Extremely low Vref and running extremely rich
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Cross-Country
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Extremely low Vref and running extremely rich
I’m working on a 1994 f150, 5.0, 5 speed, and speed density, for a buddy of mine. We’re having the trouble of it running extremely rich and in turn very poor. It has new plugs, wire, and cap as well as a new TPS, IAC, and o2 sensor. Tested the Vref in two spots and both were around .34v. So I found and removed the ecu because I’ve heard of the capacitors going bad ans causing problems. (It is a JOY0 ecu). I took off the front and back covers and found all three capacitors were leaking and had gone bad. So I replaced those and I’m still having trouble. The places I tested the reference volts at the orange wire on the tps (at its highest I got .34 volts) and on the egr plug (I don’t remember wire color but had the same reading as the tps wire). At the green wire I can get around .01 v at closed throttle and while opening the throttle the voltage slowly raises to around .32 or so at wide open. Any help is appreciated and much needed.
Last edited by Wilsalmons; Sep 1, 2023 at 07:08 PM. Reason: Corrections
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Cross-Country
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a lot of the sensors are new and I wouldn’t think a bad sensor would cause the Vref to be so low.
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Hotshot
Joined: Jun 2015
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That sounds like the original air bag steering wheel. At least that is what was in my ‘94 Bronco.
Did I miss where you checked for engine off (KOEO) fault codes before replacing all those sensors and after the computer repair?
Did I miss where you checked for engine off (KOEO) fault codes before replacing all those sensors and after the computer repair?
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Ok so I started unplugging sensors and checking Vref on the egr plug with the brown with a white line wire. The first time I did it, it was at .31. I then unplugged the TPs and it raised to .41 and now it’s staying at that with the TPs plugged in. I also found that with the map sensor unplugged I lose all Vref everywhere. Is that normal. I also found that the middle wire on the map sensor only gets around 5.04 volts when testing ground. The battery is at a steady 11.94 volts. Key on engine off. While on my truck (a 1992 flaireside 5.0 5 speed) I get 12.45 volts with a 12.55 volt battery. Where does the map sensors ground to and how can I check it?
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Cross-Country
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Ok so I started unplugging sensors and checking Vref on the egr plug with the brown with a white line wire. The first time I did it, it was at .31. I then unplugged the TPs and it raised to .41 and now it’s staying at that with the TPs plugged in. I also found that with the map sensor unplugged I lose all Vref everywhere. Is that normal. I also found that the middle wire on the map sensor only gets around 5.04 volts when testing ground. The battery is at a steady 11.94 volts. Key on engine off. While on my truck (a 1992 flaireside 5.0 5 speed) I get 12.45 volts with a 12.55 volt battery. Where does the map sensors ground to and how can I check it?
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My next question is can I swap a different computer into this truck just to test if it is the computer that’s still bad. For example my truck has the W2M computer and the problem child’s computer is a JOY0. Can these computers be swapped or is their other differences that would cause problems.
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it probably wouldn’t be a bad idea but it still doesn’t help the Vref issue. Also it runs so rich that it smokes like diesel and you can smell the gas. I’d like to get the electrical part fixed before I worry about anything else. That’s why I wanted to swap a known good computer to see if that was the issue.
Cargo Master
Joined: Aug 2021
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From: Maryland
Is your ECU relay interchangeable with your fuel pump relay? Might be worth swapping them and looking for corrosion in their sockets.
Does your truck have a smaller gauge wire coming off of your battery negative cable? If so, is it grounded well?
How clean are your battery negative connections?
Does your truck have a smaller gauge wire coming off of your battery negative cable? If so, is it grounded well?
How clean are your battery negative connections?
Fleet Owner
Joined: Oct 2005
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From: Kentucky
I also found that the middle wire on the map sensor only gets around 5.04 volts when testing ground. The battery is at a steady 11.94 volts. Key on engine off. While on my truck (a 1992 flaireside 5.0 5 speed) I get 12.45 volts with a 12.55 volt battery. Where does the map sensors ground to and how can I check it?