: idle vibration and no other codes/symptoms



mhamilton
03-30-11, 07:43 PM
Looking for some ideas or suggestions... I don't know what else I can check with this problem. Gradually since I got the car I've noticed the idle getting slightly worse. It's not a rough idle like a misfire, just a very slight vibration I feel in the steering wheel. And on a cold start, it will actually vibrate very noticeably--worse when it's colder outside. Some times when cold I can even feel it in the floor and door when it's first started. Once the engine is up to temp it settles down and it's just the slight hum in the wheel.

Anyway... around 75k miles I really started noticing the cold start vibration. So that's when I did the top end cleaning and replaced the plugs hoping to fix that. The plugs were fine, but found some corrosion on 2 of the front coil pack contacts. Cleaned all of that. It didn't really change anything.

No codes, and no driveability problems. Mileage is great on the highway. Dog bone bushings are still tight. Was thinking the motor mounts could be going, but don't they last on engines with the dog bones? I've noticed when first started if I rev the engine to 1000 or 1500 the vibration gets worse! It's actually better once I put it in gear and it idles down. With the hood open, I can even see the engine vibrating.

I can't think of what else to check... Thought about plenum boot and vacuum leaks, but those should set a "lean" code. No coolant is ever lost. I can't think what else would cause this vibration. It's especially annoying after driving my friend's '08 Cobalt, which with 80k miles idles like the engine is shut off :bonkers:

Ranger
03-30-11, 11:08 PM
Dog bone bushings are still tight. Was thinking the motor mounts could be going, but don't they last on engines with the dog bones?
Yeah, the dog bones really save the mounts.

How's the MPG? Have you checked the injectors and FPR?


The plugs were fine, but found some corrosion on 2 of the front coil pack contacts. Cleaned all of that. It didn't really change anything.
Good contact on the boot spring?

mhamilton
03-31-11, 07:13 AM
Yeah, the dog bones really save the mounts.
How's the MPG? Have you checked the injectors and FPR?

Ok that's good, I didn't think the mounts were bad. I'm pretty sure looking at the engine vibrating that they're doing their job isolating me from the worst vibrations.

MPG is great... got 29 mpg hwy with a packed trunk and back seat last week. How would you suggest checking injectors?

Oh--just thought of this: could an aging/weak battery cause this kind of odd problem? I have no starting or running problems, no electrical gremlins, and static charge still indicates over 50% charge. But the battery is on the list of things to go, it's 5 years into a 7 year warranty (ACDelco). I have noticed that when I brake I see the headlights dim slightly (I chased that issue for a bit, but chalked it up to an older battery and/or alternator).


Good contact on the boot spring?

Seemed good and tight, I cleaned them all as well.

Submariner409
03-31-11, 08:06 AM
I know this is going to sound lke a broken record - but have you tried running a 20 oz. jug of TECHRON in a tank of Shell, Texaco, or CHEVRON 91/93 octane ? ANY cold idle improvement might point to something in the fuel system.

Braking - headlights dim a bit...........what's the DIC voltage during this sequence ? Any voltage drop ? Clean, tight battery terminals and ground connection to the body ?

Ranger
03-31-11, 11:34 AM
Listen to each injector with a stethoscope. You should hear a rhythmic ticking as it pulses.

mhamilton
03-31-11, 07:18 PM
I know this is going to sound lke a broken record - but have you tried running a 20 oz. jug of TECHRON in a tank of Shell, Texaco, or CHEVRON 91/93 octane ? ANY cold idle improvement might point to something in the fuel system.


I was thinking of doing just that. I do usually run Shell high octane whenever I can, though. I will put some in when I make my next long highway trip.

I thought about changing the fuel filter, but the pipe is all rusted at the filter nut. I'd have to get a complete line off another Eldo. And I don't think that would affect the idle alone, not without causing fuel starvation all the time.


Braking - headlights dim a bit...........what's the DIC voltage during this sequence ? Any voltage drop ? Clean, tight battery terminals and ground connection to the body ?

Oh I went through the whole thing with that when I first noticed the lights. The DIC doesn't fluctuate even a tenth of a volt when I hit the brakes, just the slight dim of the headlights. I checked and cleaned the battery terminals, checked grounds (measured resistance) at the headlights themselves, etc etc, and it all tested fine. The only thing that I ever noticed, once or twice (since Sept '09) time when I was coming to a stop from ~50mph, the battery light came on for about 2 seconds, then went out. Not even enough time to scroll through the DIC to see the voltage. And no codes are ever stored.


Listen to each injector with a stethoscope. You should hear a rhythmic ticking as it pulses.

Okay, I'll try that. I've done that before to check for stuck injectors, but there's definitely no driveabilty issues other than the slight idle vibe.

drewsdeville
04-01-11, 12:42 AM
I'm pretty sure looking at the engine vibrating that they're doing their job isolating me from the worst vibrations.


I don't know, this sort of throws up a red flag for me. You can SEE the mounts "doing their job"?

If you really want to take the mounts out of the equation, jack up the car and do some probing with a large prybar, looking for excessive movement, signs of leakage, etc.

If you suspect a misfire, you can always hear it at the exhaust tip(s). You can hear the distinct "put-put" of a misfiring cylinder much easier than you can feel it.

mhamilton
04-01-11, 12:39 PM
I don't know, this sort of throws up a red flag for me. You can SEE the mounts "doing their job"?

If you really want to take the mounts out of the equation, jack up the car and do some probing with a large prybar, looking for excessive movement, signs of leakage, etc.

If you suspect a misfire, you can always hear it at the exhaust tip(s). You can hear the distinct "put-put" of a misfiring cylinder much easier than you can feel it.

Well of course, I can't *see* the mounts doing anything. What I meant was, I don't really suspect the mounts as the problem. For one thing, with the strut bushings tight the engine can't move anywhere. What I was trying to get at was that I can see the engine/cover vibrating (not shaking) and feel it strongly when touching the the engine. The vibe is not nearly as strong in the car, as it shouldn't be with motor mounts and subframe isolators.

I will check on the mounts just for peace of mind.

It's not really harsh enough to be a misfire (thought I guess it could be a slight one). Honestly it feels more like a small rotating imbalance, but I have no idea how that would be dependent on temperature, and some times be better than others.

mhamilton
04-01-11, 06:28 PM
Now today it was 60F on the way home, and at stop lights (some lengthy with Friday traffic) my idle vibration was almost nil (once the engine warmed up). I have no idea what would be causing it to be so bad in cold ambient temperatures, and then almost disappear when it warms up.

Ranger
04-01-11, 09:26 PM
That's a stumper.

mhamilton
04-01-11, 10:01 PM
I don't know why these obscure problems seem to find me! lol

I can't think what it could be, except maybe some odd problem with the battery or maybe one of the coils. But that's a stretch, because the coils would be hotter than anything once the engine heated up. And thought about a cracked plenum or intake gasket, but the PCM would compensate for that based on O2 sensor readings until it got bad enough to trip a CEL for lean conditions.

Unless the problem is much deeper internal to the engine. I do still get the cold start knock, and sometimes even when the engine has sat for a few hours, enough for the engine to come down to ~100 degrees, it will knock at startup for a minute. I'm wondering now... I know it's not common, but ever heard of issues on these engines with timing chain tensioners wearing out?

Ranger
04-01-11, 10:12 PM
Have you checked the plenum to rule it out? I have noticed it cause some strange reactions that I would never have thought of.

A bad ICM crossed my mind as well. If you're gonna go after that, then get one from a junk yard and swap 'em with that. Hate to see you spend a lot of money on a new one as a shot in the dark and have it fail the test.

00 Deville
04-01-11, 10:21 PM
thought about a cracked plenum or intake gasket, but the PCM would compensate for that based on O2 sensor readings until it got bad enough to trip a CEL for lean conditions.

It's worth a try to suspect the plenum... the idle on my 2000 smoothed out after changing the plenum (small crack at the 6'oclock position) and it never set a lean code. I sprayed brake kleen all along the perimeter of the plenum... I used a 18" extension nozzle to get the bottom good... where the usually crack. When it started sucking in the brake-kleen I got thick white smoke out the tailpipes.

mhamilton
04-02-11, 08:16 AM
Ah... now that gives me something to look for! And I can imagine a small crack would close up a bit as the engine heat expanded the plastic, giving me the better idle when hot. I had assumed that any crack would set a lean code. I'm definitely going to check that asap, because mine's at the age where old plastic starts to break. And this car has seen so many heat cycles with the previous owner... it would not surprise me in the least!

Bad ICM is something to consider as well. Every once in a blue moon I'll be idling and catch the rpm drop a hair and then go back to normal. But I never put that past more than a blip with the IAC or engine load.


It's worth a try to suspect the plenum... the idle on my 2000 smoothed out after changing the plenum (small crack at the 6'oclock position) and it never set a lean code. I sprayed brake kleen all along the perimeter of the plenum... I used a 18" extension nozzle to get the bottom good... where the usually crack. When it started sucking in the brake-kleen I got thick white smoke out the tailpipes.

When you did the plenum, are there any other hidden vacuum elbows under the manifold I should replace at the same tiem? Now that I know the plenum can crack w/o setting a code, I'm leaning toward that as the problem. After I check it with spray, I'll get the plenum, TB gasket, prob intake gaskets as well. Anything else while I'm under there?

00 Deville
04-02-11, 11:26 AM
When you did the plenum, are there any other hidden vacuum elbows under the manifold I should replace at the same item? Now that I know the plenum can crack w/o setting a code, I'm leaning toward that as the problem. After I check it with spray, I'll get the plenum, TB gasket, prob intake gaskets as well. Anything else while I'm under there?

When I changed my plenum I also replaced the 8 intake gaskets which may not of been necessary but they are cheap... 8 Fel-Pro intake gaskets run about $14. I also inspected all the vacuum lines and found a hose and a grommet that had become hard with age and didn't fit as tight as I'd like them too. They were the small 2" long hose that connects to the front valve cover and the rubber grommet that the PCV rattle valve fits in on the rear valve cover. I went ahead and replaced the PCV valve while it was out. I got the Plenum, PCV valve and grommet from Chris at Rippy.

With the intake out it's also a great time to go ahead and give the throttle body and IAC valve a good cleaning. I think it probably took about 2 hours to do the whole job... but I wasn't in a hurry either.

mhamilton
04-02-11, 02:14 PM
Thanks! Sounds good to me. I just got some more brake clean, so I will check that soon. And it will be nice to give the TB a thorough cleaning. I've done it from the outside twice, but I know there's plenty of dirt I couldn't reach.

I read through the plenum DIY thread this morning, looks like some people pull the injectors, others don't. It seems easier to me to remove the 2 quick disconnects from the rail and leave the injectors in the intake. Any issues with doing that?

I hate the fact that I'm in an apartment now... if I had access to my garage I would be out there right now pulling it apart! LOL

Ranger
04-02-11, 03:44 PM
I don't think there is any need or advantage to pulling the injectors.

mhamilton
04-02-11, 04:26 PM
Thanks! I didn't see why it would be necessary unless there was some kind of clearance issue. Would be much easier to just leave them. Well I will be checking on that soon, and hopefully I can replace that next weekend. I'll post back if it fixes my issue!

00 Deville
04-02-11, 04:41 PM
it will be nice to give the TB a thorough cleaning. I've done it from the outside twice, but I know there's plenty of dirt I couldn't reach.

I read through the plenum DIY thread this morning, looks like some people pull the injectors, others don't. It seems easier to me to remove the 2 quick disconnects from the rail and leave the injectors in the intake. Any issues with doing that?

With the intake out it really makes cleaning the TB easy since you can get to both sides of the butterfly. I did disconnect the 2 quick disconnect fuel lines and pull the injectors.... not sure why I did :hmm:... but I did. If you do end up pulling the injectors... putting a drop of motor oil on the o-ring of each injector, makes them go back in real easy.

mhamilton
04-02-11, 05:58 PM
Just looking at parts online, is there any reason not to buy the $2.50 Felpro (blue) TB gasket instead of the $17 Delco (black) TB gasket?

Oh yes, I've done injectors before, I was more worried about with whether I should get new orings or not. If I pull them out I hate to reuse an oring. I know, it's only a few dollars, but if it's something I don't need to get... I'd just as well leave them alone.

00 Deville
04-02-11, 07:29 PM
Just looking at parts online, is there any reason not to buy the $2.50 Felpro (blue) TB gasket instead of the $17 Delco (black) TB gasket?

Oh yes, I've done injectors before, I was more worried about with whether I should get new orings or not. If I pull them out I hate to reuse an oring. I know, it's only a few dollars, but if it's something I don't need to get... I'd just as well leave them alone.

I reused both the TB gasket and injector gaskets... even though they were 11 years old they appeared to be in very good condition. If you were going to replace them I would go with the Fel-Pro... due to the substantial price difference.

mhamilton
04-04-11, 01:22 PM
Ugh.... I can't even test the brake clean spray because I have no tools to remove the vanity cover. The heck with it, I called my local dealer and he has plenums in stock. If this dealer stocks them, you can bet it's a common item! And my NAPA has the FelPro intake and TB gaskets, so Saturday morning I will take care of all that. Hopefully that will fix this annoying issue!

00 Deville
04-04-11, 02:25 PM
The heck with it, I called my local dealer and he has plenums in stock. If this dealer stocks them, you can bet it's a common item!

I'd be surprised if there was a Caddy dealer that didn't stock the plenum's. Good luck with changing it out and hope you're able to find all the tools you need after your recent move.

mhamilton
04-04-11, 05:44 PM
I don't think they're actually a Caddy dealer, just recently became "Hendrick Auto Mall" (formerly Hendrick Chevy). But whatever, as long as they have it lol

Thanks :) I'm heading back home to work on it this weekend, so I should be able to get it done. Also, my coworker and I were talking about it, he's going to bring his good OBD scanner so we can look at misfire counts and O2 data just to confirm it's not some flakey ignition coil.

mhamilton
04-09-11, 08:31 PM
So I got my new plenum and intake gaskets on today. The old plenum was actually not cracked at all. Though the rubber was certainly on its way out, quite hard and I'm sure with enough flexing would crack. What looked worse was actually the sealing surface to the crossover face. Cleaned that up with some fine grade sandpaper. Replaced the intake and TB gaskets, torqued to spec. Actually no difference in my idle vibration on a cold start. Hmmm... that is disappointing. Still need to look at sensor data with a live view scan tool.

Found a couple things--on the PCV fresh air pipe, the 90* elbow at the TB was cracked. I think this could certainly cause problems, leaking air after the MAF, but I taped and clamped it with no change. I will replace that line later this week.

Also when I looked into the end of the intake with the PCV vacuum pipe, there was lots of oil reside all over the inside. I would have liked to replace that PCV line as well, but not sure I can do that at this point with the power steering pump in the way. Felt like it was on there tight, anyway.

LOTS of oil inside that intake and around the intake ports. This is with a new PCV valve as well.

Oh, and yes the fuel rail does need to be removed in order to access the intake bolts. Thought I could do it without, but there's one right under the FPR. Was not a big deal, and I did reuse the orings after cleaning and oiling them. Didn't feel bad about that with the plastic intake, they pulled out with little resistance, so I'm sure they are fine.

Ranger
04-09-11, 10:46 PM
LOTS of oil inside that intake and around the intake ports. This is with a new PCV valve as well.
Normal and harmless.

mhamilton
04-10-11, 01:52 PM
Took the car out this morning for the 1st time since the repair. I have to say, the smoothness going down the road is noticeably better! It was always smooth before, but now it's like riding on glass. And it did seem to improve at stoplights, it's nearly gone I'd say.

But... it's as bad as ever on a cold start. I did notice this new symptom. When I first started it this morning, it was actually smooth. Then after about 10 seconds or so at 1000 rpm it starting shaking. The only thing I can think of is that this is when the PCM changes from "starting" mixture to "cold idle" mixture... or maybe changes the timing? Maybe not... I'm still baffled. I'm going to get the new PCV air tube and see what that does before I go nuts chasing some mystery leak--and look at the live sensor data. All the other vacuum lines are in good shape (I had previously replaced some rubber hose feeding the hvac controller)

mhamilton
04-19-11, 12:24 PM
Ok this is getting silly. It was foolish of me to throw all those intake parts at the car without a proper diagnosis, but okay that's done and the plenum is good for another 10 years. I got the new PCV breather pipe, the old one was falling apart at the TB connection. It is now quite a bit smoother at idle when I've just gotten off the highway.

But on cold starts, still bad. Passengers can even feel it in the floor. And this is strange--I drive the car to lunch, it gets up to temp and idling smoothly. Got to lunch, come back 40 minutes later and start it up. The temp gauge is just a tick under 12:00, and it's idling rough again. That just baffles me. How could it idle good hot, but not after I stop/restart it?

Unfortunately the scan tool I borrowed does not show misfire counts like the GM tool. Not sure if any aftermarket scanner does that or not. But I'm also not going to throw ignition parts at it without knowing if it's missing.

I'm just at a loss... was just thinking, when I did the plugs I reused the old plug boots. Maybe one or more is bad? I didn't see any carbon tracks or anything wrong with them. They were pliable and just needed the dust wiped off.

Submariner409
04-19-11, 01:59 PM
I just skimmed back through this thread..........did you clean the EGR valve ?? One little carbon chip in that pintle bore will cause all sorts of weird idle problems.

mhamilton
04-19-11, 04:15 PM
Now there is a good idea! I assume too much with OBDII to tell me when the EGR starts acting up, but I'm sure there could be a little leakage that will not cause the position sensor to set an error code.

In fact, now that you mention it, the GM procedure for after doing the Top End Cleaning says that the EGR should be checked and cleaned. And it makes sense that the EGR being open when cold would make the idle that much worse than when hot.

Well damn, I'm going to check that first thing Friday! I will have to see if I can get an EGR gasket from NAPA or somewhere before the holiday weekend.

Ranger
04-19-11, 09:04 PM
Many times you can get away without replacing the EGR gasket if you can get it off without destroying it. I have.

mhamilton
04-19-11, 09:47 PM
That's good to know. Although my NAPA should have a new EGR gasket for me Friday morning, so it should be good either way :)

I would have never thought of the EGR because there are no other driveablity issues--perfectly smooth on acceleration and starts up instantly. I've had EGR valves fail before, but on those when I pressed the gas the engine stumbled or the engine would stall as soon as it started (well, this was in the carbureted era). But the kind of vibration I have is reminiscent of an open EGR; definitely fits the characteristics. I just hope it fixes it! Today I was in traffic and the vibration felt worse than ever...

mhamilton
04-27-11, 12:50 PM
So I did the EGR cleaning this past weekend. It really didn't look clogged up from what I could see. I did carefully spray it out and used a pick to clean any buildup from around the pintle. I honestly did not think it would make a bit of difference, I've seen EGRs far worse than this one. But today on the way to work, I was surprised to stop at a light while the engine was only around 10 o'clock temperature and the idle was nearly perfectly smooth. Go figure! Maybe coincidence, but it sure didn't hurt to clean it :)

I did still have a bit of almost what felt like a mis when I was leaving work the other day, but that was a very long stop light and the engine was at C. Still no codes.

Another thing I noticed, when I was cleaning out the EGR, the rubber seal around the pintle shaft looked pretty torn up around the shaft itself. Is that the only seal for that EGR? Or is that more or less a dust cover? I'm not sure what it should look like inside.

Ranger
04-27-11, 02:26 PM
I think that is just to keep the exhaust gases from carboning up the internals of the motor.

MoistCabbage
04-28-11, 03:49 AM
Just a thought, have you considered bad motor mounts? Last winter I noticed a vibration in the steering wheel, which quickly progressed to a vibration through the floor. I could hear it as well, almost a slight grinding noise. I figured my front mount was bad, it turned out all but the rear mount were completely trashed. It seemed worst between 1000-1700 RPM, noticed it most on cold starts.

mhamilton
04-28-11, 07:35 AM
I'm starting to wonder... we had talked about that back on page 1 of this thread, but I didn't pursue it too far. Your description sounds almost identical to mine as far as the rpms. But my engine has the torque struts, so I didn't think the mounts really went bad. Then again, after seeing how the rubber boots on my tie rods deteriorated after 10 years, it's not that unbelievable.

I had looked at my rear mount last weekend, seemed fine from what I could see. But I have to get it back on jackstands to check some more steering stuff, I will look when I do that.

So to check these mounts, should I disconnect the torque struts and do the brake-torque test?

Ranger
04-28-11, 09:55 AM
Maybe just drop the lower splash shield and have a look at it.

MoistCabbage
04-28-11, 01:13 PM
Make sure you check them all, not just the front. In my case, the rear was in ok shape, but the front, left, and right were disintegrating. After the new mounts were installed, the car was perfectly quiet and smooth again, but I thought the slight grind/grumble noise (when the old ones were in) was suspicious. I went over everything with a stethoscope just in case, nothing, smooth as silk. It was very deceiving. I probably wouldn't have suspected the mounts either if it didn't clunk on acceleration. If you do have bad mounts, your torque struts might be keeping that at bay.

mhamilton
04-28-11, 06:33 PM
I will have to look at it then. I do know the trans mount looks good, I was under there just recently. No noises from my drivetrain, no clunking. When I did the water pump gasket I noticed the torque strut bushing was looking dried out, but it was not loose or falling apart. I also noticed one of my subframe bushings was looking dried out, but not all of them.

I don't recall being able to see much on the front mount last time i was under there, even with the splash shield out. I probably looked at it when I did my ac last summer. What should I be looking for? Any dryness/cracking at all? These are hydraulic mounts, correct? So it's possible they could collapse if the uncured rubber leaks out?

I will definitely take a look, but I'm not sure. Hmmm... I still don't think the engine should vibrate at all, regardless of the mounts. Replacing the mount may mask it, but I'm not doing that job unless it's obviously failed. I don't know, maybe I'm being too picky about this idle vibration. I can also feel the radiator fan when those are running, maybe I'm just expecting too much.

Ranger
04-28-11, 08:53 PM
You are correct in that the front mount is difficult to see even with the splash shield removed, but you can get a peek at it and a finger on it. It IS hydraulic so if it is bad, you should see it wet with oil.

00 Deville
04-28-11, 10:26 PM
My 2000 has never idled quite as smooth as my 2002. The reason why is explained in the bulletin below. If your idle has always been a little rough this bulletin may apply. If it's not as smooth as it used to be it probably doesn't apply. I would still take a hard look at the front motor mount... they are a known issue. I am replacing mine while the motor is out due to a small tear... but I don't have the torque struts like your Eldo has either.

4.6L LD8 , L37 and 4.0L , L47 Engine Rough Idle - kw body calibration camshaft code DTC EGR intake leak lean manifold MIL miss misfire PCM #PI01748A - (02/20/2004)

4.6L LD8, L37 and 4.0L, L47 Engine Rough Idle.
[/URL][URL="http://127.0.0.1:9001/servlets/BlobShtml?ShtmlFile=1462322#ss1-1462322"]Condition/Concern: (http://127.0.0.1:9001/servlets/BlobShtml?ShtmlFile=1462322#ss1-1462322)

Some 2000 and early built 2001 model year Cadillac Deville, Eldorado, Seville with 4.6L (LD8, L37) engines or 2001 Oldsmobile Aurora with 4.0L (L47) engine, may exhibit a condition of rough idle with no PCM DTC and no driveability complaints
(http://127.0.0.1:9001/servlets/BlobShtml?ShtmlFile=1462322#ss2-1462322)Recommendation/Instructions: (http://127.0.0.1:9001/servlets/BlobShtml?ShtmlFile=1462322#ss2-1462322)

The camshafts must be replaced (part numbers are listed below) on all 2000 vehicles with 4.6L (LD8) (L37) Engines and the early built 2001 vehicles (see broadcast codes listed below) with 4.0L (L47) OR 4.6L (LD8) (L37) Engines. For a 2001 vehicle, you must verify that it has the early cam profile by reading the 3 alpha characters of the broadcast code listed on the tag attached to the passengers side of the engine's rear cam cover. The Broadcast Codes for early 2001 engines are:
Seville, Deville Applications:
ENGINE VIN CODE Y KMA
ENGINE VIN CODE 9 KKA
.
Eldorado Applications:
ENGINE VIN CODE Y KCA
ENGINE VIN CODE 9 KBA
.
Aurora Application:
ENGINE VIN CODE C KYA
.
Camshaft Service Part Numbers:
.
4.6L (LD8) VIN CODE Y AND 4.0L (L47) VIN CODE C CAMSHAFT SERVICE PART NUMBERS;
12570331 RH EXH
12570332 LH INT
12570333 RH INT
12570334 LH EXH
.
4.6 (L37) VIN CODE 9 CAMSHAFT SERVICE PART NUMBERS;
12570335 RH INT
12570336 LH INT
12570337 RH EXH
12570338 LH EXH
NOTE: the Camshaft Service Part Number information can also be found on page 7 of the July 2001 GM Tech Link Volume, No. 7
SPECIAL NOTE: If you are having difficulty setting the mechanical timing on the rear bank exhaust camshaft. SI and the Service Manual instructs you to set the exhaust camshaft gear so that the stamping "RE" is in the 12 o' clock position. It has been found the "RE" stamping is located in the incorrect position on the exhaust camshaft gear. The correct positioning of the Exhaust Camshaft is when the camshaft dowel pin is in the 12 o' clock position. and the Exhaust Camshaft gear "RE" stamping is in the 9 o' clock position .
Once all 4 camshafts have been installed, the calibration must be updated. The dealer must contact TECHLINE and tell them that the camshafts on the vehicle have been replaced, and they will give the Dealer a VCI number to install the correct calibration. Techline must be contacted each time so that they have a record of when a camshaft change occurred on each vehicle. This will ensure that future calibration for that vehicle will be correct.
.
Please follow this diagnosis process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed. If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance. This diagnostic approach was developed for the vehicle with the VIN you entered and should not be automatically be used for other vehicles with similar symptoms.
(http://127.0.0.1:9001/servlets/BlobShtml?ShtmlFile=1462322#ss3-1462322)
(http://127.0.0.1:9001/servlets/BlobShtml?ShtmlFile=1462322#ss3-1462322)

mhamilton
04-29-11, 07:11 AM
Oh that's right, I remember the 2000's cam problem. But hopefully it is not that! It will idle nearly perfectly smooth after it gets good and hot. It's mostly the startup and cold idle roughness that has been bugging me, the warm idle has smoothed quite out a bit since I started down this rabbit hole.

Maybe it is all due to a bad mount, you've got me thinking about that now. I will have to take a look and see what I can find.

00 Deville
04-29-11, 07:40 AM
Oh that's right, I remember the 2000's cam problem. But hopefully it is not that! It will idle nearly perfectly smooth after it gets good and hot. It's mostly the startup and cold idle roughness that has been bugging me, the warm idle has smoothed quite out a bit since I started down this rabbit hole.

Maybe it is all due to a bad mount, you've got me thinking about that now. I will have to take a look and see what I can find.

From your description I don't believe all the vibration your experiencing is from the cam issue. Just wanted to make sure that you were aware of it in-case you where to compare your early N* to a latter one.