Lean Codes and Stumbling - 2001 4.2L
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Joined: May 2012
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Lean Codes and Stumbling - 2001 4.2L
I have a 2001 F150 with a 4.2L V6 that I purchased about a month ago. I bought the truck for the purpose of hauling an 18.5ft Lund on a 1200 mile round trip. I just got back from the trip, so it was able to do that.
However, ever since my first trip home with the truck, it has been throwing the two lean codes and also stumbling under light loads (going up a small hill, etc) at around 57mph. It has recently starting doing the same thing when I first take off in the truck.
I got in contact with the previous owner, who of course knew nothing about the stumbling issue, but who told tell me that he recently changed the fuel pump and fuel filter (past 5 months or so). He told me when I bought the truck that he had just given in a tune up in the past week, so I know the plugs and wires are good (they look new as well).
I initially suspected the MAF so I took this out as far as I could and cleaned it. I didn't have the t25 with the hole in it, so I couldn't get the sensor all the way out, but I could still get at it pretty well and shot it with quite a bit of MAF cleaner. I cleared the codes and drove it for about 25 miles until the codes came back on.
Just this evening, I borrowed a fuel pressure regulator from autozone and checked my fuel pressure. At an idle, with all vacuum lines hooked up, it was about 34psi. When I unplugged the hose running to the FPR, it shot up for 41psi. From what I have found, this seems normal.
Does anyone have any ideas what might be causing this? Did I not get the MAF well enough? I would like to get it fixed so I can sell the truck. Other than this issue, it is a solid, reliable truck. Any help would be appreciated. Thanks in advance.
However, ever since my first trip home with the truck, it has been throwing the two lean codes and also stumbling under light loads (going up a small hill, etc) at around 57mph. It has recently starting doing the same thing when I first take off in the truck.
I got in contact with the previous owner, who of course knew nothing about the stumbling issue, but who told tell me that he recently changed the fuel pump and fuel filter (past 5 months or so). He told me when I bought the truck that he had just given in a tune up in the past week, so I know the plugs and wires are good (they look new as well).
I initially suspected the MAF so I took this out as far as I could and cleaned it. I didn't have the t25 with the hole in it, so I couldn't get the sensor all the way out, but I could still get at it pretty well and shot it with quite a bit of MAF cleaner. I cleared the codes and drove it for about 25 miles until the codes came back on.
Just this evening, I borrowed a fuel pressure regulator from autozone and checked my fuel pressure. At an idle, with all vacuum lines hooked up, it was about 34psi. When I unplugged the hose running to the FPR, it shot up for 41psi. From what I have found, this seems normal.
Does anyone have any ideas what might be causing this? Did I not get the MAF well enough? I would like to get it fixed so I can sell the truck. Other than this issue, it is a solid, reliable truck. Any help would be appreciated. Thanks in advance.
Senior Member
Joined: Jul 2009
Posts: 2,761
Likes: 76
From: Massachusetts
Sounds like intake gaskets to me...
A common issue with the 4.2
Get some carb cleaner and spray it around the gasket area while running the engine and see if you can hear a change in idle... Change=leak
A common issue with the 4.2
Get some carb cleaner and spray it around the gasket area while running the engine and see if you can hear a change in idle... Change=leak