Fighting the dreaded “stumble under load” issue
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1st Gear
Joined: Nov 2024
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Fighting the dreaded “stumble under load” issue
Hello
I have been fighting this issue for a while now (due to financial issues). I have a 2005 4.6l 2wd Screw. The problem has been that after the truck gets warmed up, it cuts out when I accelerate and when I let off the pedal it comes back. The MIL comes on and the codes are P0171 and P0174.
So far I have changed the intake, spark plugs, fuel rail pressure sensor, maf sensor and the fpdm. I am going to change the pcv valve, injectors, fuel filter and fuel pump.
Wish me luck and I will update in about a week.
I have been fighting this issue for a while now (due to financial issues). I have a 2005 4.6l 2wd Screw. The problem has been that after the truck gets warmed up, it cuts out when I accelerate and when I let off the pedal it comes back. The MIL comes on and the codes are P0171 and P0174.
So far I have changed the intake, spark plugs, fuel rail pressure sensor, maf sensor and the fpdm. I am going to change the pcv valve, injectors, fuel filter and fuel pump.
Wish me luck and I will update in about a week.
Fleet Mechanic
Joined: Jul 2019
Posts: 1,316
Likes: 312
Let’s lay off firing the Random Parts Cannon so much. Most of what you changed has nothing to do with running lean on two banks.
Definitely check for brittles hoses. I think the brake booster has one that runs to the intake. I don’t know if it disappeared for this generation truck, but the 10th Gens had a hose that run from the back of the intake facing the firewall and ran to the passenger side valve cover. It liked to rip and collapse on the back.
Fuel pump? Maybe. But, check pressures first. Save some money. A shop visit from that start would have been cheaper if you are having money issues, as odd as that sounds.
Definitely check for brittles hoses. I think the brake booster has one that runs to the intake. I don’t know if it disappeared for this generation truck, but the 10th Gens had a hose that run from the back of the intake facing the firewall and ran to the passenger side valve cover. It liked to rip and collapse on the back.
Fuel pump? Maybe. But, check pressures first. Save some money. A shop visit from that start would have been cheaper if you are having money issues, as odd as that sounds.
Fleet Mechanic
Joined: Dec 2003
Posts: 1,436
Likes: 117
From: Virginia
Questions:
Do you have a scan tool?
If yes, one that can read live data?
Have you looked at the readings on your O2s switching?
Have you looked at the operating temps of you converters?
Have you checked the misfire counters on each cylinder?
I would agree with Johnny about the random parts.
Some of those things are regular maintenance items like fuel filter & plugs, etc... so yea, change those if they are due since this should be done regardless.
I have a suspicion your converters are fouled & once they are hot it is restricting flow putting pressure back into the cylinder & totally screwing up the air / fuel mixture.
If this is the case, you can change all the parts you want until you get to the converters, none of it will matter.
Do you have a scan tool?
If yes, one that can read live data?
Have you looked at the readings on your O2s switching?
Have you looked at the operating temps of you converters?
Have you checked the misfire counters on each cylinder?
I would agree with Johnny about the random parts.
Some of those things are regular maintenance items like fuel filter & plugs, etc... so yea, change those if they are due since this should be done regardless.
I have a suspicion your converters are fouled & once they are hot it is restricting flow putting pressure back into the cylinder & totally screwing up the air / fuel mixture.
If this is the case, you can change all the parts you want until you get to the converters, none of it will matter.
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