l purchased this car new in 99,it pinged from day one,mainly going up hills during hot weather ,the dealer where l bought this automobile from said its normal,,,but7 years later it gets worse every year, and it does this most of time in any temperatures or conditions, l have tried different fuels,,nothing helps or changes,,any ideas here, other than bringing it in and having them charge me 500.00 for diagnois..???

Use higher octane fuel! Using a water injection system sometimes helps, but be sure to use only distilled (or rain) water or the mineral content of tap water will contaminate your engine.
Have you checked the timing? It may be too advanced!

sounds like a timing belt

Change brands of oil and use a heavier one.If you use 5W30 try 10W40 in warm weather.
On my new trucks first oil change l used Mobile 1 and it started pinging when towing and going uphill.
On the next oil change l used Valvoline and it went away.
Premium or mid grade fuel might also help.

Check the timing and use a higher Octane fuel. that should get rid of your engine ping..or knock as its called....

There is pinging & there is heavy detonation which sounds like a rod knocking & is caused by either old bad gas or heavy carbon buildup caused by oil burning in the cylinder.

Yours is probably caused by bad timing marks. Try to road tune it by setting the timing back a couple of degrees at a time, then test drive it.

The water injection mentioned can help, but even better is Alcohol injection. You can find these kits online or at Ebay & they can be used for water or alcohol., even a mix.

It is diffently running to lean, computer programing & bigger injectors may help.

Good luck

Switch to 93 octane, and the pinging will stop.

Cheap fuel, engine running too hot, or your egr valve or sensors for it are not working correctly

Listen, Try this, There is a little grey plug it is called a shorting bar for the octane . Over next to the air box l believe u will find it. l know there will be a green wire & l think the other is grey. 2 wires is all that goes to it. Simply unplug it & drive the car & see if it is gone. Should do the trick, just leave it out. This is for Ford Techs but it is so simple that anyone can do it. If it has gotton worse then the EGR ports probley need cleaning as well. A good mechanic can do this. It is not for any average person to try.

Octane Octane Octane Not 87 at three different stations try 91 or 93 here in Texas and see. Other things that cause Ping. poor EGR flow, overly advanced timing. Lean running due to clogged fuel filter. Thermostat not opening enough hot running engine. And something you cannot fix poor combustion chamber design. 1999 cars have computers that read out live data a Technician worth his salt can tell you a lot looking at fuel trims.

timing is toooooooo advanced

timing belt

Its really sad how most people do not listen you have already tried different gas and that car should run on 87 octane you should not have to use anything higher. The only answer that sound close to a possibility is JOSH but l hate to tell you l had a 93 Ford Aerostar and nothing solved the problem something is probably wrong internal its to bad mechanics are not what they use to be if the computer do not tell them what to do they are lost, good luck.