs, NEW parts the car has had:

*intake gaskets and plenum

*MAF sensor

*MAP sensor

*throttle body and gasket

*evap purge solenoid

*gas cap

*EGR valve and gasket

*valve cover gaskets

*alternator (bad alternator was causing the engine to rev and I almost rear-ended someone)

I took the intake manifold off last night to inspect for cracks and found nothing. There just doesn't seem to actually be a vacuum leak. I have blocked off every vacuum connection to the engine and none have improved the problems. Whatever is wrong, it's fooling it into thinking it's a vacuum leak.

I even took the car to Sewell Cadillac in Dallas (very poor dealership). They found nothing wrong. Charged me $500 for a new EGR gasket and to charge the battery. I fought it and got a full refund.

I have searched everywhere more for a solution. Ideas I have found online include bad O2 sensors, bad coils, bad spark plugs, bad/clogged fuel pump, bad injectors, etc. Spark plugs only have maybe 20,000 miles on them.

These codes and messages are not uncommon on 2005 and older Northstars due to the intake plenum tearing but seem very rare on 2006+ cars.

I have no idea where to go from here. Does anyone have any idea? Anyone experience this on a 2006+ DTS and found a solution?

Share this post


Link to post
Share on other sites

The intake, plugs, alternator and such will not likely have anything to do with suspension messages. Look to the wheel speed sensors, height sensors, and EBTCM connector - all these are usually wiring harness issues.

I notice that you do not have a list of OBD codes. Autozone and others will run the codes for you. Be sure that you get the suspension codes, not just the emissions codes, because the suspension codes are what tells you what causes traction control and Stabilitrak messages.

I don't know what you mean by "dinging." If this is the alarm chime, it's an alert that you have a console message.


CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Share this post


Link to post
Share on other sites

I forgot the codes. It has only showed P0171 and P0174. When I reset these codes, traction and stabilitrak codes go away.

It has had new front hubs/bearings/wheel speed sensors. All wheel speed sensors are running within spec. It does not set any suspension or brake codes.

It is common for them to show the SERVICE TRACTION CONTROL and SERVICE STABILITRAK when these lean codes are set. Northstars thru 2005 would do the same thing when the intake plenum leaked. All signs point toward a vacuum leak. But there just doesn't seem to be a vacuum leak.

Somewhere there is some phantom sensor that is causing it to run lean or perhaps a coil or fuel pump. It's a mystery!

Edited by Luke

Share this post


Link to post
Share on other sites

It's hard to diagnosis a car without a scanner and getting actual readings. Could be an oxygen sensor or an actual engine internal valve sealing problem. Diagnosis is 80% of the battle! Sorry about the bad luck Luke, you definitely covered your bases.

Share this post


Link to post
Share on other sites

My guess is that it's unlikely it's a valve problem. If that was the case, I am guessing that it would be P0171 OR P0174 rather than both. It is always both codes. But, just in case, I am going to put some Marvel Mystery Oil in the oil to clean the engine out. Maybe something is sticky that it'll free up.

Honestly, I don't have a lot invested in parts. I watch ebay closely and snag new OEM parts for cheap before buying them.

I am going to get a fuel pressure gauge this weekend and try to rule out the fuel pump. I'll probably go ahead and change spark plugs to and rule that out.

At this point, it's an extra car so I am not in a huge hurry to get it going. Although I'll likely start driving it again daily when it's fixed, I am able to take my time and really figure it out.

Edited by Luke

Share this post


Link to post
Share on other sites

Excuse me, but I don't see how lean mixture codes can be related to suspension messages, other than through low battery voltage or a break in the wiring harness, both of which seem to be ruled out.

To be sure, you might check your battery cables.

If you are getting lean codes on both banks, it's probably a vacuum leak like a break in the PCV valve hose, a loose or missing oil filler cap or oil dipstick, or a missing or cracked vacuum hose on the throttle body. Bad throttle body buffer neoprene can cause vacuum leaks and lean codes too.

Most code readers don't see suspension codes.


CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Share this post


Link to post
Share on other sites

If you search for DeVille, SERVICE TRACTION COBTROL, and P0171/P0174, you'll find that it's quite common to have the suspension/brake messages show up due to vacuum leaks. They never do set suspension codes in these cases. The 00-05 Northstar had an intake plenum design that would eventually tear and cause the messages. Why Cadillac programmed it so these messages show up when lean mixture codes are set, I have no idea. But that's just the way it is.

A mechanic friend has a Snapon computer that cost thousands and it'll read any code the car can produce. It has set no suspension or brake codes. He has used it to watch what each wheel speed sensor is doing as I drive and all were correct. Even when the messages started. He has used it to watch a bunch of different parameters involving brakes and suspension on the car and has found nothing wrong. The problem is with the lean condition.

I believe what is causing my problem is a crack in the PCV tube sticking out inside the end of the manifold. This requires a new intake manifold since the tube isn't removable. A new one is $500+. I may fill the end with expanding foam insulation to see if it'll fix it temporarily and buy a new intake manifold later. Used ones are cheaper but may have the same problem.

Edited by Luke

Share this post


Link to post
Share on other sites

So, the throwing of suspension messages for two model years is a software bug. Amazing. But I guess it's true, because ... you can't make this stuff up.

Does anyone have a picture from the 2006 FSM showing the PCV tube? It may not be sold separately by GM parts but there has got to be a way to change it, or fix it, like a miniature welder.


CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Share this post


Link to post
Share on other sites

Actually, from what I understand, it's not a software bug. It's programmed that way. Northstars 2000+ do this. At least the front wheel drive ones as far as I know. It's rather common on the 2000-2005 models when the intake plenum eventually develops a tear and causes a vacuum leak. It's not so common on 2006+ models since the plenum was redesigned. I guess I just got lucky.

I'm going to replace the plastic tube that runs from that tube in the manifold to the valve cover for good measure. But the tube that's part of the intake manifold is molded in. It's plastic and tough to get to. Not sure how easy it would be to weld plastic. We'll see how long the spray foam insulation stuff will hold. I got a can today. I'll try it out tomorrow and report back how it worked.

Edited by Luke

Share this post


Link to post
Share on other sites

I believe traction control puts the engine in a kind of limp / reduced power mode. With the engine running poorly, it probably is reporting it will not be able to downgrade the engine performance anymore to support these features - and this is what sets the code. Kind of like having a fuel cap code set, and remote starts are denied.

Share this post


Link to post
Share on other sites

It always pays to go check for service bulletins before doing anything....sometimes you get lucky. I guess you need to go check your VIN #.

#06-06-04-023: LD8, L37 Service Engine Soon (SES) Light Illuminated or Traction Disabled Message Displayed After Extended Idle, Multiple PCM DTCs P0171, P0174, P0420, P1516, P1682, P2101, P2176 (Reprogram PCM) - (Apr 12, 2006)

LD8, L37 Service Engine Soon (SES) Light Illuminated or Traction Disabled Message Displayed After Extended Idle, Multiple Powertrain Control Module (PCM) Diagnostic Trouble Codes (DTCs) -- P0171, P0174, P0420, P1516, P1682, P2101, P2176 (Reprogram PCM)


Models: 2006 Buick Lucerne -- Built Prior to VIN Breakpoint 6U211174

2006 Cadillac DTS -- Built Prior to VIN Breakpoint 6U211176

with 4.6L Northstar® V8 Engine (VINs Y, 9 -- RPOs LD8, L37)

Condition
Some customers with vehicles built prior to the above VIN breakpoints may comment on any of the following conditions:

• An SES light illuminated or a "Traction Disabled" message displayed after a extended idle of 30 minutes or more. After further investigation, technicians may find DTC P0171 and/or P0174.

• An SES light illuminated . After further investigation, technicians may find DTC P0420.

• An SES light illuminated . After further investigation, technicians may find DTC P1682 along with P1516, P2101 or P2176.

Correction
Reprogram the PCM with the latest TIS calibrations if the above concern is encountered. An updated PCM calibration is now available to address this concern. This calibration, or any that follow, is designed to address this concern. Refer to Service Programming Systems (SPS) using the appropriate Service Information (SI) procedures. This latest calibration also contains diagnostic enhancements for the "Traction Disabled" message displayed after an extended idle.

• If P0171 or P0174 is present, check for vacuum leaks. If vacuum leaks are present, P0171 or P0174 will continue to set.

• If P0420 is present, refer to DTC P0420 diagnostic "Repair Verification" in SI after reprogramming to determine if the catalyst is "Good" or "Bad". Do not replace the catalytic converter unless DTC P0420 does not pass with the new calibration.

The new PCM calibration is available to dealerships as part of TIS2000 incremental satellite update data version 4.0 for 2006 or later, broadcast to dealers on April 3, 2006; and on TIS CD-ROM version 4.0/2006 or later, mailed to dealers beginning April 12, 2006. As always, make sure your Tech 2® is updated with the latest software version.

Share this post


Link to post
Share on other sites

Thanks for the info, Logan. But, as it turns out, it's definitely a vacuum leak.

On a hunch today, I decided to inspect the (new) EGR valve... the one Sewell Cadillac (<=horrible) charged me $500 to put a new gasket under. As it turns out, when they removed it, one of the bolt holes was stripped. They must have noticed this and put a slightly larger spare bolt in the hole. It may have grabbed a few of the remaining threads and then stripped them out. It was barely finger tight. Wouldn't one think they would have properly rethreaded the hole? If they had, I'd have been happy and they could have kept the $500 they had to refund to me.

Anyway, I put a little larger bolt in just to test it. It ran like new!!! No rough idle, no jiggling engine!! I don't plan to drive it this way. I am going to buy the tools I need to rethread the hole and a fitting bolt that can be properly tightened.

After I have it all fixed and can drive it some, I will report back as to the success of the repair.

Share this post


Link to post
Share on other sites

Quick question... would it work best to use a tap and die or tap it and use a heli-coil? The crossover is kind of soft aluminum and I wanna make sure its gonna hold permanently!

Share this post


Link to post
Share on other sites

I would think a Heilicoil would be the strongest repair vs. just tapping the aluminum but the threads from the factory were not inserted. A Heilicoil would work in this case since those bolts are not tightened like a head bolt.

Does the hole in the aluminum go through or is it a blind hole? If it is through, I'd use grease on the drill in order to keep the chip ingestion to a minumum.


Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

Share this post


Link to post
Share on other sites

I don't believe it goes all the way through. Only place the metal chips would really go is in the EGR holes. I'll tape over them to be safe and I'll vacuum up afterwards. I'll stop by a parts store today and see what I can find for tools to tap and die. Looking forward to having this all fixed after months!

Share this post


Link to post
Share on other sites

A TimeSert is available for just about every aluminum thread in Cadillac and most other makes. The thread insert number is part of the Engine-Mechanical section in older FSMs and probably in the 2006 model year FSM too.


CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Share this post


Link to post
Share on other sites

Did not expect the software to fix the miss....just the false 171-174 and service traction control together issue.

Time-Serts are the prefered method to fix bad threads. That said...they are likely cost prohibitive.

The Time-Sert tools are part of expensive dealership kits. So obtaining a kit for head bolts repairs can be justified....a stripped EGR bolt no.

The kit needed for the Northstar non- headbolt repairs is J-42385-2000. It's about $500 used on eBay.

For the headbolts...its a different kit....and there are different headbolt kits for different eras of Northstars.

It should be noted there are over a dozen different J-42385 kits. Each with a differnet suffix...-100, -200, -300, -500, -2000, -2030 etc.

Some of the kits can be rented.

http://www.ledfix.com/j42385toolrental.html

Share this post


Link to post
Share on other sites

My opinion is a Timesert would be overkill in that situation and a Heilicoil probably would be too. The stud is only torqued to either 89 or 132 inch-pounds - a tiny fraction of what a head bolt is torqued. Those threads were just in the aluminum from the factory anyway.

If the hole is blind (does not go through), you will want to buy a "bottoming tap" as a regular tap will not get full threads near the bottom of the hole and you risk stripping out the new threads.


Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

Share this post


Link to post
Share on other sites

Some years ago I had a battery post pulled out of the battery case, leaving a crack in the battery case which was an acid leak. It sure looked to me like the guy was green and used an air wrench to tighten a side-terminal battery. The dealer gave me a new battery when they found out.

Your situation is obviously different, particularly if you have a blind hole that needs to hold 132 inch-pounds (11 lb-ft) or less. From what Logan says, an insert is impractical when a drill-tap will fill the bill perfectly.


CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

Share this post


Link to post
Share on other sites

All I have been able to figure is that if I drill and tap the hole, I'd have to go up from M8 to M10. That may be too big. So, I found a slightly larger SAE bolt and put it in for now. It has held for about 300 miles and the car is running better than it has in probably 9 months. It has not dinged and no traction control or stabilitrak messages.

I ordered an M8-1.25 heli-coil set to fix the holes.

I am also replacing the catalytic converter, O2 sensors, and spark plugs. After all that, it should last me a while.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.