Horrible Pinging

[anesthetize]

Hey guys, 04 Mach 1 w/ 56k miles, stock other than offroad xpipe, intake, catback.

The other day my car started pinging/knocking/predetonating horribly. It seems to only happen when the car is hot, full operating temp. When it's hot, if I shut the car off and try to start it back up it will barely start because it's pinging so bad. There are 0 codes being thrown.

I replaced the plugs and no change. Old plugs looked alright, a couple were a bit lighter (less brown) than others but nothing too drastic and I removed the fuel pump fuse before I pulled them to run it out of gas so I could do a compression test. Compression test checked out, and I'm not sure how accurate the color of the plugs is considering it probably leaned out just before dying.

I looked at timing advance with a scanner and I was seeing 18-20 degrees at idle and like 40-50 degrees cruising @ ~2000 rpm with light gas, which from what I can tell from googling is normal, though while cruising with light gas and the car hot I can hear the engine pinging. So it seems the computer is commanding the correct amount of advance.

A buddy suggested that the heat could change the resistance in something like a coil pack if it was bad, and cause it to malfunction and also not trigger any codes. I'm really not knowledgeable about how electronics work so I'm not sure if that's valid or not.

Does anybody have any input? I'm really out of ideas short of replacing everything fuel/ignition related until something fixes it, probably starting with coil packs.

 

[Serge]

add a semiyearly problem with my car wild back and was a defective coil pack and dont buy after market there worst after a wild.
i radd after market car was good for 2 summer and started having the same problen when back to stock ford coil pack and car run amazing no noise

 

[DSG2003Mach1]

if what you're hearing really is pinging/detonation its not a spark issue. Youre either getting massive amounts of unmetered air or not getting enough fuel. Im not sure Ive ever heard someone complain of pinging at light throttle.

 

[Roots-type]

I bet it's bad fuel

 

[DSG2003Mach1]

I bet it's bad fuel

thats the only thing I can think of if nothing else has changed. Might be worth dropping the tank and emptying it out (or connect a line to the valve on the pass fuel rail and jump the relay so the pump will stay on with key forward and engine off)

 

[geoffmt]

throw in a bottle of torco octane boost, it costs about $25-30 but will eliminate the fuel as an issue. Bad fuel was my first best guess

 

[anesthetize]

I was thinking bad fuel at first as well, but I put some fresh 93 in (though it was from the same station, but probably a week later and I fill my motorcycle there too which is piped and jetted requires 91 octane+ and no issues). It definitely wasn't coils.

I pulled the new plugs and they were basically completely white. I'm not sure if that could be because I've only run them for about 15 miles and mostly low rpm, otherwise it indicates every cylinder running lean. I would think that eliminates a bad injector (my next guess) unless they all went bad at the same time which seems highly unlikely. I changed my fuel filter just because and no change. Still no codes being thrown.

So I guess I'm going to try looking for vac leaks and cleaning my maf, and anything else I can think of that would cause it to run lean, though I'm getting quite frustrated trying things at random with no codes to go off of..

 

[StrayBullitt]

Yeah I would start by cleaning the MAF. Make sure also that your intake temps and coolant temp are showing to be normal. If you can't restart the car because it's pinging so badly cranking, that actually sounds like an over heating issue, like your combustion chambers/cylinder heads are too hot.