4.9 L running issues
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1st Gear
Joined: Aug 2022
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4.9 L running issues
I wanted to change engines and the new one runs good until warmed up then idles really rough and acts like the transmission doesn’t disengage at a stop and kills the engine. The computer maybe the problem but I changed it for a new one and does the same thing. We’re there two different types of engines for 1992 F-150. 4.9L ?
Logistics Pro
Joined: Nov 2013
Posts: 3,922
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From: Mojave, Ca
I'm not a 4.9.expert, but I'll help if I can. Early 4.9 engines used speed-density for their fuel schedule. In 1994, ford switched to Mass air flow for fuel schedule. The big difference would be the MAP sensor, which is hooked up to the intake manifold on SD engines, and open to the atmosphere on MAF engines. Did you try to check for codes? Take a picture of your engine compartment and post it here.
Fleet Owner
Joined: Oct 2005
Posts: 20,785
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From: Kentucky
You can swap Speed Density for MAF engines and vice versa without a computer change.
Logistics Pro
Joined: Nov 2013
Posts: 3,922
Likes: 1,192
From: Mojave, Ca
Yep. Most of my ford EFI experience is on 5.0L mustangs. My ford trucks are diesel so they're a different animal.
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