Hi guys,
My new-to-me 1990 F150, 54-speed, 5.0 L, fuel injected V8 stalls whenever I slow to make a turn. This is dangerous because I lose the power assist for the brakes and steering.
I have tried spraying the vacuum lines with carb cleaner, but didn't detect a change in the sound of the running engine.
I have removed the idle by-pass, cleaned it and sprayed it with WD-40, and reinstalled it. No detectable change.
The engine seems to run fine except for this stalling. Any ideas about what I should check next?
Thanks,
Randy Olson
Ithaca, NY

 

i would check to make sure the IAC is working right.

correct me if im wrong but when the truck's idling, you unhook the IAC (on the throttle body) and if the idle doesnt change. you need a new one, or at least it needs to be cleaned

 

Hi,
I checked the IAC valve by disconnecting the wiring to it at the throttle body. The engine immediately stopped. I reconnected the wiring and restarted the engine and it ran normally.
Randy
1990 F150 5.0L

 

I believe that this is normal for a correctly functioning IAC.

Is the ldle low before the engine dies? Do you have a tach?? If so-what is it showing right before the engine dies? Can you keep the engine alive by depressing the throttle right when it is acting like it is going to die? Is this trouble more likely to occur when there is a high electric load on the alternator? You do have a manual transmission-right??

 

The engine idle is not low before it stops. It is probably around 600 rpm. I cannot keep the engine going by depressing the throttle...at least I haven't tried to, so maybe it's possible.
It occurs when there is no electric load on the alternator other than normal operating equipment. In other words, no radio, lights, or other equipment is turned on.
And, yes this is a manual 5 speed tranny.
Randy

Is the ldle low before the engine dies? Do you have a tach?? If so-what is it showing right before the engine dies? Can you keep the engine alive by depressing the throttle right when it is acting like it is going to die? Is this trouble more likely to occur when there is a high electric load on the alternator? You do have a manual transmission-right??

 

Randy:

I just remembered that only on the 5.0 with manual transmission-there is a sensor on the high pressure power steering hose that tells the computer that the steering is turning and causes the idle to increase during the turn. This sensor is there to prevent stalling during a turn!!


It looks like a high pressure sensor on an AC hose. And has wiring going to it. Look to the left of your steering box and you will see it staring back at you!


If you have a scanner-you can do a test and verify that this sensor is bad or the wiring to it is bad.

I bet that this sensor is the source of your trouble-if the truck only dies during a turn.

 

I'll look for the sensor on the steering, but I'll bet anything I won't find it because this truck originally came with an automatic tranny. The previous owner converted it to a manual.
Randy

 

Where is the steering box noted below located?
Randy

It looks like a high pressure sensor on an AC hose. And has wiring going to it. Look to the left of your steering box and you will see it staring back at you!

 

Seriously? I might have to look into this myself, as my truck has a habit of stalling out as I'm making a sharp turn. It also putters a bit under hard acceleration, and doesn't seem to be as bad when I've got more than half a tank of fuel(though it still happens sometimes) so my first theory was something floating around in my gas tank, though.

 

Yeah-I always wondered why it would be necessary for a V8 to have to idle up when the power steering is turned at low RPM.

I would definitely look into this sensor on the high pressure hose if you have a 5.0 manual that stalls when turning.

"Putters under hard acceleration". When was the fuel filter last changed?? Have you checked the fuel pressure regulator for gas on the vacuum side?

 

To the left of the coolant overflow and windshield washer tanks. Find the steering column and follow it to the frame. You will see the steering box with two hoses connected to it. The hose with the sensor wired to it will be the sensor that I am referring to .

 

I changed the fuel filter in the fall, but until recently, this truck had the filler cap in the bed of the flatbed, which is where my "junk floating in the tank" theory came from. The way I monkeyed the couplings though, the next fuel filter change might also be a fuel line change...

 

I think I'm getting somewhere with this stalling-when-turning issue. At least I may have a smoking gun.
The power steering pressure sensor is located where it should be on the fluid line attached to the steering box. The wires running from the sensor go into a bundle of wiring. It appears that the same wires come out of the bundle and terminate in a connector. This connector is not connected to anything; it is just dangling near the throttle body. While the connector looks like the one that goes to the Idle Bypass Valve, it could go to something else. The question is "Where should this wiring be connected?"
The Haynes manual states that work on the power steering sensor and wiring should be done be a real mechanic, not a DIY person like me. Any thoughts on that?
Randy Olson
1990 F150, 302, 5-speed

 

My Haynes manual shows that the yellow/green wire goes to the ECM/computer,pin number 24 and that the other wire-grey/red goes to what looks like a common ground for the PS pressure sensor and other sensors .

It is late at night and I will open the hood tomorrow and check and see what I can see on my 5.0 manual's P/S sensor. I will try to see where the physical connectors are and what it is connected to in the engine bay.

 

That would be great if you could tell me where the wiring goes physically in the engine bay.
Thanks for all the help!
Randy