: Help!! Low RPM accel rattling



Sloand
11-16-11, 04:30 AM
I am a first time Cadillac owner this year and I received a 2005 Cadillac STS V8 as a gift. Every since I took ownership of the car it makes a diesel like rattling sound whenever I accelerate in low RPM range 1500-1800. I have done exhaustive research before bringing into the dealership. I have tried higher octance gas...no luck. Made sure the oil level was good and even changed...no luck. Finally brought it into two dealerships, the first told me some torquing of the intake bolts, computer program and the front cam actuators that were leaking would fix the problem. Wanting a second opinion I brought it to another Cadillac dealership and they actually drove the car and kept it for a few days trying to simulate the sound but of course they could not "Murphys law" They ran for codes and nothing out of the ordinary came up. I did have them replace the leaking cam actuators, a valve gasket that was starting to leak and do the computer update. Of course the problem is still not solved. I was hoping that maybe someone who had a similar experience could help with any information. Thanks all!

scott9001
11-16-11, 08:46 AM
no help here your sure its not an exhaust shield or something of the guts of the cat are not rattaling around

Sloand
11-16-11, 10:25 PM
no help here your sure its not an exhaust shield or something of the guts of the cat are not rattaling around

Absolutely positive that it has nothing to do with the cat/exhaust anything. This is a low RPM accel issue that is making a very distinct dieseling sound that would only originate from the engine. Thanks for the quick response though. Much appreciated!

MacMuse
11-17-11, 12:33 AM
Mine happens at 1200-1400 RPM. I'm still collecting info to present a strong statement to Service when I bring it in for this.

I recently had some work done around the intake manifold, and I really thought the issue was gone for a week - bit now I'm feeling it practically every time I drive.

Torque converter & loose intake manifold bolts are the most frequent potential causes but I'm not confident I can convince Service to take it seriously. At least they didn't when I reported it a year or so ago.

thembones
11-21-11, 12:04 AM
The clunking sound on my STS ended when the rear differential bushing was replaced.

STS guy
11-21-11, 09:57 AM
I have experienced the same "diesel" sound at low rpms. It seems to me it happens after the first start-up in the morning before the engine is fully warmed up. Seems to go away after the engine has warmed up. I have no idea what is causing it. Immediately thought it was low on oil but, it is not. Oh well, I have a bump 2 bump warranty. If something blows I'll let Cadillac pay for it.

Spyke
11-23-11, 06:04 PM
is this a noise like this:

http://www.cadillacforums.com/forums/cadillac-cts-first-generation-forum-2003/243821-noise-video.html

Mine is doing the same thing (2005 CTS) but only at 1700 rpms to 2200 rpms on low acceleration.

jkharnage
12-10-11, 12:46 AM
I had a similar concern three years ago. First, the dealership did replaced the torque convertor per a GM bulletin. The noise went away for awhile but I also could hear the same sound billowing back and it seemed to come from the rear end. I reside up north (Cold --- tundra) and a lot of salt is thrown on the roads. I spray the underbody for the vehicle quite often. I grabbed my compressor and electric tape w/ .5 or .75 inch heater hose and pressurized the rear differential. BE CAREFUL! Just increase the pressure by 5 to 10 psi (regulated). Basically, the vent above the differential was plugging up. I could hear the air being relieved through the vent. Problem solved. I usually do this every year ranging from the mid winter or early spring to eliminate the noise. I can usually tell when it’s time to get the compressor out due to the low pitch growl. Hope this will work for you.

scott9001
12-10-11, 10:38 PM
you know what verry wierd last time i changed the oil on my 05 i checked the rear diff fluid right before i put it away for winter and there was pressure on the system and i was thinking i am going to have to find the vent and free it up do u really think this is a good idea to try?

CapnCurt
12-11-11, 12:53 PM
I hear a slight noise from mine at low exceleration but it seems to be come up from behind dash on the driver side like some springs vibrating or something, I'm not sure what it is. does that sound like about the same area you hear your noise coming from?

Ludacrisvp
08-03-13, 12:26 PM
I had this issue recently, this solution did fix it.
The article claims only valid for 2 model years but I would bet that this was an issue longer than this.

Exhaust - Rattle Noise From Center Of Vehicle At Idle

TECHNICAL
Bulletin No.: 09-06-05-003
Date: April 29, 2009
Subject: Exhaust Rattle Noise from Center of Vehicle at Idle and Partial Throttle (Repair Exhaust Heat Shield with Clamp)
Models: 2008-2009 Cadillac SRX, STS

Condition:
Some customers may comment on a metallic sounding rattle heard from the mid-section of the vehicle. The rattle can occur during both hot or cold exhaust system conditions and at engine idle and/or partial throttle.

Cause:
This condition may be caused by a cracked exhaust heat shield on the right front inlet pipe of the muffler assembly.
The heat shield is typically cracked at the rear weld to the pipe, which allows a rattle between the shield and the pipe.

Correction:
Important DO NOT replace the exhaust system or muffler for this concern.

http://i.imgur.com/81aSONN.jpg

1. Locate the exhaust heat shield on the right front inlet pipe (1). Verify that the heat shield rear weld to the pipe is cracked and loose from the pipe.

http://i.imgur.com/Yg4c1fr.jpg

Important Use the clamp specified in the Parts Information below. DO NOT substitute with another clamp.

2. Attach the clamp to reattach the loose end of the shield to the pipe (1). Be sure to locate and orient the clamp over the shield to ensure the clamp captures the rear part of the shield.

http://i.imgur.com/dta6EDE.jpg

3. Orient the clamp so that the bolt is on the outboard side of the pipe (1). The bolt and clamp shoulder should be located as shown.

Tighten the clamp bolt to 2.5 Nm (22 lb in).

http://i.imgur.com/mLtE4t5.gif

Guy.Seminerio
08-04-13, 03:29 AM
Does it make the noise if you get the car to those rpms while in park or neutral? If so have someone put the car at those rpms and you get under the car and try to pinpoint where it's coming from. Push up on the exhaust. May be a broken bracket. Follow the sound. Push up on stuff tightly to see if that stops the rattling. Get the car on jack stands if need be. Heat shield has happened to me on previous cars.

By that sound in the video something is loose. Doesn't sound like you're running lean which is why I assume you tried higher octane gas. Good luck.

neverlateSTS
08-09-13, 12:09 AM
i had the same diesel sound in my 07 nstar and after a torque converter change all new mounts and replacing the crank hub that drives the clutch fan the bushings do wear out i was sure it was found. no luck. GM even sent some magical engineering student and it was determined that sound is exhaust pulses rattling within the right front pipe. I asked them to replace and was told this is normal for this engine and there is nothing to be fixed. Try taking a ride between buildings with the windows open and see how obnoxious it sounds. I used to get is that a Cadillac look from people standing on the side walk.After a month of using their loaner that started with 12 miles they called and said there is nothing they can do as the warranty expired by years not miles and no longer covered. I solved the problem that same week as I traded it in and GM has lost a long time customer once again. I went through the car with electronic sound equipment and i believe that due to the short skirts on the light weight pistons they are rattling in the cylinder walls and due to the cast nature of the block the sound is being magnified.Should not be for the price they charge when new but Cadillac is not an owners car it should be lease only 3 years and out, headache gone and start over.Good luck but I would be bailing out asap unless you have extended warranty. I did like my car but it was worse than my Corvette experience.Never again GM!!!