On Wed, 9 Jan 2008 14:09:55 -0800 (PST), " firstname.lastname@example.org"
Thanks for the reply.
I stopped at my mechanic and explained the situation. He asked me
when this happened. I told him. He said "it was really foggy that
morning". Yes, it was. He told me to go home and try it again. I
did, and it started immediately. I called him back and he said that
the fog was so bad that night and morning he could not keep up with
the phone calls. He recommended changing my plug wires and dist. cap,
and said I could bring it in the next day, or do it myself (he knows I
so smaller repairs myself). I plan to change them when weather and my
Now I got another problem. Maybe someone can comment on this.
Except during that fog problem, the truck runs well. However, every
so often, it randomly goes into a very fast idle. I'm talking 2000 to
3500 RPM. This is most annoying if not dangerous. In fact it became
dangerous the other day when I was hauling a load of hay on a wagon,
and it went into this fast idle when I was on an icy gravel road. I
ended up with a jacknifed wagon, and would have gone in the ditch if
not for quick thinking where I shut off the engine and smacked the
wagon against a large snow pile to stop it.
This happens at random. I called my mechanic again. He said that he
was swamped with work, but if I brought it there, he'd show me
something on the engine. He showed me a Idle (something) device on
the throttle part of the intake. He said it's a solenoid and they
often stick. He suggested removing the two screws and wire, and
either replacing it, or spraying PB Blaster into it, and reinstalling
it. I did the PB Blaster thing, and it seemed ok at first, but its
happening again. That thing does not seem stuck. He told me that
there could be other causes, so I hate replacing parts that may not be
bad. What else could be causing this?
I've worked on a lot of cars, but I am new to Fuel Injection. Please
Note: Tapping on the housing of that thing does not slow the engine
down once it goes into that fast idle. He told me that usually helps.
BTW: If you got here in the middle of this thread, this is a 1990 Ford
F150 4WD pickup, Manual Trans. 302 F.I. engine.
Thanks for all help
The part your mechanic was referring to is the IAC, Idle Air Controller.
Rather than using an idle speed screw on a carb to adjust the minimum
opening of the throttle plate, the IAC allows extra air into the throttle
body to increase the idle speed, and the computer adds extra fuel thru
the injectors to balance the mixture.
If the IAC is stuck open, the engine will race. If you have a vacuum leak
that's greater than the amount of air the IAC normally allows in, the
engine will race (because the computer will close the IAC completely,
and you still have too much air coming in thru the leak).
On a 1990 truck, you're sure to have brittle or cracked vacuum hoses,
including any larger hoses such as to the PCV valve or to the brake
booster. Check them all, and replace as needed. Spray carb cleaner
or direct propane gas around suspected leaks to see if the idle speeds
up. And replace the IAC, it doesn't work forever.
On Tue, 15 Jan 2008 07:58:16 -0800 (PST), " email@example.com"
Thanks for the info. I have not found any bad vacuum hoses, although
it's bery cold right now so I only looked quickly. I apprecaite this
help because like I said, I hate replacing parts that are not bad.
You said to plug BOTH holes. Where are these two holes? I know there
is one under the IAC, which I saw when I removed it and sprayed it
with PB Blaster. If there is 2 holes under there, I guess I didn't
notice (it was cold that day too, so I was in a hurry).
When the engine was racing, I pulled the electrical plug from the IAC
and the engine killed. (if that means anything).
BTW: What would be the easiest way to plug thee holes for the test?
FWIW, most of the problems I've noticed here (and my experience also)
with IAC have been that the engines won't keep running. Time and again,
cleaning the IAC has cured the problem (and saved some $$$). Check
closely for vacuum leaks.
OK guys, figure this out, please.
It's been so damn cold that aside from looking for vacuum leaks (there
were none), I could not work on it. I just had to use other vehicles
most of the time, or deal with this thing racing. Remember, it was
severely cold, at times it hit over MINUS 20 deg. most of the time it
was around zero.
We got a couple warn days when the temp went up to around 40 Above.
That was my chance to work on it. But one problem. When the temp got
to 40, the engine never raced and ran great. Since then, the temp
went back down around zero, hit 15 below one day, but has been on the
zero to 30 Above. Ever since we had those 40 above days, the engine
has not raced since. Something had to be frozen, but what?
This is just a thought. I am likely wrong, but what do you think?
The in-tank fuel pump send the gas to the injectors (and associated
parts). The way I understand it, any excess gas is returned to the
tank. (Is that correct?). Obviously the supply gas lines worked, but
what if the return line iced up? Would that cause excessive gas to
the engine and cause it to race? Obviously any extra gas has to go
somewhere. Does this make any sense? If not, what else could have
Thanks to all.
There temps are in Farenhite (however thats spelled).
On Wed, 16 Jan 2008 09:23:22 -0800 (PST), " firstname.lastname@example.org"
I almost always have a check engine light on, but the reason is
because the oxygen sensor wires are ripped off. I knew about this, my
mechanic said that in order to replace that sensor, I first need to
replace the exhaust crossover pipe. That pipe alone is almost $300.
It includes the Cat-convertor. This is mostly a farm truck, I am not
going to spend a fortune on it, and to replace that exhaust and oxy
sensor, I was quoted nearly $1000 (with labor). That's for a truck
that cost me $600. My mechanic told me that on a truck as old as
mine, running it without that oxy sensor is not really that critical.
He said it would likely get a little better gas milage, but said it
would take a long time to justify spending $1000.
When the weather gets better, I have a friend who has a pipe bender
and saaid he could make me a crossover for under $100. That I will
do, but he said there wont be any holes in it for oxygen sensor.
The truck does run pretty well, except for this racing. It's actually
getting dangerous to drive. Yesterday I was on an icy road and the
engine surged to 3000 rpm. I had to use the brake the whole time to
hold it back.
What gets me is that I can be sitting as a stop light. The engine is
idling at 600 to 700 RPM (normal). I am not touching the gas pedal or
doing anything. Suddenly the engine RPM will increase to somewhere
from 2000 to 3000 RPM for no reason, it may shoot up quickly, or may
just gradully rise. It will also come back down by itself, either
come down partially, or all the way back to the normal idle. In 5
minutes of idling, it may do this several times. It does not get this
fast idle until it's warmed up. When I first start it, it idles
I might have my mechanic put the code tester on it anyhow, if I can
not find an actual leak. I can not drive it this way much longer. I
have been driving my car the last few days and only using the truck
for actual farm work.
But what good will it do when the pipe is patched together and leaks?
That still dont solve the idle problem which is my #1 concern.
Like I said in another post, come warm weather I am going to do what I
can to go back to a simple carburetor engine without all this modern
garbage which does nothing but make the parts stores wealthy by
selling costly parts, and make the dealers wealthy because people cant
repair their own cars. I have a full size station wagon with
carburetor. It's a Chevy, but the engine is the same size (5 liter).
I get better milage with the carburetor. This fuel injection stuff is
garbage. I have been driving cars with carburetors for about 40 years
and they were easy to fix and dependable. Now I got this complicated
pile of junk with enough unneeded parts to melt down and build a
second vehicle, and it's always acting weird in some manner. The last
feul injected vehicle I owned had the in tank fuel pump die, and would
have cost 5 times what I paid for the car to repair. I junked that
If all this complicated emissions junk actually made a significant
increase in gas milage, and really did reduce pollution at the same
time, I might feel differently about it.
By the way, this truck did NOT have this idle problem when I bought
it, this just started a week or two ago. The O2 sensor has been
broken off since I bought the truck, so that is not the cause of the
How difficult is it to change a Fuel Injected engine to a carburetor.
The more I mess with this fuel injected engine, the more I hate it.
Going back to a pre-fuel injection vehicle means getting something
that's pretty old, and thus rusty and falling apart. Yet, I am
finding that fuel injection is going to cost me a fortune for repairs.
The cost of the parts are outrageous. I am a DIY guy, and am finding
myself spending half my paycheck to pay a mechanic, and they dont
always solve the problem until several trys. Rather than going back
to an old rusty vehicle, I'd rather just remove the fuel injection and
install a carburetor from an older Ford engine. How feasible is this?
Otherwise, it looks like my only other option would be to rebuild and
older carbureted engine, and change the whole engine, removing all the
emissions garbage in the process (which is not inspected where I
live). It used to be so easy to work on the old engines. As long as
the engine block itself was working, it meant that either the
carburetor or fuel pump was dead (fuel problem), or it was the coil,
distributor, points (or module), or spark plugs (ingition problem).
These days there is so much garbage it seems the mechanics can not fix
them without numerous trys and spending a fortune.
Not impossible, whether the effort is worth it is up to you, It would
depend on how much you'd need to fabricate.
I'd suggest you see if you can get on some decent tuning software/ scanner
for your motor and get onto some good tuning forums.
A good scanner will tell you a lot about your vehicle's state.
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