Ulysses

"John D. Goulden" <jgoulden@okcu.edu> wrote in message
news:dsam510gjl@news2.newsguy.com...
> '91 Eddie Bauer 4x4 4.0L, 220K but with engine rebuild about 10K ago.
> Rebuilder is not my regular mechanic.
>
> This has been driving me (and my mechanic) crazy. Check engine light comes
> on after about 10 minutes; codes are EGO not switching, left bank lean
(hope
> those make sense, going by memory of what they told me here). However,
other
> indicators are that the engine is running rich: poor mileage (12 mpg
instead
> of my usual 16 in mixed driving; black soot in tailpipe).
>
> Computer is relatively new and checks OK. Last time in they replaced the
> thermostat (which wasn't closing and they thought part of the problem was
> that the engine wasn't reaching normal operating temp), oxygen sensor, and
> fuel filter and checked the fuel pressure regulator (symptoms were
> consistent with stuck fp regulator according to Singleton's pages so I had
> them check it - they said it was OK). The thermostat did make a
difference -
> at least the temp gauge comes up pretty quickly now - but mileage didn't
> improve. Catalytic converter is not clogged. Coolant level stays pretty
> constant (fairly new radiator) and no hint of coolant in exhaust.
>
> Any idea on what I / we should look at next?
>
> I almost hate to add this because it's so weird, but shortly after the
> rebuild last summer it was having the same problem (check engine light on,
> poor mileage, black soot / smoke). The rebuilder did a fuel injector
> treatment and the truck ran like a dream - no check engine light and an
> unprecedented 20 mpg mixed (I'm happy to get 16). Took it back in to the
> rebuilder for unrelated things six weeks later and he noticed that a
vacuum
> line was off. He plugged it back in and the problems immediately returned.
> After much head-scratching, his speculation was that the resulting vacuum
> leak was fooling the computer into running extra lean. The line in
question
> was on a connector on the passenger side and runs across the firewall to
the
> topmost connector on the octopus on the driver's side of the engine. If
> anyone wants to take a stab at that one, great. I'm almost ready to unplug
> it again and see what happens, but I'd like the truck to run correctly
> without resorting to such voodoo.
>
> --
> John D. Goulden
> who needs to coax two or three more years out of this truck - then it's a
> new...something, not sure what yet. Some kind of regular bed, regular cab
> pickup, perhaps.
>
>

Hmmm. Did you check for automatic transmission fluid in the vacuum lines,
particularly the one that fell off? This might indicate a bad vacuum
modulator on your transmission. I think, however, that it would take an
awful lot of ATF to do what you described.

Something to check anyway.