I have a problem that has me a bit perplexed...
Today a friend of mine and I started up two 5.0 cars that sat in a field for
the last few months or so, waiting for the spring thaw. Both cars are as
stock as you can find 'em, and ran with no problems when parked. The one,
an '85 GT 5.0 CFI AOD fired right up after a battery charge. Not a problem.
The other, an '88 LX 5.0 SEFI 5-speed, didn't want to run. At all, not
cold, not warm, nothing. It didn't need a charge, but immediately upon
start up, it sputtered and died. It won't hold an idle. It doesn't seem to
rev up at all when hitting the throttle, but pumping it was ok and it would
get to almost 2500RPM with a quick 10%-0 repeated pumping cycle. Hitting
the throttle to the floor made it just slow to a sure stop every time, like
it only wanted to rev when the throttle plate was closing or closed.
Backfires or afterfires (not sure if it was burning up in the cats or in the
intake) were common during this pumping, especially when going more like
75%-0 continuously.
Grabbed some tools and took a look. I didn't have my computer scanning
tools, and the '88 didn't have a CEL, so I don't know if it was throwing a
code. That's for the next adventure.
First, added some dry gas mixed with a fresh couple gallons of 93 octane.
Both cars sat the same length of time, but maybe one had questionable gas.
This did nothing.
Checked all the wires... they're fine and connected. Pulled the cap, and it
was a little corroded, so we cleaned it up a bit. Still no change.
Pulled the IAC plug, and it actually held a 500RPM idle. I was shocked. By
my deductions, it was getting too much air for the fuel it was getting.
Putting a fuel pressure gauge on the schrader valve showed 30PSI at this
idle, and the number would fluctuate with the throttle, but not drop below
30.
I put a timing light on the coil wire at 500RPM, just to see. There was a
miss every now and then, showed by the light and the stutter of the engine,
but it was fairly constant. Pumping the throttle to rev it up, there were
no breaks. Same with using plug wire #1. Even with the full-throttle from
2500RPM, the light never missed, but the engine was slowing fast.
Timing at 500RPM without the SPOUT (yes, it ran that way too as long as the
IAC was disconnected) was around 14 or 15 degrees, running 93 octane gas.
My theories at this point (without a computer scan) are...
O2 sensors wouldn't matter because it did this cold, well before the sensors
would be used for fuel trim anyway
MAF sensor is N/A - this is a speed density car. The only other tools used
to map the fuel are the RPM, TPS, and MAP. The hall effect sensor in the
distributor could be bad, the TPS could be way off, the MAP could have
problems, could be a vacuum leak (though none was heard), or injectors could
be plugged.
The car hasn't been tuned in a while, so my friend will throw a cap, rotor,
plugs, and wires on it... but I have a feeling it won't help. The light
shouldn't light unless the plug fires or is shorted together somehow, and
the 500 RPM idle was mostly smooth, indicating a fire on all 8.
Any other suggestions or things that I'm missing? We have a spare
distributor out of a known-good engine, new 19# injectors in a Ford box, and
MAP sensors are pretty cheap. I just hate throwing parts at a problem, even
if the parts are free.
TIA,
JS
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