LastDeadLast Posted December 5, 2022 Share Posted December 5, 2022 Many thanks! I will use that approach and also order the reader!!! My 85 EFI doesn't have a check engine light. YMMV. Shannon Link to comment Share on other sites More sharing options...
85lebaront2 Posted December 5, 2022 Share Posted December 5, 2022 The erratic idle may be the same thing my son had on his 1986 F150. His problem was an aftermarket TPS. The idle stop screw on these trucks is adjusted based on a voltage reading. If the voltage is a little high the EGR vacuum and vent solenoids will chatter as the system tries to adjust things. Link to comment Share on other sites More sharing options...
mat in tn Posted December 5, 2022 Share Posted December 5, 2022 The erratic idle may be the same thing my son had on his 1986 F150. His problem was an aftermarket TPS. The idle stop screw on these trucks is adjusted based on a voltage reading. If the voltage is a little high the EGR vacuum and vent solenoids will chatter as the system tries to adjust things. please use motorcraft tps (and other electronics ) only. i only say this because of the problems we have had in the year in the shop with "replacement parts". it seems that there is a specific response/range that the ecu works the best with . just a theory for me but we have ended up fixing many situations when we backed up to motorcraft parts. and tps is one of the biggest. have had a few iac's also and one now that i believe will be solved with a coolant temp sensor but it has not been back to me yet. Link to comment Share on other sites More sharing options...
Socnarftrucks Posted December 5, 2022 Author Share Posted December 5, 2022 The erratic idle may be the same thing my son had on his 1986 F150. His problem was an aftermarket TPS. The idle stop screw on these trucks is adjusted based on a voltage reading. If the voltage is a little high the EGR vacuum and vent solenoids will chatter as the system tries to adjust things. Interesting. I do have an authentic Chinese imitation one from Autozone. I wonder, what if I delete the EGR?…. One way to find out….. Link to comment Share on other sites More sharing options...
85lebaront2 Posted December 5, 2022 Share Posted December 5, 2022 please use motorcraft tps (and other electronics ) only. i only say this because of the problems we have had in the year in the shop with "replacement parts". it seems that there is a specific response/range that the ecu works the best with . just a theory for me but we have ended up fixing many situations when we backed up to motorcraft parts. and tps is one of the biggest. have had a few iac's also and one now that i believe will be solved with a coolant temp sensor but it has not been back to me yet. Mat, my point exactly! "close enough" will work sometimes, but not always. 1987 up systems are not as sensitive as they take the voltage at startup and use that for closed throttle, the EGR controls also changed from two solenoid valves to a single pulse width valve. The other item I have found is the EVP sensor (EGR Valve Position), I have had a number of them where the plunger was too long, not by much, maybe 1/16-3/32" too long so the computer thought it was open when it wasn't. A little work with a grinder and problem solved. Link to comment Share on other sites More sharing options...
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