My '92 3.0 Aerostar was pinging for several years. Had to run midgrade fuel or higher. Tried water through intake on hot engine, tried fuel system cleaners, tried thicker oil (thinking less oil consumption may help as it uses 1qt/1300 miles), tried Italian Tuneup. Nothing worked. So I had the timing retarded 4 degrees. Hasn't pinged since. A bit more sluggish though.

 

there is an Octane plug in the wiring harness on fire wall of 4Ls only that retards timing approx 4 degrees for pinging issues, Ford TSB

 

Hey 96,

My firewall is a little busy. Can you describe where that plug is, and what it looks like?

thanks

 

Top LH rear of engine compartment, taped to engine control sensor harness (A8)

2 wire plug/socket dk green from pin 44 of PCM and GY/R TO pin 46 data sensor common PCM

from memory, black plug...only pulled for testing...never had to leave one out to solve pre ign. prob.
noticible drop in power and gas mileage especially with load

 

According to Chilton's, on a 1990-91, it's an orange wire from pin 44 of EEC, and the other side is black/white. I found the plug taped to the bundle of wires coming from the EEC connector. The common wire looks like black stripe on white, instead of black with white. The plug is gray. I think this is it. So is the timing retarded with the plug removed or in place?

 

retarded when removed

 

I would look at retardation (no offense anyone) as a last resort. Did you try the other suggestions here first?

Late timing results in performance and mileage degradation.

 

First try a tank of shell or Esso fuel, if this does not improve the pinking,......

Gentlemen, as we all know, the most likely cause is carbon build up somewhere in the combustion chambers. That carbon is glowing red hot on acceleration, it needs to come out ! More importantly is there a condition in the engine which caused this premature build up of carbon (assuming this to be the cause).
An unburned fuel condition or misfire could do it, as can multiple cold short trips in a cold engined vehicle.
Did I not read that Aero's can do this (not to excess) & not be cause for alarm as long as no pre-ignition (detonation ) occurs?!?

Go for it ......................first nice warm week-end rip off the heads & de-carbonise the engine!!!!

All the best, Aeroman.

 

Ford put out a TSB on 4L pinging preignition combustion chamber carbon buildup problems and an expensive version of Berryman's B12 or Seafoam

caused by head combustion chamber design with thin casting and cool spots allowing carbon to buildup

 

Well, on my 91, that runs like a hotrod compared to my 90, it is pinging more under load. I have run Seafoam, Techron, isopropyl alcohol, injector cleaners, and water through the intake manifold as well as the gas tank (no water), but it did not help. In fact, I'm thinking that it's now pinging more than before. Otherwise, it starts easily, runs very smoothly, and does not burn oil. I don't see any ATF in the vacuum modulator, and the running temperature stays right around the middle of the scale. I cleaned out the MAF sensor, and replaced the HEGO sensor; no change. I think that covers all the basic checks and simple fixes.

I don't know the care provided by the previous owner, but I am assuming the worst. When I had it smog checked, it barely passed the HC test.

I will next pull some plugs to see how they look. Other possibility may be that the fuel pump is dying, and not supplying enough pressure under load. But that's harder to check when my fuel pressure gauge needs to sit right on the Schrader valve. I'm thinking of modifying an oil pressure sender and gauge to monitor the fuel pressure.

As a last resort, I will pull the octane adjust plug. As others have reported, backing off the timing will maje the engine sluggish. This loss of efficiency will translate to more heat lost, which will make the engine run hotter, which by itself can cause overheating. But I'm running out of options.

 

xlt,
if it's not a bad hot plug then look for a vacuum leak
4L's are notorious for vacuum leaks....the intake manifold-plenum bolts shake loose....the vacuum lines on a 4L are a nightmare, too many and too short...easily blown off, cracked or pulled off
the tubes on the vapor canister die from gas vapors. i replaced mine a couple years ago, they were cracked and split
the vac. lines on your 91 are 16 years old

high emission HC indicates a rich mix?

does your "pinging" quit with 91 octane or pulling the octane plug?

 

He's right, high HCs with the other gases relatively nomal mean you are running rich. I need to go through my 4.0 and look for signs of loosened bolts and vacuum lines. However, mine has not yet had any pinging. We just fixed my truck which was starting to ping badly. One of the injectors was plugged, causeing the one cylinder to run lean. It caused the other cylinders to run way rich. I pulled a fuel rail and 4 injectors from a junkyard car. However, this is much easier to do in a 4 cylinder pickup than an Aerostar. I would want to be sure that a bad injector was to blame before trying to replace them.

 

my 94 3.0 pings also. been through all the recomendations listed previously and still get what i assume is pinging(barely audible,only after fully warmed up and driven about 10 miles).
could this possibly be a faulty coil?(coil on distributor)before changing my plugs and wires,i pulled the doghouse off and drove around the block at night. it was a fireworks show from the old cracked wires.
could this trash at least partially trash a coil?

 

It is possible, however, coil packs are expensive so I would try to stay clear of that idea as long as possible. Another thing that can cause a sound that could be confused with pinging is lifter noises. The pushrods or lifters get work and can sound much like knocking. Try a better oil or use a product like AutoRX and see if that doesn't help.

 

Light pinging like that, wont harm your engine. Also the leaky wires wont harm your coil(s). Coils dont care where the spark jumps to, but your engine will !! Also a faulty coil would likely cause misfire or difficult starting; not pinging.

Pinging is caused by locally overheating engine due to high combustion temp or carbon build up which can increase compression ratio or actually burn in the engine. Use of a too low octane fuel (Not likely in an A/star). Lean mixture & cooling system problems could make the situation worse. Increased compression or advanced combustion could cause pre-ignition or detonation (like how a diesal engine works) which is a much heavier knocking noise & can wreck engines not designed to run this way!!nAnother clue is if your engine runs on when you switch off the ignition.

If you can get rid of the problem by using higher octane fuel,then it is likely that the carbon build up is causing increased compression ratio or is thin enough in an area to glow red hot (sometimes on a fouled plug),which can cause the pinging.

ATB Aeroman.