Map sensor wire diagram??
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Map sensor wire diagram??
I have a 1991 f150 5.0
my issue is a surging idle. I replaced the iac. The ect. The throttle body sensor is going to be replaced while i clean the throttle body. I used a propane torch and no vaccum leaks but I tested my purge valve and it is fried shut. I back probed the map sensor and I'm getting 0 volts on the continuous but i am getting 8 volts when testing the ground. Where is the ecu and is there a diagram I can see for testing to see if theres a brake in the wire.
also I replaced the sensors because they were all bad.
my issue is a surging idle. I replaced the iac. The ect. The throttle body sensor is going to be replaced while i clean the throttle body. I used a propane torch and no vaccum leaks but I tested my purge valve and it is fried shut. I back probed the map sensor and I'm getting 0 volts on the continuous but i am getting 8 volts when testing the ground. Where is the ecu and is there a diagram I can see for testing to see if theres a brake in the wire.
also I replaced the sensors because they were all bad.
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Joined: Jan 2018
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From: Memphis, TN, Earth, Milky Way
If all those components were actually bad, the engine probably wouldn't have run. If you don't have a wiring diagram, how did you test them to determine that they were bad? Spraying flammables around a running engine is NOT a test for anything but your luck. Use a mechanic's stethoscope (or 3' of garden hose) to listen - it's much more precise, cheaper, & safer.
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It's hard to tell what you're measuring & why, without knowing where each meter probe is, and whether the engine is running, key-on, or key-off during the readings. IDK what you mean by "on the continuous". How exactly are you testing "the ground", and which ground point are you checking? If you don't have a Haynes manual, get one. Eventually, you need to read it cover-to-cover at least once so you know what's in it & where to find things. But read this caption first:
(phone app link)
This shows the EEC pinout:
(phone app link)
This caption explains how to test each sensor:
(phone app link)
This shows where the EEC is:
(phone app link)
You can find some wiring diagrams here:
www.bbbind.com/tsb-wiring-diagrams-database/
(phone app link)
It's hard to tell what you're measuring & why, without knowing where each meter probe is, and whether the engine is running, key-on, or key-off during the readings. IDK what you mean by "on the continuous". How exactly are you testing "the ground", and which ground point are you checking? If you don't have a Haynes manual, get one. Eventually, you need to read it cover-to-cover at least once so you know what's in it & where to find things. But read this caption first:
(phone app link)
This shows the EEC pinout:
(phone app link)
This caption explains how to test each sensor:
(phone app link)
This shows where the EEC is:
(phone app link)
You can find some wiring diagrams here:
www.bbbind.com/tsb-wiring-diagrams-database/
Thread Starter
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Joined: Jan 2020
Posts: 60
Likes: 8
For the IAC was recommended to just replace due to it being inexpensive and seemed to help a lot with the surging idle but not fix it. The ect was broke because I noticed that it was ripped in half when someone on the form mentioned the ect due to it being only when at operating temp.
the tps is probably faulty because I back probed it and idle gave out 1 volt while full throttle gave out 3.8. I was told that using the propane fumes will get sucked into the hose and you could hear the idle change? For the map sensor you have 3 wires red with 5 volts continuously, green for the signal that will change as you throttle, and the black for the ground. I back probed the red wire and the black wire and got 0 volts. I also tried the green(middle) and the black and got 0 volts while the key is on but engine is off.I then pulled the connector and tried testing from the connector that goes to the computer and it was getting 0 volts too. I need the wire diagram to see if the EEC is sending 5 volts and if it is I want to check if there is a break in the wire. For the ground I was told to put a neg lead to the ground and the pos to the battery and if it gets a voltage it means that the ground is good.
the tps is probably faulty because I back probed it and idle gave out 1 volt while full throttle gave out 3.8. I was told that using the propane fumes will get sucked into the hose and you could hear the idle change? For the map sensor you have 3 wires red with 5 volts continuously, green for the signal that will change as you throttle, and the black for the ground. I back probed the red wire and the black wire and got 0 volts. I also tried the green(middle) and the black and got 0 volts while the key is on but engine is off.I then pulled the connector and tried testing from the connector that goes to the computer and it was getting 0 volts too. I need the wire diagram to see if the EEC is sending 5 volts and if it is I want to check if there is a break in the wire. For the ground I was told to put a neg lead to the ground and the pos to the battery and if it gets a voltage it means that the ground is good.
Last edited by Fettersp; Jan 6, 2020 at 10:12 PM.
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Joined: Jan 2018
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From: Memphis, TN, Earth, Milky Way
A dome light bulb is inexpensive - are you going to replace that, too? If it's not the cause of the problem, there's no point replacing it - that applies to bulbs, sensors, and actuators (like the IAC, which is NOT the primary control for idle speed).
Your descriptions of what you did are vague, and not the correct techniques. Read the Haynes, learn how to use a digital multimeter, and don't replace any part unless it's due on the maintenance schedule, or it fails a published (NOT anecdotal on the interwebz) test. When you replace a part, replace it with the BEST one you can find - not necessarily the cheapest or quickest.
Your descriptions of what you did are vague, and not the correct techniques. Read the Haynes, learn how to use a digital multimeter, and don't replace any part unless it's due on the maintenance schedule, or it fails a published (NOT anecdotal on the interwebz) test. When you replace a part, replace it with the BEST one you can find - not necessarily the cheapest or quickest.