Emergency help needed
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Junior User
Joined: Feb 2013
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Emergency help needed
Hey guys, Im currently in a bit of a pickle. I recently replaced the tps/iac in hopes of fixing my idle/start up issue. It helped a bit but today I started to mess around with the MAP sensor. I pulled it off and started up the truck. It ran great (best start up thus far). Just plugged the old MAP sensor back in after just a few minuets and now nothing. The engine turns over fine it just wont fire. Any suggestions? Im a bit stranded right now and need to have this figured out by this afternoon 
. Any help would be appreciated.
Truck specs are in my signature.
Thanks guys.
. Any help would be appreciated. Truck specs are in my signature.
Thanks guys.
Postmaster
Joined: Jun 2014
Posts: 3,206
Likes: 3
From: Oakhust NJ Jersey Shore
You say it wont fire, do you have spark? fuel? IAC, TPS, MAPS, are all needed for the computer to learn and adjust while driving, as far as starting, they dont do much, same with the o2's IAT, CTS you can replace parts all day but you need to get the important one that effects the starting of the truck, Whats your fuel pressure, did you replace the fuel filter recently? pull the vacuum line on the pressure regulator make sure no fuel is leaking out, check the ignition, could be a bad pick up or module. I know the coil connections suck on those 4.9's. Did you do what ford calls a wiggle test? check all the grounds, especially the ones on the fender well next to the battery, wiggle the wires and check the connections. If you have to get this thing going you better start going. 
Thread Starter
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Junior User
Joined: Feb 2013
Posts: 58
Likes: 0
You say it wont fire, do you have spark? fuel? IAC, TPS, MAPS, are all needed for the computer to learn and adjust while driving, as far as starting, they dont do much, same with the o2's IAT, CTS you can replace parts all day but you need to get the important one that effects the starting of the truck, Whats your fuel pressure, did you replace the fuel filter recently? pull the vacuum line on the pressure regulator make sure no fuel is leaking out, check the ignition, could be a bad pick up or module. I know the coil connections suck on those 4.9's. Did you do what ford calls a wiggle test? check all the grounds, especially the ones on the fender well next to the battery, wiggle the wires and check the connections. If you have to get this thing going you better start going.
Thread Starter
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Junior User
Joined: Feb 2013
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Well it seems that in the time I had the MAP sensor unplugged I lost spark. I tried unplugging the sensor again and no go.
Lead Driver
Joined: Aug 2006
Posts: 5,670
Likes: 13
From: Sand Lake, MI
Just to be clear you did check and it has no spark correct?
Appears that is the case, did you test for power to the positive side of the coil key in "Start" and "Run" positions? Should be a white lt blu wire and dark green wires, you wanna test for power at the white lt blu wire key turned to both those two positions.
If not might need to back up further but that's a quick easy to get to starting point.
Make sure that wire shows full battery juice (12v plus for example) and those connections at the coil are corrosion free.
The fact you lost spark at that moment would be more coincidence over any cause and effect what you did.
Appears that is the case, did you test for power to the positive side of the coil key in "Start" and "Run" positions? Should be a white lt blu wire and dark green wires, you wanna test for power at the white lt blu wire key turned to both those two positions.
If not might need to back up further but that's a quick easy to get to starting point.
Make sure that wire shows full battery juice (12v plus for example) and those connections at the coil are corrosion free.
The fact you lost spark at that moment would be more coincidence over any cause and effect what you did.
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