Engine P:inging when Hot.

[Mercury Rising]

Greetings,

I have an issue where the engine is running normally when cold, but when it gets hot it will ping, which is quite noticable under load. I tried premium gas and this seemed to help a little. I was wondering if it could be caused by a bad spark plug. I have had the car for 2 years or so and I don't know when they were last changed. Would this be a good place to start? I will also check the codes when I have time. I did try adjusting the timing but I had difficulty seeing the marks on the harmonic balancer so I just kind of left it where it seemed happy. (The pinging started before I did this.)

Thanks guys.

PS - I had a profile here a year or so ago but I lost it so I'm back with this one. I'm the weirdo that flushed his engine out with transmission fluid if you remember that!

[86VickyLX]

Change the plugs. Go from there. The pinging sounds like it might be carbon buildup in the engine. Verify you have the correct timing as well. Get under the car and clean the balancer so you can see the marks. Paint on some white out at 10btdc and set it there with the spout connector disconnected.

I'd scan it for codes and see what's going on there as well.

[87_crown_vic]

i set mine for 12*

[85crownHPP]

PS - I had a profile here a year or so ago but I lost it so I'm back with this one. I'm the weirdo that flushed his engine out with transmission fluid if you remember that!

I do that too!

Is it a CFI car? Mine pinged even with premium gas and the timing retarded.

[88grandmarq]

Knowing some specific information about your car would be helpful, simply telling us what year it is will narrow down if its a CFI or EFI engine. I would suggest updating your signature with vehicle information.

Pinging can be caused my many different things. The most common are; lean fuel mixture, worn engine causing carbon build up on tops of pistons, ignition timing is set incorrectly and wrong heat range on spark plugs.

the first thing I would suggest is doing normal maintenance, that way you have a fresh place to start and some common issues are eliminated. do a full tune up on the car and replace; distributor cap, rotor, wires and plugs. also replace the fuel filter, PCV valve and thermostat. make sure the coolant is full and change the engine oil.

[Crownvicman289]

Judging by his pic, it appears to be CFI. I'm going to jump on the excessive carbon buildup bandwagon. If you want a real left field answer, check your IAT sensor. Mine from my donor was covered in oil and surely affecting its reading. As IAT's rise, the EEC is supposed to pull timing at a certain point. If it's covered in oil and not reading correctly, that can't happen. I'd try cleaning all the carbon out first though and re-verifying your base timing.

[91waggin]

Uhm....EGR stuck open/opening at wrong times? I thought that was pretty much the leading cause of ping on these cars.

[gadget73]

cooling system in poor condition can also contribute if the engine is running too hot. Thats another very very common story, clogged radiator, weak fan clutch, etc.

[Mercury Rising]

Thanks for all your replies.

It's a 1986 Grand Marquis 5.0 EFI. I recently replaced the entire cooling system, except for the heater core which I flushed and found to be clean. The engine has a very slight knock on startup but otherwise runs like a champ.

I will change the spark plugs, PCV and ECV valves as soon as I can manage, because I have another problem that the car doesn't like to start when hot, and I suspect the ECV is responsible.
What is the best way to clean carbon, I heard that you can spray a SMALL amount of water at the intake. I regularly add Lucas fuel additive and / or mystery oil to the gas.

[gadget73]

Change the fuel filter too.


ECV ? Not an acronym I'm familiar with. Every book calls parts by a different name though.

seafoam or a comparable product through the pcv valve is one way to do it, or just misting water through the intake will do it too. Water is cheaper. Just be sure to mist it, not dump it straight in.

[Mercury Rising]

My mistake, I use the ECV acronym at work and it's stuck in my head, doh! I'm going to try the misting thing. I changed the fuel filter when I got the car. I would also like to change the fuel lines under the intake plenum, but I'm not sure what size they are. I suspect that there was a slow leak from one of them in the past, but it seems to have healed by itself. I could tell because there would be a gas smell from that area.

Thanks!

[85crownHPP]

The fuel rails don't go bad... you may have a leaky injector O-ring. Replacing the vacuum lines that feed under the plenum is a good idea though, but not likely the cause of your problem.
Are you sure its not overheating? That will make it ping, and the dummy light doesn't come on until its hot hot. I blew a heater hose once and it started pinging before the light came on...

[Mercury Rising]

Nice idea, but it doesn't show any other signs of overheating at all, and I recently replaced the water pump, thermostat, radiator, belts n hoses. I check the oil / coolant at least 2 times a week.

[86VickyLX]

Have you checked your vacuum lines? To make sure you didn't have any leaks?

[Mercury Rising]

Just an update to this thread, I have since replaced the spark plugs, distributor cap, and rotor this helped somewhat. Then i replaced the EGR valve and EGR position sensor, and the pinging has stopped. The car seems more powerful than before. I have a new issue, however, which is that the engine stumbles at low low throttle, IE parking lot speed. Idle is fine! But that will be for another day. Also replaced master brake cylinder.