Where's the IAT sensor?
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Fleet Mechanic
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From: va
Where's the IAT sensor?
Where's the Intake air temperature sensor on a 87 F150 4.9 straight six? Does it have two wires, red and black? Also what are the two sensors on the drivers side way back attached to the vavle cover? Thanks guys!
Lead Driver
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From: Concord, NC
Mike, do you have a Haynes manual? It'll show you where most of this stuff is, and even gives you wiring colors in the wiring diagrams at the back. I'm not terribly familiar with the six cylinders but the things on the valve cover are likely the TAD and TAB solonoids for the thermactor system. The IAT is somewhere in the intake manifold, and if it follows the same wiring as other Ford cars and trucks, it should be a yellow wire and a black wire.
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Fleet Mechanic
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From: va
Found three melted hoses
Those three solonoides TAB, TAD and ? on the side of the valve cover have 3 plastic vacuum lines. One goes to air pump and to the juice can and to air pump? All three were melted, just found them today. Would this cause the problems i'm having? Will start with starting fluid and then idle for ten minutes? Runs rich also. Now wont start no matter wha, even after i fixed the three vacuum hoses. It may be flooded, # 1 plug wet. Need new plugs? If these hose were not hooked up for a long time what kind of damage would it do? Also when doing the self test i heard a click from the ECC relay, when i touch the frame by mistake with a bare wire. To check the ECC relay is it ok to test by grounding the meter to the frame and check the three wires for 12 volts? Thanks for your help.
Lead Driver
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From: Concord, NC
Unplug the relay first. Then what you want to test for: one wire should be a ground, one wire should be hot all of the time (12V), one wire should be hot with the ignition on (also 12V), and the other goes to all of the actuators (EVR, TAD, TAB, O2 heater, etc), and two pins on the computer (should have no voltage).
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Fleet Mechanic
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From: va
On mine it has four wires. Red power, blk ground, yellow power ecc and, wht-t blue ignition. Key on all have 12 volts except ground. Relay looks ok. Can i just unplug the three solenoids will the truck run?
Lead Driver
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From: Concord, NC
That's with the relay plugged in, correct? If you unplug the relay, then the truck will not run, unless you jump the terminals with a wire (the relay is just a switch controlled by another lower current wire from a smaller switch).
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Fleet Mechanic
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From: va
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Lead Driver
Joined: Nov 2002
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From: Concord, NC
yes that's what the readings should be when the relay is plugged in. You have a rich running condition - I'm betting the cylinders walls have been washed out, and you aren't getting compression any more. I'd test compression to see if this is the case. The problem does not sound electrical - as long as the fuel pumps work, the computer works (which might be an issue since you can't get any codes) it's not a problem with the relays. Have you tested the MAP sensor?
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Lead Driver
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From: Concord, NC
Of those three solonoids, only one controls something that affects how the engine runs, and that is the EVR. The TAD and TAB only control the air injection system, which has no effect on how the engine runs. I found out yesterday that my multimeter has a frequency tester on it, which can be used to test the MAP sensor (I did it yesterday myself just to see if the multimeter worked for that). You don't need a scope. Patch the vacuum lines and see what happens from there first.
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Fleet Mechanic
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From: va
Map reads below 0 volts???
Originally Posted by EPNCSU2006
Of those three solonoids, only one controls something that affects how the engine runs, and that is the EVR. The TAD and TAB only control the air injection system, which has no effect on how the engine runs. I found out yesterday that my multimeter has a frequency tester on it, which can be used to test the MAP sensor (I did it yesterday myself just to see if the multimeter worked for that). You don't need a scope. Patch the vacuum lines and see what happens from there first.
volt meter set on 10 dcv I put the poss. to the blue wire on the MAP and neg. to the black wire on MAP. Needle drops below zero each time. Should get 5 volts right or close? Thanks
Lead Driver
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From: Concord, NC
Ground should not have voltage. Start testing with the multimeter until you can find where the short is. Test the black wire on the tps, the evp, act, ect, and the sig rtn wire on the diagnostic port for the same 7 volts. They should aslo show this, as they are all connected. If not, the problem is somewhere between the splice and the map sensor. The map voltage on the blue wire should be a steady 2.5V with the sensor plugged in.
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Fleet Mechanic
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From: va
Short to ground
Thanks, I think I have a short to ground on black-white wire. Black-white stripe wire to MAP ,act,ECC data port and evp all have about 5 volts at ground. The black wire with white strip goes to seven places from the ECC. The only one so far that gets no volts is at the TPS at ground. Is the computer bad or basically does the ground wire have a cut and a 5 volt wire is touching it. Is the ECC computer under the D.S. dash? I found the black- white wire above the clutch pedal coming through the firewall. Did i check for ground correctly? Key on not running. . Meter set to 10 dcvI put the neg. wire from the meter to neg on battery and red wire from meter to all black - white wires, at the unpluged sensors on the wirring harness?
Lead Driver
Joined: Nov 2002
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From: Concord, NC
There should be no voltage on the black - white stripe wire at any time. It goes to all the sensors listed, and it should show continuity between all of them. What kind of voltmeter are you using? It would be handy to have one that will beep when testing for continuity. It sounds like there might be a break in the sig rtn splice - test for continuity between all of the sensors and pin 46 on the computer plug (the computer is behind the drivers side kick panel, but the harness is accessed from under the hood, down below the cruise control vacuum servo. I think on the 300's the sig rtn also goes to the clutch safety switch, but I can't say for sure.