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post #1 of 2 (permalink) Old 06-25-09, 08:37 AM Thread Starter
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mad Getting 6.4 MPG 95 3.8L Windstar all new parts

This thread scares me:
95 windstar 3.8 engine/fuel issues

Sorry to type so much, but I have been trying to fix this relentlessly every month for over 2 years now. I am determined it can be fixed, but I am really losing hope. I'm hoping there are some real well experienced people on here that can help me. If you can think of it, 90% (including transmission, engine, and the usual stuff) of the parts on this vehicle have been replaced. The entire fuel system has been rebuilt (every fuel component) with the exception of the lines themselves.

Only things I can think of that hasn't been replaced is the EVAP stuff, Ignition Control Module, Crankshaft Position Sensor, TPS, O2 Sensors (OBDII and no codes), ECT (tested), IAT, MAS (used, but ok and cleaned).

A melted wiring harness was repaired thinking this would resolve the issue completely, but then it was discovered that the injectors were being held open all the time by a faulty PCM. New PCM installed, 40 miles down the road and 1/4 tank of gas burned/lost later I'm getting basically 6.4 mpg at that rate.

I've been told to DRIVE IT FOR A COUPLE WEEKS and SEE..... as I have been told before, but thats a bunch of bs. Computer relearning will not deduct more than half the MPG I should be seeing.

It seems like every time I make a fix or improvement to the engine bay that the MPG gets worse. It honestly seems this way. I've systematically gone through every ground point and sanded it and rebolted it tight and made sure its good to go. I've resistance tested everything. There are 3 ground points 2 in front of the radiator on the body metal and 1 under the battery that I haven't undone, but they ohm out fine to me.

Since the computer was replaced I seem to have a slight long starting problem ONLY WHEN WARM (never when COLD, COLD starts right up), the engine idle ALWAYS dips TWICE after the radiator fans CUT OFF, and the MPG issue are the only symptoms I have to go on.

Disconnecting the battery and ohming the injector wires show that the short to ground that was holding the injectors open is gone, but I have not checked DC operating voltage a Key On Engine Off, or Engine On.... but I have to be losing gas somehow/somewhere.

Fuel pressure spec is 28 - 45psi. On my van it never goes above 28 psi and drops to 26psi when you rev it even the slightest. Fuel pump is new, as is filter, regulator & injectors.

Only other thing I can think of is the performance coils I have in there, but thats the only thing non-stock I have in there.

What does it mean when every fix/repair/improvement made makes the MPG worse? Is that a general rule of thumb that it means its always electrical?

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post #2 of 2 (permalink) Old 06-25-09, 07:09 PM
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Re: Getting 6.4 MPG 95 3.8L Windstar all new parts

Electrical gremlins are the worst kind. I'd replace the O2 sensors, as you mentioned you haven't done that. Even if the engine light doesn't come on indicating an O2 sensor fault, it can take a LONG time for the computer to see the fault. As you replaced the computer, the new unit might think that the current O2 sensors are functioning correctly. The O2 sensors monitor the exhaust gas along with the MAF sensor (you MAY not have one, located on the air intake tube before the TB). The O2 sensors help keep the air/fuel ratio at the proper 14.7:1 for most efficient operation. It would seem if you've replaced all those components you mentioned, and still get poor mileage then I'm sure the computer is giving the engine more fuel than it requires to operate.

If anything else, I'd start there and hopefully the PCM will learn the O2 sensors after a few miles and you'll see an improvement at the pump. Also, make sure the engine timing is correct and the spark plugs have been gaped correctly.

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