yes, i know there's plenty to read about the topic in a search, but everyone is asking about older cars. here's my scenario. 2003 z06. just under 17k miles. engine is completely stock. 10w30 synthetic in it with 3k miles on it (time for a change?). display said it was 81 degrees outside. at around 55-65 mph in 6th gear, under somewhat heavy load (half throttle, slightly uphill), i could hear pinging. the gas is the same 91 octane from the shell station ive been going to since i got the car. i used to be into f150 lightnings, and pinging one time was all it took to blow those engines, so im paranoid. this shouldnt be happening at only 17k miles . any ideas on how to take care of this?

 

1st off I never run 91 octane, only 93.

2nd hard accelleration in 6th @ 55mph... no such thing down shift too low RPM's.

I would run 93 octane and a good cleaner and open it up in the RPM's to clear out the carbon and see if it goes away.

 

Southern California... 91's the best I can get. For what it's worth, I always try to go with either Shell or Chevron. And it wasn't hard acceleration. I was in no hurry, so when I shifted into 6th it fell to about 1500rpm. I gave it some more gas to (slowly) bring up the speed a little. That's when it started pinging. Should I run some seafoam through the fuel system?

 

During the summer I see high daytime temperatures above 96 degrees. At around 1500-1800 rpm in 6th, I will also get some pinging. On my last dyno, we set the timing back alittle, and it helped. The dyno room temp was well over 100 degrees.
I ran across this article, it seems you and I aren't the only ones, as where I live we can only get 91 octane, but this article helped explain why its happening.
I am going to try adding some torco additive during the hot summer months, as when it cools off, the pinging goes away.

http://www.idavette.net/hib/fuel/page2.htm

 

Cant get 93 octane here in California as 91 is it.

I NEVER drive in 6th gear UNLESS its a flat long road and even then probably not. In fact I don think my car has ever been in 6th gear in the last 20K miles. Anything even on the lightest uphill shoudn't ever be in 6th pinging at 1500-1800 rpms unless you just wanna drive like a 85 year old lady..I mean why the heck do that? Trying to save gas?

I'm always in 5th on freeways with traffic or without and I never have my engine at ANY rpms under 2K no matter where I'm driving or what road I'm on.

If it pings at a low rpm then shift down....Its not rocket science here people!

On 100 degree days running 91 octane I have never pinged and I drive the living hell out of my Z06.

 

I shift into 6th @ 42-43mph, and never have pinging issues... it could have something to do with all the torque I have, and my tune, but it does save me a huge amount of gas each week. In my camaro, I had to be 53+ to put in in 6th with out pinging.

 

I doubt it's pinging... these cars make sewing machine noises and you can hear exhaust pulses in the manifolds due to the position of the motor in the car and the relative lack of sound deadening.

So many on these forums complain about pinging... that's what your knock sensors are there for.

 

Unless you have a DTC set showing a problem with the knock sensors, it is unkikely you are hearing a true knock.

Most people today don't know what a real knock sounds like since the engine computers reduce/eliminate it. Back in my "younger and less responsible days" a buddy of mine and I took his dad's Cadillac Eldorado over the "hills" to Santa Cruz. The engine was an 8.2 liter (yeah ... 500 cubic inch) monster that ran on premium fuel. On arrival in Santa Cruz we realized we didn't have enough fuel to get back home ... so scrounging around we came up with enough cash to put enough fuel in to get back ... but at "regular" prices ... not "premium" as the owner's manual said we needed.

The car sounded like a gang of iron workers were driving rivets into the engine block as we climbed back over the "hills" of Highway 17 .... not so bad on the downhill run into the bay area .... the iron workers went back to work on the flat run back to the house .... and when we got back to his house we couldn't shut down the engine. It was turned off but with the engine continuing to run on the diesel effect, and a carburetor feeding fuel to it (because a carb feeds fuel based on air flow) it took several minutes before the fuel pressure dropped enough to finally shut down the engine.

Needless to say, his dad was one PISSED OFF dude after our escapade. The only good news was that the fuel tank was so empty that a fill with Premium fuel quickly cleared the knock issue.

The point is, a knock is not some subtle change in engine note .... it really does sound like hammers being slammed against the engine block. If you have a knock you will know it. Anything less is managed by the engine computer.

 

The KR pulls out 5 degrees at high power settings. We saw this on the day I dynoed. It just doesn't take out one degree at a time. You could hear it detonating and then the kr pulled 5 degrees out. We lowered the timing a few degrees, it stopped and then dynoed fine. The lost in rwhp was around 8 rwhp when it pulled the 5 degrees. We did add a octane additive, and also did a run with it with the timing where it should be. So, thats why we saw what the lost was.
Yes, it is pinging, because as the temperature drops down to around 75 degrees, the pinging does go away.
If you read the article I posted, it does go into detail about this. Their are other articles and some call it coil dwell, due to the cam events at that RPM.
The pinging also stops when I put in an additive.
When my car was stock, I would only get this only on very hot days, i.e over 95 degrees. This is in agreement with the article I posted. I have been in DFW, got 93 octane, and have no problems. But now that my heads are milled, only to 62 cc's, and only have 91 octane, I get it around 85 degrees.
I do have friends that run 89 octane on their stock Z06's, and live in the same area, and never hear it. Of course their wives say they never listen anyway..........

 

I know the knocking sound very well. I have an old truck that used to do it like crazy uphill.

My 01 z06 knocks too. and it does not correct itself. I have to let off, or shift, then it will stop.

I also found the same thing with temps. I cant get it to do it in the 60's down. but above say 75 or more, it will knock sometimes randomly. I never had a knock in 6th, or 5th... all mine are in usually 1st or second going to redline. a couple of instances in 3rd

I once had it knock down hill in 75 degree's 1st gear full throttle on 91 octane and octane booster. I though maybe the booster was causing it since I never had it down hill.

I later filled the tank with 100 octane in the summer here 90+ degrees out and never got the car to detonate beating it senselessly.

 

Octane booster.... That stuff is a joke.

 

I have been recently getting knock under wide open throttle, but not on a regular basis. I have tried octane booster as well with little to no change.
I am not getting any codes or anything. My tune has been in the car for over a year now, my tuner suggested I change my fuel filter before we go into looking at the tune. I only have 28k on the car.
I went to replace filter only to find that my cars filter is in the tank
I have also been hearing odd noises coming from what I believe is the fuel pump. Not sure if it's a clogged filter causing the pump to complain about it, or if it's all due to the pump.
I know for a fact that I've had knocking, so why wouldn't the car be showing a code?

 

right you are!

 

There is no code for knock. There are codes the PCM can set if it thinks the knock sensors are bad, (P0325, P0327 or P0332) but a knock will not set a code. The diagnostics for a knock are basically as follows ...

Check PCM for Knock Retard - can be anywhere from 0 to 16 degrees of retard

Test for correct fuel pressure

Test for contaminated/alcohol in fuel

Check Long Term Fuel Trim (near 23 percent is too high)

Check heat range of spark plugs

Check engine cooling system for performance

Check engine for oil in combustion chambers (excessive oil consumption) - leaking valve seals

Check cylinder compression - excess carbon buildup in combustion chambers

Check (automatic) for TCC proper operation - Applying TCC too soon can cause knock.

If you're running some other brand/type of plug ... try switching to the AC Delco 41-985 that are pre-gapped (correctly) at .040 maybe that will help.

 

Thanks for the info

I read on the internet last night that there are 2 fuel pumps, 1 constantly pumping from right tank to the left tank and that it operates silently, and the other is in the left tank and can be noisy, but is not an indication of pump failure. The information stated that there was a tech.service bulletin about this issue from GM.
Anyone heard of that?

 

Don't know about the TSB ... maybe someone else can locate that.

There are two "pumps" ... but they are different ....

The car has two fuel tanks ... Left and Right. When you fill the car the fuel fills the left tank and then flows across and fills the right tank. When you start the engine, the electric fuel pump in the left tank feeds fuel to the engine. Just after the fuel line leaves the electric pump there is a "T" fitting that routes a flow of pressurized fuel to the right tank. In the right tank that fuel flows through a siphon pump and then flows back to the left tank along with fuel picked up by the siphon effect. As you drive the right tank is slowly drained and the left tank is the feed tank for the engine.

That's why the right "pump" is silent, and theoreticcally never needs service as it has no moving parts in it.

 

Can you interogate the ECU for this information through the DIC, or do you need tuning software to check it?

The Long Term Fuel Trim is an interesting possibility indicating something is basically wrong with the tune.

 

Unfortunately you cannot display parameters like LTFT on the DIC. You will need tuning software to read it. Check, not all of the "tuners" can read some parameters. Some of the cheaper scanners can't report items like LTFT.

 

 

It's over 100 every day here and all I get is 91 octane. I can use 6th down to 40mph without knock but if I accelerate I have to be real gentle with the throttle. I also notice a very, very slight knock at WOT sometimes, but for the most part it's amazing how well my car handles low RPM, high load operation under high temps.