pinging or timing chain?

[Spykem4e]

Hi guys,

Since its been very hot and humid in montreal for the couple of weeks now, my car, when I accelerate but only lightly, you can here a rattle like pinging or timing chain grinding trrrrr like metal sound coming from the engine compartment.

the sound only occurs when there's a very small load on the engine. When I hear it, i just have to press a little bit more the gas pedal and the sound disappear. It only does that sometimes. I don't loose any power from the engine when this occurs. I don't know how to describe the sound but its not like a metal ball in a can. ts like a trrrrt trrrrt (you should see me in front of my computer trying to do the sound LOL)

If it was the timing chains (because I have 3), what would happen if one or 2 or 3 was stretched? Would the car runs okay?

On idle, no sound. Idle + reving, no sound.
Half throttle or full throttle, no sound.

and btw, the car is a 2005 cadillac cts 3.6l vv6 114k miles

tks. Mark!

 

[tig1]

Pre ingnition

 

[ARCOgraphite]

What grade fuel? I would almost guarantee ping. Most folks dont use their engine enough to keep it de-carboned. Italian Tune-up: "I try to do three Full throttle 3rd gear run-ups from 3500-5500 rpm a couple time a week at least (on the Expressway)". Stop light jackrabbit driving in the lower gears just places undue stress on the drivetrain, and does not de-carbon as well.

 

[Familyguy]

Originally Posted By: Spykem4e
Hi guys,

Since its been very hot and humid in montreal for the couple of weeks now, my car, when I accelerate but only lightly, you can here a rattle like pinging or timing chain grinding trrrrr like metal sound coming from the engine compartment.

the sound only occurs when there's a very small load on the engine. When I hear it, i just have to press a little bit more the gas pedal and the sound disappear. It only does that sometimes. I don't loose any power from the engine when this occurs. I don't know how to describe the sound but its not like a metal ball in a can. ts like a trrrrt trrrrt (you should see me in front of my computer trying to do the sound LOL)

If it was the timing chains (because I have 3), what would happen if one or 2 or 3 was stretched? Would the car runs okay?

On idle, no sound. Idle + reving, no sound.
Half throttle or full throttle, no sound.

and btw, the car is a 2005 cadillac cts 3.6l vv6 114k miles

tks. Mark!


Next time you gas up, use premium. I suspect that will deal with your pre-ignition issue. I'm not sure if that engine has a knock sensor, but that should trigger the ECU to retard the timing when it detects knocking/pinging.

Good luck.

 

[ARCOgraphite]

Originally Posted By: tig1
Pre ingnition
Ping is typically a post-ignition event. I think Pre-ignition used to be called "run-on". Haven't seen this in a dogs age since electronic fuel injection makes this impossible. No fuel - no burn. Use to get run on on those Chrysler Cordoba with the "lean-burn" 360 and 318 in the early 70's.

 

[ARCOgraphite]

Originally Posted By: Familyguy
Originally Posted By: Spykem4e
Hi guys,

Since its been very hot and humid in montreal for the couple of weeks now, my car, when I accelerate but only lightly, you can here a rattle like pinging or timing chain grinding trrrrr like metal sound coming from the engine compartment.

the sound only occurs when there's a very small load on the engine. When I hear it, i just have to press a little bit more the gas pedal and the sound disappear. It only does that sometimes. I don't loose any power from the engine when this occurs. I don't know how to describe the sound but its not like a metal ball in a can. ts like a trrrrt trrrrt (you should see me in front of my computer trying to do the sound LOL)

If it was the timing chains (because I have 3), what would happen if one or 2 or 3 was stretched? Would the car runs okay?

On idle, no sound. Idle + reving, no sound.
Half throttle or full throttle, no sound.

and btw, the car is a 2005 cadillac cts 3.6l vv6 114k miles

tks. Mark!


Next time you gas up, use premium. I suspect that will deal with your pre-ignition issue. I'm not sure if that engine has a knock sensor, but that should trigger the ECU to retard the timing when it detects knocking/pinging.

Good luck.
+1. I would assume this is a prem fuel motor. A high output v6.

 

[ZZman]

I agree. Try premium fuel and see if it goes away.

You could also try some good fuel system cleaner like Gumout Regane, Chevron Techron or Redline S-1 in case it is a carbon deposit issue.

 

[AdRock]

Originally Posted By: ARCOgraphite
Originally Posted By: tig1
Pre ingnition
Ping is typically a post-ignition event. I think Pre-ignition used to be called "run-on". Haven't seen this in a dogs age since electronic fuel injection makes this impossible. No fuel - no burn. Use to get run on on those Chrysler Cordoba with the "lean-burn" 360 and 318 in the early 70's.


No, the pinging is a PRE ignition event. The ignition of the air/fuel happens too soon and the rising piston is now fighting the force of combustion. The pinging noise is the piston slapping back and forth against the cylinder walls.

 

[The_Jeff]

GM likes to run on the ragged edge of timing. Owners manual even says a little ping under light load is okay.

A timing chain (had a couple of bum ones) makes the same noise regardless of load, but varies/increases with RPM.

 

[Warstud]

Try using a different gas first and see if that helps. I had pinging in my truck with Shell and Mobil then I switched to Citgo and the pinging went away.

 

[Spykem4e]

Tks guys for the quick replies!

The manual calls for regular 87 but premium if towing for better performance almost like all gm owners manual says.

I'll try the Italian tune-up with some WOT + premium fuel. I also have a fuel/injector cleaner from GM in my trunk, I'll drop that in the tank too.

Weird thing is without the a/c, it doesn't ping. With the a/c, it pings sometimes. Those engine are suppose to have knock sensors.. how does it work?

Thanks again!

 

[ARCOgraphite]

Originally Posted By: AdRock
Originally Posted By: ARCOgraphite
Originally Posted By: tig1
Pre ingnition
Ping is typically a post-ignition event. I think Pre-ignition used to be called "run-on". Haven't seen this in a dogs age since electronic fuel injection makes this impossible. No fuel - no burn. Use to get run on on those Chrysler Cordoba with the "lean-burn" 360 and 318 in the early 70's.


No, the pinging is a PRE ignition event. The ignition of the air/fuel happens too soon and the rising piston is now fighting the force of combustion. The pinging noise is the piston slapping back and forth against the cylinder walls.
I disagree. Pinging is uncontrolled combustion of CC end mixture AFTER the spark ignition event. It can be cause by low octane or CC hot spots. I built many a HC BB chevy race/boat motor, dealt with CC and dome shaping and plug phasing.

 

[ARCOgraphite]

Originally Posted By: Spykem4e
Tks guys for the quick replies!

The manual calls for regular 87 but premium if towing for better performance almost like all gm owners manual says.

I'll try the Italian tune-up with some WOT + premium fuel. I also have a fuel/injector cleaner from GM in my trunk, I'll drop that in the tank too.

Weird thing is without the a/c, it doesn't ping. With the a/c, it pings sometimes. Those engine are suppose to have knock sensors.. how does it work?

Thanks again!
Ping is not hard knock. Othewise you would have a "ping" sensor. Most state-of-tune allow light ping. OTW your timing map will be too conservative for good gas milage and throttle response. Gas is poor in my town this year - may be an epidemic.

 

[mechtech2]

Pinging is a POST ignition event.
That is why advancing the timing causes pinging.
AFTER the spark ignites the mixture, it may be too early and have peak pressure before TDC, and spark knock.

But concerning the original problem, try the highest octane that you can get - not a mix of old 87 and new 93, but a full tank of 93.
If it goes away, you know it is not a mechanical knock.
Sure wish we could hear it.
An EGR system that is faulty can cause part throttle spark knock, BTW.

 

[ARCOgraphite]

Originally Posted By: mechtech2
Pinging is a POST ignition event.
That is why advancing the timing causes pinging.
AFTER the spark ignites the mixture, it may be too early and have peak pressure before TDC, and spark knock.

But concerning the original problem, try the highest octane that you can get - not a mix of old 87 and new 93, but a full tank of 93.
If it goes away, you know it is not a mechanical knock.
Sure wish we could hear it.
An EGR system that is faulty can cause part throttle spark knock, BTW.
+1 mechtech2, ADROCK is posting erroneous information. Good info on the EGR system too.

 

[Spykem4e]

I'll try 2 full tanks of premium 93 octane + fuel injector cleaner from GM.

Concerning the EGR, I've read on the 3.6l vvt in 2005 that it doesn't have any EGR.. maybe I'm wrong but I just wanted to let you know.

Could it be the pcv system that is inside the valve cover working very hard?

P.S: I tried to take a video while I was driving but you couldn't hear a thing. I'm sad!

 

[ARCOgraphite]

Originally Posted By: Spykem4e


Concerning the EGR, I've read on the 3.6l vvt in 2005 that it doesn't have any EGR.. maybe I'm wrong but I just wanted to let you know.

EGR could be through cam phasing, typ with VVT. Life in the world of high performance engine tune - not a big deal - worry when you get KNOCK. And beat the thing some on the highway! Italian Tuneup!

 

[BuickGN]

Originally Posted By: ARCOgraphite
Originally Posted By: mechtech2
Pinging is a POST ignition event.
That is why advancing the timing causes pinging.
AFTER the spark ignites the mixture, it may be too early and have peak pressure before TDC, and spark knock.

But concerning the original problem, try the highest octane that you can get - not a mix of old 87 and new 93, but a full tank of 93.
If it goes away, you know it is not a mechanical knock.
Sure wish we could hear it.
An EGR system that is faulty can cause part throttle spark knock, BTW.
+1 mechtech2, ADROCK is posting erroneous information. Good info on the EGR system too.


Pinging can be pre or post ignition. Ping is a noise, not an event. Many things can cause the noise, like preignition and detonation.

I'm too familiar with detonation. I've experienced it from too much boost and from too much timing. Too much boost causes preignition and a ping. Too much timing also causes a ping. Both will kill parts.

 

[oilyriser]

Could be as simple as a loose heat shield touching the exhaust pipe as the motor mounts flex.

 

[Spykem4e]

heat shield? hmm...

The sound does happen only in 2nd and 3rd gear. The 1st gear is geared too low so at 10km/h, the car shifts in 2nd. But in 2nd gear, you can hear the kinda rattle sound just when its going to shift from 2nd to 3rd gear. Same happens when the transmission will shift from 3rd to 4th.

It doesn't happen all the time but when the windows are closed, its coming from the back of the center of the dashboard. When all windows are down, you can hear it too but this time, it looks like its coming from underneath the car.

Its driving me nuts!