Problems after mods
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New User
Joined: Sep 2017
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Problems after mods
Okay. I'm having a major malfunction. I built a true dual exhaust system for my 94 f-150. Its got a 5.0 block and heads out of a 93 t bird. I used hooker long tube block huggers, magnaflow high flow converters, flowmaster 44s, and 2.5 inch plumbing. I put the oxygen sensor back in the same location as the old one.
Now the problem. My long term fuel trim is staying at a -56, which causes the af ratio to go completely rich. I assume this is why I keep blowing o2 sensors. The motor lopes, dies at times, gets crappy fuel mileage, and has no power, especially on hills. I heard through the grapevine that I need to convert to mass air flow sensor because it is a speed density motor. Will this work? And where can I get a conversion kit that doesnt cost an arm and a leg? Any help would be greatly appreciated.
Now the problem. My long term fuel trim is staying at a -56, which causes the af ratio to go completely rich. I assume this is why I keep blowing o2 sensors. The motor lopes, dies at times, gets crappy fuel mileage, and has no power, especially on hills. I heard through the grapevine that I need to convert to mass air flow sensor because it is a speed density motor. Will this work? And where can I get a conversion kit that doesnt cost an arm and a leg? Any help would be greatly appreciated.
Elder User
Joined: Dec 2016
Posts: 854
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From: Mid Missouri
Your problem sounds eerily similar to mine after
the swap to 351. What heads are those off the T-bird? Did you check for correct push rod length? They could be too long causing the valves to stick open.
the swap to 351. What heads are those off the T-bird? Did you check for correct push rod length? They could be too long causing the valves to stick open.
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New User
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The block and heads are stock to the t bird. I bolted everything else from my other engine on it. The pistons hypereutectic and the cam is the 351 firing order. That's the only difference other than the plenum.
Junior User
Joined: Dec 2018
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I had a 94 f150 with ported heads and a trick flow stage 1 that had a plainly noticeable lope with long tube hedman headers and 3 inch dual open exhaust out the back. I had the o2 sensor only into 1 exhaust bank. I really didnt have many driveability issues and it got about 12 mpg with 35 12.50s. I think something else is up. Do you have a low temp thermostat in it? Is the coolant temp sensor working? There should be 2 temp sensors in play one for the gauge and one for the ecu. Thermostat stuck open?
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I have the stock temp thermostat, the cts is working within specs and the thermostat isnt stuck open. It open and closes at the proper temp.
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