EFI 4.9 problems
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New User
Joined: Jan 2007
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EFI 4.9 problems
Well guys, i'm stumped. My 91' f-150, (4.9 / 5sd man.) still misses, but it comes and goes. Allways does it when it starts, then it's fine, till I decelerate then it bucks like it wants to die. Changed plugs and wires twice, cap & rotor, changed coil, and ignition module on dist. The problem is it seems like an electrical shutdown when it happens, not just one cylinder misses, they all miss, enough to kill the engine or make the whole truck buck. Starting to look into the EGR system inputs to the computer. Would an oxygen sensor and or EGR position sensor screw up the mixture enough while decelerating to kill to engine? I checked engine vacume and fuel rail pressure, and they are ok. Any ideas or inputs are appreciated, cause i've 'bout run out of steam on this project. Thanks,Dan!
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Joined: Mar 2004
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From: Stockbridge Michigan
Check for a sticking EGR valve also. I don't think the egr postion sensor would make it run like that but it might. check to make sure the pipe that goes from the exhaust manifold to the EGR valve isn't rusted out. On my 96 the egr postion sensor reads off of this tube by two rubber hoses connected to it and if the pipe was rusted out there woulkd be no backpressure in the pipe so the sensor and ECM would think the egr is open all the time.
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Finally another clue! I ran the codes again and got a 213 when i did the KOER test. before I was just getting an engine coolant temp. sender code, and a 111 system pass code, but I already know i need a temp. sender. The 213 says a spark output circuit short was detected. AND at the same time it stuttered, my blower motor shut off and the rear antilock light comes on, hmmmm says I. I wiggled the key switch and the blower motor turned back on. Could a short in the column to the ignition switch be causing all these headaches? Reguardless, I think i'm going to replace the switch in the column tomorrow. By the way, you were right, my egr valve was stuck open, but didn't yield any dramatic results. But good to know! A new exhaust from manifolds back is next on the list. I will let you guys know if the switch fixes her tomorrow. thanks, Dan
