97 GT pings badly

[bhuff30]

Hey everyone. I am normally in the 2.3 forum, but I have a question for the 4.6 experts here.
My dad has a 97 GT and it has a problem with pinging. It pings pretty badly at full throttle or even 3/4 throttle. He tried running premium, and it still pings when you get on it. It is bone stock and has about 90K miles on it. It certainly shouldn't ping that badly with only 9:1 compression. The CEL isn't on, and he has tried running a bottle of injector cleaner through with no success. It has gotten worse recently because they switched to the winter gas, and the temps are still warm at times.
My best guess would be a lack of fuel. Maybe the fuel filter, or a bad injector. What is the most common cause of high load detonation on a stock 4.6?

 

[NiteRydaGT]

If you suspect it's not getting fuel I would look at the fuel pump. Mine was taking a crap at 68,000 miles. If your going to change that out might as well do the fuel filter at the same time. I was having lack of fuel issues. A 255 LPH fuel pump, new fuel filter, and a adjustable fuel pressure regulator solved it.

 

[CanadaStang]

Possible causes:
1) Fuel pump/filter as SR 97 GT suggests. If you know someone who works in a garage, hook up a fuel pressure gauge and check the pressure. Should be 30-40psi
2) Intake leak. Check for cracks in all the hoses going into the intake and/or check manifold vacuum[gauge should hold a steady 17-22 in.Hg]
3) Dirty MAF sensor. Clean MAF sensor wires
4) Blocked EGR [if you have questions on how to check, PM me and I'll explain]
5) Carbon build up in combustion chambers. Use a combustion chamber cleaner.[check the additive section in your local automotive store.
Check the easy stuff first. Hope this helps.

 

[Stanglover96]

My 96 did that and my uncle said it was spark knock, so I changed the plugs and it was all fine.

 

[tontot77]

sell it

 

[bhuff30]

MAF: I thought the biggest cause of dirty MAF's was oil residue from performance air filters? If that is the major reason, then it should be fine since we still run paper filters.
I think the
next step will be to replace the fuel filter. I am not sure if he has replaced the plugs recently, but if an injector is bad, it will probably show up on the corresponding spark plug.
The plastic intake was replaced by ford once several years ago. It did the standard split at the water passage. If the problem still exists, we will start looking for vacume leaks and check the fuel pressure and vacume at idle.

sell it

Good plan. Actaully, after they get the bugs worked out of the 05, I think he will buy an 06 GT mustang or whatever the mid model ends up being (mach 1, boss, ect), but that is still several years in the future.

 

[98stangv8]

I have heard of several people (including me) that had problems with fuel pumps..you may want to check that.

 

[2002BLGT]

if the plugs are OLD and I mean really old , its possible for the electrode to have been burned away making the gap too large which is causing a larger spark in the combustion chamber ..... just an idea , Fuel filter or pump is another probable cause ....