4.9 stalls when given throttle
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5th Wheeling
Joined: Sep 2022
Posts: 31
Likes: 4
4.9 stalls when given throttle
Im sure this has been covered but i tried most of the ideas others had and just wanted pointed in the right direction im kinda getting desperate
i have a 94 f-150 2wd with the 4.9 I6 if i give the truck more than 25% throttle it sputters badly and wont accelerate anymore
ive replaced the cap, rotor, ignition coil, fuel pump, FPR, MAP sensor and set the timing because it was originally at 20 degrees BTDC my bud set it to 0 because the ECM set it forward by 10 it ran okay but then i set it to 10 base timing and it ran good without spout but when plugged in it ran terribly however when the engine is warm or hot (because it heats up when idling) it cant stay running at all it rocks the whole truck when it sputters and stalls
havent checked the fuel pressure but im seeing a lot of people saying fuel pressure needs to be relatively high like 45-60 psi what would be the main cause if the fuel pressure is low given i replaced the pump filter and FPR unless I have a faulty pump
what would be a general range to put the base timing so i can use the spout?
i have a 94 f-150 2wd with the 4.9 I6 if i give the truck more than 25% throttle it sputters badly and wont accelerate anymore
ive replaced the cap, rotor, ignition coil, fuel pump, FPR, MAP sensor and set the timing because it was originally at 20 degrees BTDC my bud set it to 0 because the ECM set it forward by 10 it ran okay but then i set it to 10 base timing and it ran good without spout but when plugged in it ran terribly however when the engine is warm or hot (because it heats up when idling) it cant stay running at all it rocks the whole truck when it sputters and stalls
havent checked the fuel pressure but im seeing a lot of people saying fuel pressure needs to be relatively high like 45-60 psi what would be the main cause if the fuel pressure is low given i replaced the pump filter and FPR unless I have a faulty pump
what would be a general range to put the base timing so i can use the spout?
Logistics Pro
Joined: Nov 2013
Posts: 3,928
Likes: 1,198
From: Mojave, Ca
Stalling could be caused by lack.of fuel or lack of electricity. It takes more power to fire the spark plugs when the cylinder pressure is high. So check you could to make sure it has a good connection and to make sure it's operating properly.
Fleet Owner
Joined: Oct 2005
Posts: 20,786
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From: Kentucky
The factory timing setting is 10* BTDC SPOUT out. When you plug the SPOUT back in the computer will advance the timing based on sensor feedback. Not unusual to see the timing bounce at idle RPM. Until you actually measure the fuel pressure throwing anymore parts at the problem will only lighten your wallet.
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5th Wheeling
Joined: Sep 2022
Posts: 31
Likes: 4
its original to the vehicle so 168k on the clock. I have noticed with spout plugged in it drips a bit and back fires when idles or given throttle which made me think is running rich and it only got worse after replacing the regulator
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5th Wheeling
Joined: Sep 2022
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electricity sounds about right when given throttle it kinda goes but then hits a wall and its always at the same point kinda also when at WOT it makes sorta a vacuum sound like a supercharger not sure if thats normal this is my first ford truck
Thread Starter
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5th Wheeling
Joined: Sep 2022
Posts: 31
Likes: 4
The factory timing setting is 10* BTDC SPOUT out. When you plug the SPOUT back in the computer will advance the timing based on sensor feedback. Not unusual to see the timing bounce at idle RPM. Until you actually measure the fuel pressure throwing anymore parts at the problem will only lighten your wallet.
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Fleet Owner
Joined: Oct 2005
Posts: 20,786
Likes: 1,751
From: Kentucky
Is the 55 PSI reading under load or just blipping the throttle? A few ways to test under load: Tape the pressure gauge to the windshield then drive a short distance. Floor the throttle a few times to see if the pressure dips. You can also briefly start the truck, hold down hard on the brake then briefly floor the throttle to simulate a load. Watch the gauge to see if the pressure dips. For a 4.9L engine I would expect a bit more pressure. Perhaps others will chime in as well.
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Lead Driver
Joined: Sep 2002
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From: North Texas
Eyeball that PCV line under the intake plenum. Obviously will not flex under load that I can forsee, but with bits expanding during warm up it could open a crack.
Mine was cracked to hell when I pulled my upper with a few nice splits.
Mine was cracked to hell when I pulled my upper with a few nice splits.
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5th Wheeling
Joined: Sep 2022
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Likes: 4
seems fine but a new issue arises when i gave it throttle to see if the ECM was adjusting timing it started to sputter and buck badly then gave out and wont come back i tested the ignition coil for power and there was no voltage at all no codes nothing at all it just quit. Truck still cranks and it sound healthy its just not firing and i suspect with no voltage to the coil it might just be the pcm failed that easily but i could be wrong. Is there anything that would cause the coil to not have voltage?
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5th Wheeling
Joined: Sep 2022
Posts: 31
Likes: 4
just checked fuse is fine cleaned it off and put it back in swapped it with another 50 amp fuse and no dice btw most of the stuff on this truck is factory if it helps
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5th Wheeling
Joined: Sep 2022
Posts: 31
Likes: 4
there is a solid connection from all the wires back it took me a while but its a solid connection all the way to the ecm all wires are fine and are in usable condition not the best but it shouldnt cause an issue ill order another ECM and crack this one open and report my findings tomorrow from what ive researched when these things fail its pretty obvious
Fleet Owner
Joined: Oct 2005
Posts: 20,786
Likes: 1,751
From: Kentucky
I do not follow your logic here. Why would you replace a computer (ECM/PCM) because there is no power to the coil?
With the key in the Run or Start position power will be applied to the coil. That has nothing to do with the computer. Based on your problem statement: i tested the ignition coil for power and there was no voltage at all you have a basic power issue, not a bad computer at this point.
With the key in the Run or Start position power will be applied to the coil. That has nothing to do with the computer. Based on your problem statement: i tested the ignition coil for power and there was no voltage at all you have a basic power issue, not a bad computer at this point.