Sirs:
I have a 93 Aerostar 4.0L, auto transmission, factory air, 89Kmiles, always maintaned properly. (I bought this vehicle new in California). The problem is ping when climbing a hill. This problem has developed over time (6 mos) and is slowely getting worse. It does not seem to be temperature or humidity related. I don't drive a lot anymore so it's not a big problem YET! But I would like to solve it before the engine self destructs. Here is what I have done so far: First, I'm aware of the octane requirements as per factory specs. so I do stay at 87 oct. I went up to 89 oct once but no change. I have done the usual - fuel injector cleaners, fuel system cleaner, changed brand of gas, changed air filter, & checked timing. (I didn't know it could change but book says to check it so I did, it's at the factory set point - I think that's 10 degrees BTDC. - no change). Then I changed pvc valve and plugs, and checked the plug wires. Note, all plugs read good, that is, the usual choclate brown color, - no white or detionation. I also changed the MAF sensor, and of course, the fuel filter. I bought one of those digital testers and it didn't tell me anything that I didn't already know, I'm told they don't check down to the specific cylendar on that old a vehicle. I had the fuel pump checked and was told that the volume was a little low. When I pushed for how much I was told 15% - 25%, but I don't have a whole lot of confidence in the mechanic. One other interesting thing is that when I'm climbing a hill, if I floor the gas pedal the ping almost dissappears. Lastly, in the past 2-3 weeks, I am getting some difficulty starting. I'll switch on, hear the fuel pump come to full pressure, then kick it over. The engine will start, cough & sputter once and die. The second time I try the engine stays lit and runs smooth at idle. My guess at this point is fuel pump, fuel pump filter, or dirty injectors (all expensive and difficult for me to work on). I guess it could also be one of the sensors but haven't a clue as to which one. I would sincerely appreciate your opinions and suggestions as I'm on a fixed income and bucks are tight. Thank you.

 

The low fuel "volume" sounds a little strange to me. There are a couple of things you can check. Fuel pump is one, and fuel pressure regulator is the other. If you can get a fuel pressure gauge with the proper fitting, you can connect it to the fuel rail that feeds the injectors to check pressure. On most Ford EFI systems of that vintage, the rail has a Schrader valve with the same threads as the valve stem on your wheels. You can get a gauge from one of the many places that sell parts for Mustangs.

The typical pressure at idle should be about 40 PSI. There is a vacuum hose that connects to the regulator to increase its pressure when the engine is under load. During idle, you can pull that line, and the pressure should increase, sometimes up to 50 PSI. One thing to check when pulling the line is to see if there is any gas in that line. If so, the regulator is leaking, and that could be part fo the problem. If you smell gas in the vicinity of the regulator, it could also be leaking externally. This can cause engine fires if left alone. I've never tried to get to the regulator in my van before, but I can imagine that it will require the removal of a lot of parts, and some major contortions on your part to remove. I think there are 3 cap screws that go in from underneath the rail, so you need a really short allen key to loosen them.

If possible, find a fuel pressure gauge that you can at least temporarily bring into the cockpit, so you can watch it while you drive. If the pressure drops much below 40 PSI while under load, like climbing that hill, you may have a failing pump.

Changing the pump is not all that hard. You first run the fuel to near empty before you start. It helps to jack up the left side of the van, but I don't think it's critical. You need to disconnect the fuel lines, and at least partially drop the tank. The pump is attached to a plate that's fastened to an openning on top of the tank. The pump looks an aweful lot like the one in my Mustang, so I'm thinking one made for a Mustang should work. But you can pull out the old pump in about an hour, and take it to one of those Mustang shops to compare, before resorting to the parts guy at your Ford dealer.

 

Sounds like carbon build-up on the valves. try running a few Bottles of RXP in the fuel. One bottle will treat a tank of gas. Then see if it still pings on you up hill drive. When it starts pinging gets progressive worse carbon is a problem with MTB in the gas now days.

 

It could also be a bad oxygen sensor. I know you are not getting a check engine light but they can degrade long before it will give a fualt code. They should be changed every 50,000 miles. Get a good one made by BOSCH.

 

Many thanks to all who have replied, you have given me excellent advise on what to look for. If anyone else has suggestions please post them. Again, thanks.

 

Hello Muffinman,

What is RXP and where can I buy it? Also what brand of PS in-line-filter should I use?
TIA

 

It's some kind of carbon buster. Most people use it to pass inspection and clean there valves. You can get it at PEP Girls for $5.95 a bottle. I use it once every 3 months.

I used one that the filter could be replaced, They all seem to work ok.

My PS pump as a cooler line that runs out the back of the pump. I followed it down to a hose that had a clamp on it. I removed the clamp and hose and put it there.

 

Also be sure all the vacume lines are tight and not craced.