This thing pings like crazy on the highway under any load after it warms up. Worse still when the weather is warm. Plus grade used to make it go away, now that isn't even helping.

I've done the basic tuneup. Plugs, wires filters. I have even Seafoamed it twice. I took it to Autozone to read the codes, they have the same cheap code reader as I do for older vehicles. They read a bad EGR.

I suspected that a plugged EGR could cause pinging so I was determined this morning to clean it. I can't even find one on the motor! My manual says it should be on the drivers side of the intake right below the air bypass valve. There's not even a casting in the manifold to accommodate one. This is a 93 4.0 extended van with automatic transmission. Manuf date was 2/93. It has about 95K miles on it.

 

Moving on: I did some Googling on the subject of pinging at speed and found this Q&A. So I searched here again for MAF threads. I can get a rebuilt MAF for $70 but I thought I'd try cleaning it first like some people have suggested. I bought a set of anti-tamper torx at Advance Auto for $10, lifted the sensor and sprayed it down with contact cleaner. I also cleaned the throttle body with carb cleaner, and checked the PCV valve.
I won't know if this fixed anything until it warms up around here. We had one nice weekend and then it got colder again. It sounds like something that ought to be done occasionally anyway. I'll keep you posted.
Never did find that EGR valve.

 

Pardon my rambling but this may be of interest to others. Autozone seems to have a manual online for the Aerostar. It reads just like my Chilton's manual.
This link has a diagram of the 4.0 and where the EGR valve is supposed to be. I hope the link works. Anyway, it looks like a helpful site.

 

Motorcraft Parts does NOT show an EGR valve for '93 4L Aero V6
does show an EGR valve for later 4L V6's

check base timing per Ford Service manual Cd, 10d BTDC at idle
pull codes, are the spark plugs the correct heat range and Autolite or Motorcraft only? any other brand of plug in 4L and one is shooting craps with round dice

do a water injection micro burst steam cleaning of the combustion chambers, works better than Seafoam for removing combustion chamber carbon build up which the 4L is infamous for....with hot engine, 1 qt of water and an 1/8" plastic tube, remove black intake hose at throttle body....one end of tube in water bottle, engine at 2k rpm approx and other end of tube against small hole in throttle body plate....let engine suck in all of the water...should produce an nice cloud of steam out the exhaust....out to freeway for hard run and test....repeat second time for severe carbon buildup

last resort...pull octane plug on firewall wireloom harness...retards base and advanced timing by 4-6d and will lower horsepower
see Ford Service CD and Ford 4L TSB's on Octane plug and preignition aka pinging

winter emissions gas has more ethanol which increases octane and reduces preignition/pinging but has less horsepower production

also run a couple 20oz bottles of Chevron Techron Concentrate or Gumout Regane FI cleaner thru the gas, may be FI's with deposit buildup and poor spray pattern, large fuel beads are worse for pinging, want full atomization of fuel in the air mixture

 

Thanks 96, that solves that mystery!
I'll do the things you suggested incrementally so I can know which one fixes it. It's cold and damp now. As soon as it warms up I can do some road testing.

 

Vango:

Pull the vacuum line on the transmission modulator. You might be sucking tranny fluid in the engine, and that'll will make the engine ping like crazy.

 

Is there a way to set base timing on these engines with EDIS? Maybe moving the CP sensor slightly?

I understand that you can reduce detonation a little by reducing the timing advance, but doing so will also make the engine run hotter; the loss of power goes into more wasted heat. If that gets bad enough, the engine can start detonating again. The correct solution is to clean out the combustion chambers of carbon deposits, and make sure the A/F ratio is correct.

 

Ford did not design any mechanical adjustment to the base timing with EDIS

also, follow copper's suggestion FIRST, the A4LD vacuum modulator neoprene diaphram is infamous for heat breakdown and ATF leakage up the vac. line into engine...that many miles and vac. mod. must be cooked along with ATF
i would replace the vac. mod. no matter what else you find

 

DO NOT LET IT CONTINUE PINGING!!

ken

 

Thanks guys. I don't see any fluid but I'll replace the modulator as a matter of maintenance. It makes sense that sitting next to the catcon it should be toast.
It isn't pinging now because the weather is cold. I will fix it before it gets consistantly warmer. I don't need to damage the engine through neglect.