5.0 hesitation

Clark · 06-29-2010, 10:08 PM

Friend has a factory fuel injected 5.0 in his Ford F150. Of late, the 5.0 is getting noticeably poor mileage and a bad hesitation when opening the throttle. The computer shows no error codes.

I'm not a computer/fuel injection guy, but anything we should look for? Vacuum leaks? Intake manifold leaks? Bad injectors? Water in the gas?

Hillbilly · 06-29-2010, 10:50 PM

Vacume leaks first Clark. The hard plastic lines to the fuel pressure regulator and smog pump, egr valve controls could have a mouse bite hidden underneath where you can't see them. Same problem with the rubber lines connecting the charcoal canister and solenoid to the intake vacume. If you get black fingers from touching those hoses, replace them. You didn't say what year 150 so I asume it is new enough to have a mass-air sensor at the air filter housing. The big rubber double intake air pipes from the mass-air sender to the throttle plates can get brittle and crack from rough treatment while replacing the air filter element. A crack in those hoses will mimic your symptoms. Gotta' have a good strong signal from the mass-air or it won't run worth beans. Hello Woody Anderson ! Not a cheap fix but not super expensive.

HuevosRanchero · 06-30-2010, 08:48 AM

my understanding is the pcv screen filter on these motors gets forgotton about a lot of times and can be terribly clogged....might be worth checking?

5.0 Chero · 06-30-2010, 08:58 AM

Quote:

Originally Posted by HuevosRanchero

my understanding is the egr screen filter on these motors gets forgotton about a lot of times and can be terribly clogged....might be worth checking?

Did you mean PCV filter screen?

Dirty Mass Air Sensor. Plugged fuel filter are possible causes

HuevosRanchero · 06-30-2010, 09:01 AM

Quote:

Originally Posted by 5.0 Chero

Did you mean PCV filter screen?

Dirty Mass Air Sensor. Plugged fuel filter are possible causes

YES! ugh...sorry..didnt sleep much last night!

Denny · 06-30-2010, 10:02 AM

Quote:

Originally Posted by 5.0 Chero

Dirty Mass Air Sensor.

The mass air sensor could make it run bad, but wouldn't it show an error code?

5.0 Chero · 06-30-2010, 10:08 AM

Quote:

Originally Posted by Denny

The mass air sensor could make it run bad, but wouldn't it show an error code?

not all the time

burninbush · 06-30-2010, 01:31 PM

I wonder if it would be worth having the injectors tested? One or two running very rich might trick the computer into setting the rest lean.

The next thing that comes to mind is it might all be due to a throttle-position sensor getting noisy. And air and water temp sensors could be failing.

What year pickup?

Clark · 07-06-2010, 09:33 PM

Finally looked at this truck, a 1990 Ford F150 with a fuel injected 300 cid six. Obviously it helps to look. I also wonder if this is the first year they injected that engine. It still has an air pump with all the plumbing and the throttle valve mounted to the intake manifold. Since there is no remote mass air sensor, I wonder if this is a speed/density system?

The engine does hesitate when the throttle opens but the engine runs smoothly once it catches. With all that plumbing, I'd hate to guess the source of the problem.

Hillbilly · 07-06-2010, 10:10 PM

Speed density type. Those were prone to need a new MAP sensor ( manifold absolute pressure ) a few years ago already. Located on the passenger side fender with a direct to the intake vacume line. Could be a lazy gummed up air by-pass valve and motor too. Know anyone that has a code reader you could borrow and plug it into temporarily ? Should be reading codes out of parameters somewhere even without the check light.

06-29-2010, 10:08 PM	#1
Clark Senior Member Join Date: May 2003 Location: Huntsville, Alabama Posts: 1,184	5.0 hesitation Friend has a factory fuel injected 5.0 in his Ford F150. Of late, the 5.0 is getting noticeably poor mileage and a bad hesitation when opening the throttle. The computer shows no error codes. I'm not a computer/fuel injection guy, but anything we should look for? Vacuum leaks? Intake manifold leaks? Bad injectors? Water in the gas? __________________ '75 GT, original 460/C6, 252,000 miles.

06-29-2010, 10:50 PM	#2
Hillbilly Senior Member Join Date: Jan 2008 Location: Winchester, TN. Posts: 1,775	Vacume leaks first Clark. The hard plastic lines to the fuel pressure regulator and smog pump, egr valve controls could have a mouse bite hidden underneath where you can't see them. Same problem with the rubber lines connecting the charcoal canister and solenoid to the intake vacume. If you get black fingers from touching those hoses, replace them. You didn't say what year 150 so I asume it is new enough to have a mass-air sensor at the air filter housing. The big rubber double intake air pipes from the mass-air sender to the throttle plates can get brittle and crack from rough treatment while replacing the air filter element. A crack in those hoses will mimic your symptoms. Gotta' have a good strong signal from the mass-air or it won't run worth beans. Hello Woody Anderson ! Not a cheap fix but not super expensive. Last edited by Hillbilly : 06-29-2010 at 10:53 PM. Reason: Brain fart - -

06-30-2010, 08:48 AM	#3
HuevosRanchero Senior Member Join Date: Jan 2008 Location: Middle Ga Posts: 2,958	my understanding is the pcv screen filter on these motors gets forgotton about a lot of times and can be terribly clogged....might be worth checking? __________________ '76 Ranchero GT 460 C6 184,000 "Rocky" '80 Cobra Mustang V8 255 Auto 132,000 "Cookie" '97 Taurus Work Wheels VII V6 3.0 264,000 "Torrie" '08 Mariner Family Barge IV V6 3.0 052,000 "Marnie" '96 Mustang V6 3.8 Auto 057,000 "Pony" Last edited by HuevosRanchero : 06-30-2010 at 09:01 AM.

07-06-2010, 09:33 PM	#9
Clark Senior Member Join Date: May 2003 Location: Huntsville, Alabama Posts: 1,184	Finally looked at this truck, a 1990 Ford F150 with a fuel injected 300 cid six. Obviously it helps to look. I also wonder if this is the first year they injected that engine. It still has an air pump with all the plumbing and the throttle valve mounted to the intake manifold. Since there is no remote mass air sensor, I wonder if this is a speed/density system? The engine does hesitate when the throttle opens but the engine runs smoothly once it catches. With all that plumbing, I'd hate to guess the source of the problem. __________________ '75 GT, original 460/C6, 252,000 miles.

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06-30-2010, 01:31 PM	#8
burninbush Senior Member Join Date: Mar 2006 Location: near SF Posts: 4,648	I wonder if it would be worth having the injectors tested? One or two running very rich might trick the computer into setting the rest lean. The next thing that comes to mind is it might all be due to a throttle-position sensor getting noisy. And air and water temp sensors could be failing. What year pickup?

07-06-2010, 10:10 PM	#10
Hillbilly Senior Member Join Date: Jan 2008 Location: Winchester, TN. Posts: 1,775	Speed density type. Those were prone to need a new MAP sensor ( manifold absolute pressure ) a few years ago already. Located on the passenger side fender with a direct to the intake vacume line. Could be a lazy gummed up air by-pass valve and motor too. Know anyone that has a code reader you could borrow and plug it into temporarily ? Should be reading codes out of parameters somewhere even without the check light.