Troubleshooting engine pinging

[alvocado]

After replacing a bad wheel hub assembly last night which was making a lot of noise, I noticed that I'm now getting some engine pinging. It is most noticeable at low RPMs (1000-1500) and under load (going up hill, etc.) It's pretty constant regardless of the engine being cold or warm. I've read a lot of the discussions and in lieu of starting down a path of endless cleaning and part replacement, I'm hoping to get some guidance on troubleshooting steps. The truck is an 02 Yukon Denali 6.0L w/73k miles. I cleaned the TBI in place about a year ago, new air filter and fuel filter installed last month, and no oil consumption. Any thoughts?

[kraig]

Knocks sensors.

[skills4lou]

What octane are you running? What does the OM call for?

[C & A s Dad]

You have likely read all the conversation concerning combustion chamber cleaning but the fact is if you have been using a fuel without good cleaning agents and maybe even if you have been using top tier fuel, you could have carbon built up in the combustion chambers. The more that carbon increases, the higher octane fuel that is required so the engine will not ping. The cheapest and easiest place to start is to run a pure Chevron Techron through it at the rate of 1 oz per 1 gallon. I would do this for at least 2 tanks and run them close to empty to get the full affect of the Techron. If this does not help at least some, your issue is likely not carbon and is a knock sensor issue. Some people wil try Seafoam and possibly even have the engine decarboned by a prof tech with prof equip such as Motor Vac or BGs. The prof cleaning will not hurt anything but typically if it is carbon you will see some improvement with the Techron. We sell a ton of it and hear some real success stories.

 

Regardless, the Techron is a wonderful product and will only help in cleaning the injectors and combustion chambers. It also is now formulated to help remove corrosion and protect the fuel gauge sensor.

[alvocado]

What octane are you running? What does the OM call for?

 

<{POST_SNAPBACK}>

 

 

 

I use 87 octane which is spec.

[C & A s Dad]

You may not want to run it permanently but you could try a tank of 93. If this helps it would lead me to believe you do have a carbon build up issue. If your Owner's Manual requires 87, your truck should run on it without pinging.

 

People we see in our stores with "pinging" issues will usually tell us that their car ran fine on 87 and then they started having to run 89 to keep the pinging away and in some cases they had to later begin running 91 or 93. This is when we usually sell them a bottle of Techron and explain what has happened.

 

Again, if it is a sensor issue, Techron is not going to help you, but what have you got to loose to try it?

 

Good luck.

[alvocado]

You may not want to run it permanently but you could try a tank of 93. If this helps it would lead me to believe you do have a carbon build up issue. If your Owner's Manual requires 87, your truck should run on it without pinging.

 

People we see in our stores with "pinging" issues will usually tell us that their car ran fine on 87 and then they started having to run 89 to keep the pinging away and in some cases they had to later begin running 91 or 93. This is when we usually sell them a bottle of Techron and explain what has happened.

 

Again, if it is a sensor issue, Techron is not going to help you, but what have you got to loose to try it?

 

Good luck.

 

<{POST_SNAPBACK}>

 

 

 

I'll give it a shot. I'll be ready for a fill-up by Friday so it would be a good time to run some cleaner through with a small amount of gas in the tank.

[alvocado]

GM-Tech: What steps would you take at the dealership to troubleshoot/correct this?

[GM-Tech]

GM-Tech: What steps would you take at the dealership to troubleshoot/correct this?

 

First step would be a road test to experience the condition and see if it's excessive. A little detonation under certain conditions is not abnormal.

 

Assuming this is not a normal detonation, I would do a snapshot of all the engine operating parameters when the knock is occuring. I'd then pour over all that data at my leisure when I was back at the shop.

 

Depending on what I see would determine my next steps. Are the knock sensors retarding the timing? What are the fuel trims as a lean condition could contribute to this problem. Is the EGR functioning properly? Is engine temp within norms?

 

If I see nothing abnormal in the engine operating parameters, I would question fuel octane/quality and carbon buildup. I'd probably go with a TEC (GM top eng. cleaner) soak overnight to see if that helps with a possible carbon issue.