Pinging Only at High RPM Load

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Feb 3, 2006
My 2003 GMC Sierra 5.3L with 161,000 of my miles, runs great, but pings loud only in process of reving on the way up towards high RPM's.

This only happens with 87 Octane, as what is the standard rating to use.

If I put in 92 Octane or 92 Octane with no Ethanol, it does not ping under the same conditions.

What is causing that and what can be done to eliminate it?

Re-program at the dealer? Something else?

Good ones. I have run Amsoil P.I and Techron at high concentrations recently.

It ping at the very next tank when I go back to 87 octane.

Perhaps I should pour a little Seafoam in the power brake booster to clean up more carbon?
i was gonna say you knock sensor may not be working at 100%. i know that my 02 8.1 chevy will ping a little as i start off from a stop light, its a six speed manual. if i use a higher octane gas it seems to be a little better, but i would run some sea foam through it first, both in gas and oil and go from there.
Oh, I also put in a can of Engine Restorer in the oil about 4,000 miles ago.
GM makes a product called AC Delco combustion chamber cleaner.

Regardless, you shouldn't have very audible pinging if the knock sensor is doing its job.
My mom's 1999 CRV and 2002 Toyota Solara 2.4 always pinged at full throttle at 4000 RPM and above. All cars were run with 87 octane gas because the owner's manual stated that is what should be used.

The fuel was occasionally treated with Techron, but the intake manifold didn't get Seafoam treatment.
The EGR valve is out of the equation at full throttle.
If you rely on the knock sensor to fix this, you need more octane anyway - it is much better to use the octane you need, then have the KS yank timing.
I'd try trickling/misting water in the intake while keeping the engine running at 2,000 RPMs.
Possibly you're getting "sensitive gas", whatever they call it, where the motor octane and research don't jive with your high speed operation. IIRC, motor is the high speed test. Might even be a different brand that'll work better-- generally only if you live somewhere with several refineries/pipelines etc.

On my saturns the car ignores the knock sensor by programming above a certain RPM. With the oil burning I've gotten an occasional high-rpm ping but quickly clears itself out.

I like the water mist idea!!
Thanks! I will trickle water or seafoam in the power brake booster first while using the 87 Octane and see what happens.

One thought I have: Since I frequently use 100% gas 92 Octane, perhaps the engine system learned to run on that gas and when I put in the 87, it's not enough?
It is possible; GM likes to wring every last bit out of the gas that goes through their motors.

On my saturns at least, one "good knock" at lower RPM (due to a burp of burning oil) would make 'em doggy for the next 200 miles... so damaging knocks I would assume are well controlled on your truck... and quickly learnt.
OK. My 96 Merc did the same thing for two years. Finally a friend told me to clean the MAF sensor. I did that and no more ping. That was last Nov. and it's been fine ever since.
Google, cleaning MAF sensor,. That may help. Also you will find a slight increase in MPG.
Here's the wrap up...

I slowly poured Seafoam in the Power Brake Booster hose, let sit 10 minutes, started up & ran it hard.

The pinging is now gone!

Glad you got it worked out.

One other thing I thought I'd throw out there.

Pretty much all ECU's now days are adaptive to driving styles and conditions. A good amount of the time this is the reason that you get some pinging when you go from a tank of 92 octane to a tank of 87.

When you're running the 92 the adaptive programming can increas the timing a little to give you a little better power without pinging. It'll advance it until the knock sensor detects detonation and then back it off until it doesn't happen anymore.

Then you fill up with 87 but the ECU is still adapted to the 92. So you will sometimes hear some pinging for a little bit after the fill up until the ECU adapts and backs the timing back down for the 87.

If the knock sensor isn't working up to par it can take longer for the ECU to adapt, therefore you hear the pinging longer than you should.

From my experiences, if the vehicle specs say to run 87, you can run mid grade (89 or 91 depending on where you live) and the ECU will bump the timing a little and give you a little extra power. With high octane (usually 93) the ecu won't bump the timing anymore than it will with 89 so it's kind of a waste.

Throw a can of B12 Chemtool in the gas tank and start running mid grade and I'll bet all pinging will stay away and you'll get a little power bump.
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