Q re. Chevy 04 5.3 1500 "dieseling" at 1750 RPM...

[cledford3]

Hi, I've had an ongoing issue with what my father referred to as "dieseling" (a diesel like sound coming from the motor) at around 1750 rpm in my 2004 Chevy 1500 5.3L, extended cab pickup. It is a weird issue - it happens regardless of the octane I use - but is inconsistent yet persistent. It appears between 1750 and 2k rpm but only when the engine is under moderate load (slight acceleration up say up a slight incline) when very slowly accelerating through that rpm range - if I'm on the gas I don't notice the noise at all. Due to the circumstances required it usually pops up when pulling away from a stop light in traffic, in a mall parking lot, or when traveling country roads with turns and slight ups and downs. Some times it lasts for several seconds, other times only for 1. It ALWAYS occurs when the engine is warm (it is not cold related).

 

After experimenting with a number of brands and octanes of gas I popped online to look up the problem and came across all kinds of scary information regarding the dreaded "piston slap" - although that seems to mostly be a cold start problem.

 

Please advise on what and how serious the problem may be - I would like to have a little heads up prior to taking it in for service. I have no problem taking GM to the mat on this – I’d just like to know how serious it may or may not be before getting started.

 

The other stats on my truck are:

 

- First owner - since August 2004. (one year on clock)

 

- 22K miles on the clock as of today - I commute a lot.

 

- Have changed the oil every 3-4500k (well under the oil usage monitor on the truck - usually around 50% of the stated oil life left) with Mobile 1 synthetic.

 

- Truck is 5.3 model extended cab LS 4x4 with "HD tow package" and gearing. (But does not say HD on it, not sure the difference)

 

Thanks for any and all help,

 

-Calvin

[2004GMC1500CC]

Hi, I've had an ongoing issue with what my father referred to as "dieseling" (a diesel like sound coming from the motor) at around 1750 rpm in my 2004 Chevy 1500 5.3L, extended cab pickup. It is a weird issue - it happens regardless of the octane I use - but is inconsistent yet persistent. It appears between 1750 and 2k rpm but only when the engine is under moderate load (slight acceleration up say up a slight incline) when very slowly accelerating through that rpm range - if I'm on the gas I don't notice the noise at all. Due to the circumstances required it usually pops up when pulling away from a stop light in traffic, in a mall parking lot, or when traveling country roads with turns and slight ups and downs. Some times it lasts for several seconds, other times only for 1. It ALWAYS occurs when the engine is warm (it is not cold related).

 

After experimenting with a number of brands and octanes of gas I popped online to look up the problem and came across all kinds of scary information regarding the dreaded "piston slap" - although that seems to mostly be a cold start problem.

 

Please advise on what and how serious the problem may be - I would like to have a little heads up prior to taking it in for service. I have no problem taking GM to the mat on this – I’d just like to know how serious it may or may not be before getting started.

 

The other stats on my truck are:

 

- First owner - since August 2004. (one year on clock)

 

- 22K miles on the clock as of today - I commute a lot.

 

- Have changed the oil every 3-4500k (well under the oil usage monitor on the truck - usually around 50% of the stated oil life left) with Mobile 1 synthetic.

 

- Truck is 5.3 model extended cab LS 4x4 with "HD tow package" and gearing. (But does not say HD on it, not sure the difference)

 

Thanks for any and all help,

 

-Calvin

 

<{POST_SNAPBACK}>

 

 

 

Seems that if it was spark knock, the knock sensor would pull timing and take care of it or the high octane gas would. Have you taken it to the dealer? Should be covered under warranty. May be as simple as something being loose and rattling at the resonant frequency.

[cledford3]

May be as simple as something being loose and rattling at the resonant frequency.

 

<{POST_SNAPBACK}>

 

 

 

 

It doesn't sound like something loose - it sounds like the motor changing to a different sound. I'm a little concerned about the dealer - and it coming back worse :/

 

-Calvin