I have replaced the plenum gasket with a plate in my 135k mile 5.9, along with a 180 tstat change and following up with a Seafoam cleaning. No codes being thrown. Doesnt seem to matter what brand of fuel I run, once the temp reaches 170-180, I still have some ping above 2500 rpm with moderate acceleration and up, or at low rpms in OD with a load.Its not the worst ping, but its annoying enough. Power is great and Hemifever provided me with a less aggressive 91 tune, but still have the ping. Octane booster isn't really a help. Any other ideas on a cure? Don't really want to use the 89 tune and give away low end torque unless I have to. I have 3923 plugs in it, along with a new MAP and ICS sensors. Additionally, the problem seems to manifest after its shut off and heat soaked for a bit while sitting when parked.

 

The pinging is a timing or fuel issue. Since you tried the fuel (all types) you are going to have to adjust your timing. If you run it like that, you take a chance of serious engine failure. It is not just annoying it can be catastrophic. Just a heads up. I would hate to see you burn a hole in a piston and loose compression. Then you have to rebuild an engine. Big price to pay for a little more power.

Disclaimer, I'm new. Sharing experiences outside of this thread.

 

Do you have a cold air intake? Try to get the coolest air possible. If you shorten the gap on the spark plugs it may help slightly by cooling the spark a little. Also check your injector timing, if its off to much fuel can puddle on top of hot intake valves and drip into the cylinder instead of the piston sucking in fuel mist during the intake stroke.

 

agreed on the timing thing. I run a 94 tune (33 degrees of timing) in my V6 with 91 gas and I get just a little bit of ping, goes completely away on 93. But you may have less leakdown than I do, among other considerations.

Did you pull the seafoam through the vacuum lines, gas tank, or oil?

 

Just want to clarify that I'm well aware of what detonation can do to pistons and ring lands.

Took a look at the coolant last night and it was quite heavily mixed with mainly coolant. To experiment, I drained some of the coolant and added distilled water and water wetter back in in an effort to see if it will displace some of the cylinder head heat anymore. On my 30 mile ride into work this morning, it was 60 degrees out. I never heard one audible ping. I guess we will see what it does on the way home this afternoon to see if it has more to do with ambient temperature than coolant. My feeling is the latter.

Would hate to step back to the 89 tune. Just doesn't feel like as much torque management is removed.

 

Well the ping is still there during the afternoon heat. Mainly under load and upon more than moderate acceleration or after heat soaking. Considering such a stark difference between performance of different times of day, should I be looking towards the IAT or CTS? How about slightly opening the plug gap?

In the meantime, I went back to the 89 tune.

 

It should be pulling timing and fuel with engine heat instead of rolling it in...I think...

You have a 180 thermostat yes?

 

You might what to check your spark plugs. Make sure they are the right heat range.
If they are you might try a cooler one.

 

Yes, 180 tstat and running 3923 autolites.

Picked up a new intake air temp sensor. Seems probable as a cause given the conditions.