Flat spot & ping

[Wheel7]

Hi all,

96 Crown Victoria LX W. Has a flat spot very similar to when an engine with carburetor would have a bad accelerator pump.
Pings under hard acceleration, when completely warmed up. Is worse with regular gas. Things I have done since it started: New fuel filter, autolite plugs from dealer, new Dorman manifold (for other reasons), inspected idle air valve, looks fairly clean, inspected pcv valves and hoses, cleaned MAF sensor with soft brush and liquid soap, rinsed thoroughly (helped some), have put Sea Foam and Lucas injector cleaner in gas at different times (didn't suck sea foam thru pcv valve). Also, 2 different Auto Zone stores would not run a scan for me because there is no check engine light. Is not driven sedately.
any other ideas?

[jimmytroanoke]

Originally Posted by Wheel7

Hi all,

96 Crown Victoria LX W. Has a flat spot very similar to when an engine with carburetor would have a bad accelerator pump.
Pings under hard acceleration, when completely warmed up. Is worse with regular gas. Things I have done since it started: New fuel filter, autolite plugs from dealer, new Dorman manifold (for other reasons), inspected idle air valve, looks fairly clean, inspected pcv valves and hoses, cleaned MAF sensor with soft brush and liquid soap, rinsed thoroughly (helped some), have put Sea Foam and Lucas injector cleaner in gas at different times (didn't suck sea foam thru pcv valve). Also, 2 different Auto Zone stores would not run a scan for me because there is no check engine light. Is not driven sedately.
any other ideas?

Pinging is quite commonly caused by lack of EGR function. - DPFE sensor, Stuck EGR Valve, or clogged EGR passages in manifold would be first places to look. Also could be a lean misfire condition. A good scan tool will tell you what your short and long term fuel trims are.