mp470 Posted March 31, 2018 Share Posted March 31, 2018 Dug the old girl out of the snow, barely made it home. Stalling at stops... Anyway, my TPS has no function whatsoever at the moment. Wonder if that is part of the issue. No 5V ref., nothing. Two of the wires go right to the MAP sensor, not sure why. One goes towards firewall in a loom under the air box. I may have completely misunderstood where the ECA is, I thought it was on the passenger side near the MAP sensor. How I wish it was a carb... Suggestions, please and thanks. Link to comment Share on other sites More sharing options...
Gary Lewis Posted March 31, 2018 Share Posted March 31, 2018 You can see the wiring here: Electrical/EVTM/1986 EVTM/Electronic Engine Controls. Page 63 says the ECA is near the center of the instrument panel, so what you thought is the ECA is probably the ignition module on the left inner fender. And if there's no voltage to the TPS then that is a big part of your problem. One wire does go to the MAP sensor and another wire goes to a junction of wires close to that sensor. The third wire goes to the ECA, and would have to go through the firewall. But, I don't know how to test the TPS. I'll look around, but hopefully someone who does know will come along soon. Link to comment Share on other sites More sharing options...
85lebaront2 Posted March 31, 2018 Share Posted March 31, 2018 You can see the wiring here: Electrical/EVTM/1986 EVTM/Electronic Engine Controls. Page 63 says the ECA is near the center of the instrument panel, so what you thought is the ECA is probably the ignition module on the left inner fender. And if there's no voltage to the TPS then that is a big part of your problem. One wire does go to the MAP sensor and another wire goes to a junction of wires close to that sensor. The third wire goes to the ECA, and would have to go through the firewall. But, I don't know how to test the TPS. I'll look around, but hopefully someone who does know will come along soon. First issue is to diagnose the lack of the 5V reference circuit, it is not to ground directly, but goes to the sensor signal return. 1985 wiring is different in the color codes, the wire will have a base color and a hash or dot for the second color. 5V reference is circuit #351 and should be orange with white and comes from pin #26 of the EEC, signal return is circuit #359 and should be brown or black with white and is pin#46 on the EEC. These wires go to the TPS, EGR position sensor and MAP sensor. Testing, in order to get a good test on the TPS, you need to unplug it and using an analog multimeter (I have a cheap one I bought at Autozone) measure first from the black with white to the orange with white, I do not have the actual resistance value handy, I do have a chart for the voltage vs rotation angle, which is tested with it connected and key on, engine off and measured at the dark green/light green wire. On yours, closed throttle needs to be as close to 1.0V measured to the signal return side or the system literally goes batshit crazy trying to run. Best way to read the voltages with the connectors plugged together, use paper clips, and slide a straightened leg carefully through the back seal on the connector until it hits the pin or socket depending on which side you are on. Good luck with it! Link to comment Share on other sites More sharing options...
Gary Lewis Posted March 31, 2018 Share Posted March 31, 2018 First issue is to diagnose the lack of the 5V reference circuit, it is not to ground directly, but goes to the sensor signal return. 1985 wiring is different in the color codes, the wire will have a base color and a hash or dot for the second color. 5V reference is circuit #351 and should be orange with white and comes from pin #26 of the EEC, signal return is circuit #359 and should be brown or black with white and is pin#46 on the EEC. These wires go to the TPS, EGR position sensor and MAP sensor. Testing, in order to get a good test on the TPS, you need to unplug it and using an analog multimeter (I have a cheap one I bought at Autozone) measure first from the black with white to the orange with white, I do not have the actual resistance value handy, I do have a chart for the voltage vs rotation angle, which is tested with it connected and key on, engine off and measured at the dark green/light green wire. On yours, closed throttle needs to be as close to 1.0V measured to the signal return side or the system literally goes batshit crazy trying to run. Best way to read the voltages with the connectors plugged together, use paper clips, and slide a straightened leg carefully through the back seal on the connector until it hits the pin or socket depending on which side you are on. Good luck with it! And now we know. I'll get the '85 wire colors off my EVTM in a bit. Link to comment Share on other sites More sharing options...
Gary Lewis Posted March 31, 2018 Share Posted March 31, 2018 And now we know. I'll get the '85 wire colors off my EVTM in a bit. The 1985 EVTM shows: Circuit #351 is Orange/white and goes from the TPS to the EGR valve position sensor, pin 26 on the ECA, and the MAP sensor #355 is Dark green/Light green and goes to pin 47 on the ECA #359 is Black/White and goes to splice S168 and thence to pin 46 on the ECA Link to comment Share on other sites More sharing options...
85lebaront2 Posted March 31, 2018 Share Posted March 31, 2018 The 1985 EVTM shows: Circuit #351 is Orange/white and goes from the TPS to the EGR valve position sensor, pin 26 on the ECA, and the MAP sensor #355 is Dark green/Light green and goes to pin 47 on the ECA #359 is Black/White and goes to splice S168 and thence to pin 46 on the ECA Thanks Gary, I pulled the colors off the EEC pinout information I have from AllData, which supposedly is taken from OEM manuals. Link to comment Share on other sites More sharing options...
Gary Lewis Posted March 31, 2018 Share Posted March 31, 2018 Thanks Gary, I pulled the colors off the EEC pinout information I have from AllData, which supposedly is taken from OEM manuals. Oh! I thought you were saying you needed the wire colors. Link to comment Share on other sites More sharing options...
85lebaront2 Posted March 31, 2018 Share Posted March 31, 2018 Oh! I thought you were saying you needed the wire colors. If you read through, I gave the wire colors as I had them, my info was wrong on #359, everything else matched. Link to comment Share on other sites More sharing options...
mp470 Posted March 31, 2018 Author Share Posted March 31, 2018 First issue is to diagnose the lack of the 5V reference circuit, it is not to ground directly, but goes to the sensor signal return. 1985 wiring is different in the color codes, the wire will have a base color and a hash or dot for the second color. 5V reference is circuit #351 and should be orange with white and comes from pin #26 of the EEC, signal return is circuit #359 and should be brown or black with white and is pin#46 on the EEC. These wires go to the TPS, EGR position sensor and MAP sensor. Testing, in order to get a good test on the TPS, you need to unplug it and using an analog multimeter (I have a cheap one I bought at Autozone) measure first from the black with white to the orange with white, I do not have the actual resistance value handy, I do have a chart for the voltage vs rotation angle, which is tested with it connected and key on, engine off and measured at the dark green/light green wire. On yours, closed throttle needs to be as close to 1.0V measured to the signal return side or the system literally goes batshit crazy trying to run. Best way to read the voltages with the connectors plugged together, use paper clips, and slide a straightened leg carefully through the back seal on the connector until it hits the pin or socket depending on which side you are on. Good luck with it! I use sewing T-pins, they can also pierce the wire gently if necessary. So, the only wire that I traced back to the EEC is the dark green one strangely. Both the orange and black/white were traced to the MAP sensor. I assumed from this that this green wire would be the 5V reference since it's the only one going to the EEC. Not a hint of voltage on it backprobing the EEC pin (not sure which pin number, just used continuity and jumper wire to trace). Very confusing. I've got the Haynes manual but they're not terribly helpful since they show diagrams and wire colors from sometimes only specific years and models and they do vary quite a bit. Edit, oops, had to refresh the page to see the newest posts. Back to it. Link to comment Share on other sites More sharing options...
85lebaront2 Posted March 31, 2018 Share Posted March 31, 2018 I use sewing T-pins, they can also pierce the wire gently if necessary. So, the only wire that I traced back to the EEC is the dark green one strangely. Both the orange and black/white were traced to the MAP sensor. I assumed from this that this green wire would be the 5V reference since it's the only one going to the EEC. Not a hint of voltage on it backprobing the EEC pin (not sure which pin number, just used continuity and jumper wire to trace). Very confusing. I've got the Haynes manual but they're not terribly helpful since they show diagrams and wire colors from sometimes only specific years and models and they do vary quite a bit. Edit, oops, had to refresh the page to see the newest posts. Back to it. Try not to pierce the insulation, it will allow moisture in and corrode the wires. Orange/white is 5V reference, remember to measure to black/white not ground. The dark green may have had a light green 33 years ago, that is the TPS output and it should be around 1 volt to the black/white at closed throttle, rising to 4+ at WOT. If you are getting no voltage on the green wire, TPS is probably bad, and I don't envy you changing it. Haynes manuals, if they are on regular paper can be used in lieu of a Sears catalog as a TP substitute, especially when it comes to wiring. Link to comment Share on other sites More sharing options...
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