Excess Pre-ignition in My '05 GT

[RCSnyder]

I suppose any pre-ignition is excessive, but Pressing and holding the loud pedal comes with more than I'd certainly like.

Running the best gas and brands I can around here, but the 91 octane doesn't seem to be enough.

No codes, just too much ping.

PCM replaced a while back, and don't think I got unintended performance upgrade, so...

Thoughts?

Thanks in advance

Bob in Liberty MO

[ptcruisersteve]

Carbon buildup in the cylinders?

[RCSnyder]

Could be, I guess.

Fuel additive or something simple to alleviate?

Thanks in advance.

Bob in Liberty MO

[ptcruisersteve]

Originally Posted by RCSnyder

Could be, I guess.

Fuel additive or something simple to alleviate?

Thanks in advance.

Bob in Liberty MO

What about the water clean method using controlled amount through the intake system?

[pdbrains]

You need to get a scanner that can read your ignition timing and see if there is any LT knock retard going on. Maybe knock sensor is not working. I would take a look at you spark plugs and see how they are running. Maybe your lean or running too hot.

[Handy_Cruiser]

Originally Posted by pdbrains

You need to get a scanner that can read your ignition timing and see if there is any LT knock retard going on. Maybe knock sensor is not working. I would take a look at you spark plugs and see how they are running. Maybe your lean or running too hot.

This and Steve's advice are very good.

If I had no trouble codes indicating the problem, I'd start with Steve's advise and try an additive to remove carbon build up. I wouldn't try the "water method" because that has been known to crack valves in some engines. A good additive in the fuel and/or directly into the throttle body via a vacuum port might do the job. I would try to some HEAT additive as well in case there is water in your tank. To be exact, my normal first step to engine miss-fires and pinging is often a bottle of heat and a bottle of cheap red-bottle STP fuel treatment. That often solve a contaminated fuel issue.

If that didn't work, a shop-level OBDII scanner would be the way to go. With that, you can look at the air/fuel ratio, knock sensor and timing, and the PCM's attempts to adjust them. A timing issue might be a functional but weak crankshaft sensor and/or the leads going to it. Fuel issues might be a weak fuel injector or a weak or clogged fuel pump making the engine run too lean under load. If you have no codes, a weak or clogged fuel pump is likely the highest probably. Shop-levels scanners are pretty expensive and usually not needed for most DIY work except in scenarios like this. So an hour of time at a good shop might be in order.

[RCSnyder]

I ran two consecutive tanks full with Sea Foam added and the knocking has cleared. Thanks to all.

[ptcruisersteve]

Originally Posted by RCSnyder

I ran two consecutive tanks full with Sea Foam added and the knocking has cleared. Thanks to all.

Thanks for letting us know what fixed the problem. Enjoy your Pt Cruiser.