4.6 pinging
 

I have a '96 GT, it has a Borla cat-back and K&N filter, otherwise stock...
It has been pinging on any fuel lower than 91 octane. The manual says it should run on 87, what gives?

I had heard I may have carbon build up on the piston and valves causing pre-ignition and that I could use a "combustion chamber clear", the kind you suck in thru a vacuum hose, not "fuel injector cleaner" that you add to the gas tank.

Any advice would be greatly appreciated, thanks

Rich

How many miles on your car?

It is not uncommon for high mileage cars to ping and need high octane due to the condition that you described. I think you are right on the money with your assesment.

I wish I had better news...I don't know any other way to clean it than to pull the motor apart.

Do you have a performance chip? Perhaps the timing is advanced to much?

Mileage is 70K
No performance chip, so ignition timing should be OK. Only cat-back exhaust and K&N filter (which I recently cleaned)

I've been asking around at some autoparts stores...the guys have 'heard' stories about pouring tranny fluid or water into the intake to clean out the combustion chamber.
Obviously when I say 'pour', you have to do it at a controlled rate or the motor will hydro-lock and bend a rod...

The water makes sense because I once had a head gasket leak (coolant into cylinder) on a 4-cyl, after taking the head off, the cylinder which had the coolant misting into it was shiny clean...the others were black with carbon. So the water flashing to steam may blast the carbon off.

Thanks in advance,
Rich

since you just cleaned the k&n try and clean the wires in the maf sensor cause the oil from the k&n will stick to them and cause dirt to stick as well so it will need read right

clean them with either elec. contact cleaner or brake cleaner(non colar.)
before spray them from 8-12 in. away and dont go full blast on them and let it dry and see if that helps

96's had cooling problems with the GT and Cobra...if your car is running hot, you may experience some pinging. My neighbor swapped a 98 cooling fan/shroud and radiator and now the car runs fine. Just a thought...

Sorry most of my knowledge is in the F-body. But anyways I had a 91 Z28 and it did the same thing, go down to an autoparts store and get some stuff called Sea Foam along with that get a peice of hose about a foot long and that is the same size as a vacuum line going into the intake. Undo a vacuum line off the intake and plug the new hose into the port and lightly suck the sea foam into the intake. The car is going to smoke like no other. And it will smoke for a while, just when you think its never going to stop wait longer and it will stop smoking. Also to the previous reply definately clean the MAF with electrical contact cleaner. DONT touch the wires with anything but the spray from the can and gently at that.