85lebaront2 Posted May 1, 2023 Share Posted May 1, 2023 You're looking for exactly 1V (+/- 0.05V) between black and green. Here's a ten year old quote from Bill "on the 1985-86 EFI 302, the TPS voltage is critical. These computers work on absolute voltage, unlike the later ones that work on difference from start value. Archion learned the hard way on his 86 F-150. An aftermarket TPS was nominally in spec at 1.08v at closed throttle. His EGR vent solenoid sounded like a machine gun and the truck wouldn't idle worth a damn it also acted strange even driving. The spec to set the TPS voltage on these is measured between the dark green with light green strip wire and the black with white stripe wire. Orange with white stripe to black with white stripe should be 5.0v. Set voltage is 0.95 to 1.05v, if you cannot get that and have it idle, or you end up backing the screw out until it doesn't touch and still can't get there, the TPS is probably bad. Unfortunately, the only ones that work correctly on these are Motorcraft ones." Gee, I remember that headache. I spent a weekend in Falling Waters WV getting it solved. Maybe Gary could add that into the idle setting information. Link to comment Share on other sites More sharing options...
1986 F150 Posted May 1, 2023 Author Share Posted May 1, 2023 Jeff, Jim, the 1985/86 5.0L EFI system is not like the 1987 up systems, The idle stop screw setting is very touchy on these. The EGR system starts to function just off idle (Matt's drove both of us nuts). In the right front corner behind the battery is a set of solenoid valves: https://forum.garysgaragemahal.com/file/n134972/DSCN1482_copy.jpg Two of them are for the EGR valve, the other two are for the Thermactor system. If the TPS voltage is too high, the EGR pair will chatter and the EGR valve will try to open, which kills the idle, followed by closing where it will pick up again. The idle may be raised to get around this. One item we did discover, aftermarket sensors do not always react the same as OEM Ford ones, he had a Standard TPS and could not get the closed throttle voltage low enough. A Motorcraft one solved the problem. I did not hear any chattering from the EGR solenoid valves. I'll do a voltage check on the TPS. I just can't see the TPS suddenly going out, as like I mentioned before, it idled in gear fine before I replaced a bad TFI module (I had it tested and it was shot). I don't know what else to try, am getting close to the end of my rope. Can't afford to dump much more money into it Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted May 1, 2023 Share Posted May 1, 2023 Jeff, Jim, the 1985/86 5.0L EFI system is not like the 1987 up systems, The idle stop screw setting is very touchy on these. The EGR system starts to function just off idle (Matt's drove both of us nuts). In the right front corner behind the battery is a set of solenoid valves: https://forum.garysgaragemahal.com/file/n134972/DSCN1482_copy.jpg Two of them are for the EGR valve, the other two are for the Thermactor system. If the TPS voltage is too high, the EGR pair will chatter and the EGR valve will try to open, which kills the idle, followed by closing where it will pick up again. The idle may be raised to get around this. One item we did discover, aftermarket sensors do not always react the same as OEM Ford ones, he had a Standard TPS and could not get the closed throttle voltage low enough. A Motorcraft one solved the problem. I did not hear any chattering from the EGR solenoid valves. I'll do a voltage check on the TPS. I just can't see the TPS suddenly going out, as like I mentioned before, it idled in gear fine before I replaced a bad TFI module (I had it tested and it was shot). I don't know what else to try, am getting close to the end of my rope. Can't afford to dump much more money into it I'm never about parts swapping and always about diagnosis. Take some readings from the TPS and if it's out of range slack off the the stop to see if you can get it back where it belongs. The fuel regulator was obviously a big issue that needed replaced before any other trouble shooting. You might find closing the plate up will help since there's not gas going everywhere now. Do you have an accurate meter? Link to comment Share on other sites More sharing options...
1986 F150 Posted May 1, 2023 Author Share Posted May 1, 2023 I'm never about parts swapping and always about diagnosis. Take some readings from the TPS and if it's out of range slack off the the stop to see if you can get it back where it belongs. The fuel regulator was obviously a big issue that needed replaced before any other trouble shooting. You might find closing the plate up will help since there's not gas going everywhere now. Do you have an accurate meter? I have a digital multimeter I bought from a tool bin at my local hardware store a few years ago, it's as accurate as it can be I guess, it'll have to do. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted May 1, 2023 Share Posted May 1, 2023 I'm never about parts swapping and always about diagnosis. Take some readings from the TPS and if it's out of range slack off the the stop to see if you can get it back where it belongs. The fuel regulator was obviously a big issue that needed replaced before any other trouble shooting. You might find closing the plate up will help since there's not gas going everywhere now. Do you have an accurate meter? I have a digital multimeter I bought from a tool bin at my local hardware store a few years ago, it's as accurate as it can be I guess, it'll have to do. Digital is good as long as the battery is fresh. Let us know what you find! Link to comment Share on other sites More sharing options...
grumpin Posted May 1, 2023 Share Posted May 1, 2023 Jeff, Jim, the 1985/86 5.0L EFI system is not like the 1987 up systems, The idle stop screw setting is very touchy on these. The EGR system starts to function just off idle (Matt's drove both of us nuts). In the right front corner behind the battery is a set of solenoid valves: https://forum.garysgaragemahal.com/file/n134972/DSCN1482_copy.jpg Two of them are for the EGR valve, the other two are for the Thermactor system. If the TPS voltage is too high, the EGR pair will chatter and the EGR valve will try to open, which kills the idle, followed by closing where it will pick up again. The idle may be raised to get around this. One item we did discover, aftermarket sensors do not always react the same as OEM Ford ones, he had a Standard TPS and could not get the closed throttle voltage low enough. A Motorcraft one solved the problem. I did not hear any chattering from the EGR solenoid valves. I'll do a voltage check on the TPS. I just can't see the TPS suddenly going out, as like I mentioned before, it idled in gear fine before I replaced a bad TFI module (I had it tested and it was shot). I don't know what else to try, am getting close to the end of my rope. Can't afford to dump much more money into it You said you replaced the TFI Module. It could be bad out of the box. Can't trust aftermarket parts anymore. I'd be leary of OEM anymore. Link to comment Share on other sites More sharing options...
1986 F150 Posted May 1, 2023 Author Share Posted May 1, 2023 Digital is good as long as the battery is fresh. Let us know what you find! TPS test results: 5 volts between orange wire and black wire 1 volt between dark green wire and black wire Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted May 1, 2023 Share Posted May 1, 2023 Digital is good as long as the battery is fresh. Let us know what you find! TPS test results: 5 volts between orange wire and black wire 1 volt between dark green wire and black wire More good news! I might try to back the idle down to see if that keeps the transmission from loading the engine in gear. Curb idle for automatics is shown in gear (with the vacuum advance capped and wheels chocked) on the emissions/vacuum sticker attached to the radiator support. But you might look to the 'manual in neutral' setting to get an idea of engine speed if you can't yet do it engaged in drive. Link to comment Share on other sites More sharing options...
vjsimone Posted August 30, 2023 Share Posted August 30, 2023 Digital is good as long as the battery is fresh. Let us know what you find! TPS test results: 5 volts between orange wire and black wire 1 volt between dark green wire and black wire Hello Jeff, (following) how is this going ? Link to comment Share on other sites More sharing options...
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