Many people leave the engine running when they wash it. The
5.0 & 5.8 engines used a two piece intake manifold. Many of
them experienced failure of the gasket between the upper and
lower sections of the intake. If the engine was running
when he wet it, it probably sucked some water thru the bad
place in the gasket making it seal a bit better momentarily
changing the the way the engine was idling. Replacing the
gasket usually fixes that problem. I thought we had
mentioned that as part of the check for vacuum leaks earlier
in your problem - maybe it was another thread. You can
check this gasket for bad leaks with a can of carburetor
cleaner or even WD40. Don't use starting fluid (ether) for
this. If that is the problem, it is a cheap straight
forward repair to remove the upper intake, clean the gasket
surface and replace the gasket using a very thin coat of
sensor safe silicone sealer like the Permatex Black or Gray.
You should be able to do this job in under an hour even with
OJT. Allow it to set up for about 10 minutes before
installing the upper intake. Also, if you do this, make
sure you do not pinch the small plastic vacuum tubes that
pass by the back of the manifold. That is very easy to do.
IIRC, the 5.8L also has a torx head bolt in the middle like
the 5.0L. I don't recall the size but, you will need to use
a long 1/4" drive extension to reach it from the top. It is
much less frustrating if you use electrical tape and firmly
attach the bit and socket to the extension unless you have
very small hands to fish it from under the manifold. If you
get an upper intake gasket kit, it will have a throttle body
gasket so you can disconnect it and push it forward out of
the way. You don't have t worry about losing any coolant
from the intake as it is dry. You must use a good accurate
torque wrench to install the bolts or you will cause a
bigger problem than you are fixing. You may be able to
borrow one that will work accurately in the 250"/lb range.
I do not recall the exact setting for those bolts. You will
need metric tools and a way to adapt your sockets for the
torque wrench to 1/4" drive unless you come up with a good
1/4" drive torque wrench.
I hope I have written this such that it is understandable.
It has been a long time since I was intimate with this exact
engine. I believe Tom who has responded above is still an
everyday Ford tech with about a hundred years experience.
His answers are usually dead on on the Fords given enough
Thanks Lugnut. You did mention the manifold gasket, but I didn't use
your test because I'm leary of spraying carb cleaner at a running
motor. Since the problem only occurs for about 65 seconds, I'd have
to crank the motor, run around to the motor and start spraying at the
joint between the lower manifold and the long curved stacks that
follow the throttle body. Is that right, and what am I looking for?
rpm change? It looks like I'd only be able to get to the left side.
Why wouldn't spraying carb cleaner on a hot motor start a fire?
Anyway, the ford tech (the one that wants $315 minmum to hook up the
breaker box) said he didn't think it was a gasket problem. And the
other guy (at the foreign car shop) told me it probably isn't the
EEC. Seems like that leaves sensors. But, what do I know? Not that
I believe you are looking at the right one. You do not have
to use the cleaner or whatever while the engine is acting up
as long as it has stabilized. When the idle goes down, it
simply means the ECM has compensated for it's inputs. If
the gasket is bad, the idle will change when the spray hits
the leaking area whether it is idle quality or speed. You
will recognized the change it it is significant. You are
very correct to be concerned about spraying flamables on a
running engine. The pros do it routinely but, they also use
WD40 quite often which is much less combustible and safer.
Unless you have electrical sparks, the engine will not be
hot enough to ignite carb cleaner or wd40. Ether is a
The Ford tech may be correct about the gasket but, a
problem like yours may at some point require the tech to
make this test as part of the overall diagnosis. A good
diagnosis is going to start with a thorough visual
inspection to make sure everything is present and correctly
connected. The next step will be a check for fault codes
and the KOER diagnostics which will hopefully tell the tech
at least which system he needs to investigate more closely.
At this point, the tech should begin to do certain
procedures that will pinpoint the problem. A good tech who
can find your problem will be much less expensive in the
long run than just throwing parts at something or spending a
lot of time on something you do not and will not understand
without first having a good fundemental knowledge of the
You are correct in being cautious but, you apparently
already have a great deal of time and grief related to this
problem. It may be time to place your faith in someone
local who can personally examine the vehicle. Contrary to
what you may feel after reading some of the stories about
service organizations, most of them are people just like
yourself who do not wake up in the morning looking for their
next scam victim. They just want to make a living and most
techs would much rather have a repeat customer than a one
timer. If you go to a well qualified shop or dealer, they
will be glad to show you their training and qualifications
before beginning work. If they are certified ASE or Ford
techs in emissions and driveability, they will have the
No, no. I do not think they are all scammers. I think the Ford tech
and the foreign tech were straight shooters. They just could not find
the problem. The next step is apparrently very very expensive. I
can't see spending $1000 bucks on this. I already have an offer on
the truck. I just might sell it at this point. Damn shame, after all
the maintaince and care I've put into it, but it is what it is.
I'm going to squirt some WD40 at the seam (fire extinguisher at the
ready). And I may change out the TPS too.
When I washed the engine off to degrease it the water sealed around
the gasket. Once it started to dry the speed went back up. So I
replaced the gasket and they engine ran perfectly. No more high idle.
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