sdhorton Posted April 6, 2020 Share Posted April 6, 2020 I have read all the information I can find and nothing has led me to a cure for this monster. Our youth shooting club was donated this truck to use or to sell and I cannot get it to run right. 1986 F150 5.0 auto 4x4. starts and runs, Idles fair, WOT fair everything else poor. At idle if you jab throttle it will die instantly. We have run KOEO and KOER test, have located and cleared several items. Replace TPS tested and cleaned IAC, Tested timing and advance functions, tested spark on all cyl, compression is somewhat weak and erratic running from 75 to 123 but the engine hasn't been run hardly at all for several years. Exhaust system is open, have replaced both fuel pumps with new. pressure running at about 34lb. I would like to find a trouble shooting flow chart or tree chart. I do not have a manual and right now cannot get a hard copy sent to me very well. What else should we be looking at? I am about to run it off the end of the dock! Thanks Shane Link to comment Share on other sites More sharing options...
85lebaront2 Posted April 6, 2020 Share Posted April 6, 2020 Ok, first item, TPS, aftermarket or Motorcraft? My so and I went through a nightmare on his 86 F150, part of the problem was the aftermarket TPS. The 1986 system expects to see 1.0 V at closed throttle, I believe +/- .05 volts, and at 1.10 volts the EGR system comes in, meaning his was chattering the solenoid valves and surging at idle. On your frame, just behind the high pressure pump is a reservoir and on dual tank models a switching valve. In the bottom of that is filter for the inlet of the high pressure pump. Does the truck have a "check engine" light? Or it may say "emissions", if it does codes can be read through that. Unfortunately most parts stores can only read OBD-II systems and that is an OBD-I system. The fact that you have been able to read them is a plus. I will see if I can find a good diagnostic chart and scan it so Gary can put it on the site. Link to comment Share on other sites More sharing options...
Frank Wyatt Posted April 6, 2020 Share Posted April 6, 2020 Ok, first item, TPS, aftermarket or Motorcraft? My so and I went through a nightmare on his 86 F150, part of the problem was the aftermarket TPS. The 1986 system expects to see 1.0 V at closed throttle, I believe +/- .05 volts, and at 1.10 volts the EGR system comes in, meaning his was chattering the solenoid valves and surging at idle. On your frame, just behind the high pressure pump is a reservoir and on dual tank models a switching valve. In the bottom of that is filter for the inlet of the high pressure pump. Does the truck have a "check engine" light? Or it may say "emissions", if it does codes can be read through that. Unfortunately most parts stores can only read OBD-II systems and that is an OBD-I system. The fact that you have been able to read them is a plus. I will see if I can find a good diagnostic chart and scan it so Gary can put it on the site. Bill has some good insight there on the TPS. Two other quick observations, 34 lbs sounds low to me on the fuel pressure, so check the filter in the reservoir like bill said, and also look at the fuel pressure regulator. Check the vacuum line as it could be cracked, though I couldn't tell you how it would be affected. Also the compression readings seem low and uneven, but a little oil in the low cylinders and rerunning the compression test could give higher numbers. Link to comment Share on other sites More sharing options...
sdhorton Posted April 6, 2020 Author Share Posted April 6, 2020 Ok, first item, TPS, aftermarket or Motorcraft? My so and I went through a nightmare on his 86 F150, part of the problem was the aftermarket TPS. The 1986 system expects to see 1.0 V at closed throttle, I believe +/- .05 volts, and at 1.10 volts the EGR system comes in, meaning his was chattering the solenoid valves and surging at idle. On your frame, just behind the high pressure pump is a reservoir and on dual tank models a switching valve. In the bottom of that is filter for the inlet of the high pressure pump. Does the truck have a "check engine" light? Or it may say "emissions", if it does codes can be read through that. Unfortunately most parts stores can only read OBD-II systems and that is an OBD-I system. The fact that you have been able to read them is a plus. I will see if I can find a good diagnostic chart and scan it so Gary can put it on the site. I will check on the brand of the TPS, it is likely NOT a ford part. Is there enough slot on the mounts to get much adjustment? I have read about that filter before, I will have to put it back up on the hoist and look for it. There is an inline filter, and of course the filters or inlet screen on the new pumps we installed. We don't have a code reader, we have been reading the flash codes. The only code we are getting now I think is a 552 which is the airA and airB solenoids system I believe. Link to comment Share on other sites More sharing options...
85lebaront2 Posted April 6, 2020 Share Posted April 6, 2020 I will check on the brand of the TPS, it is likely NOT a ford part. Is there enough slot on the mounts to get much adjustment? I have read about that filter before, I will have to put it back up on the hoist and look for it. There is an inline filter, and of course the filters or inlet screen on the new pumps we installed. We don't have a code reader, we have been reading the flash codes. The only code we are getting now I think is a 552 which is the airA and airB solenoids system I believe. Ok, no adjustment on the TPS, no slots, base idle is set with the IAC disconnected if I remember correctly, but spec is based on voltage at the TPS. Filter is in the base of the reservoir, it unscrews for access. I was trying to find the thread on FTE where my son posted the PN for it, but no luck. Link to comment Share on other sites More sharing options...
myrl883 Posted April 6, 2020 Share Posted April 6, 2020 Ok, no adjustment on the TPS, no slots, base idle is set with the IAC disconnected if I remember correctly, but spec is based on voltage at the TPS. Filter is in the base of the reservoir, it unscrews for access. I was trying to find the thread on FTE where my son posted the PN for it, but no luck. Motorcraft FG-848. Now obsolete, but a parts store should be able to cross reference it. Only 1985 and early '86s had a filter in there. If there is no filter, the cover will be marked "DO NOT REMOVE". Link to comment Share on other sites More sharing options...
sdhorton Posted April 6, 2020 Author Share Posted April 6, 2020 Motorcraft FG-848. Now obsolete, but a parts store should be able to cross reference it. Only 1985 and early '86s had a filter in there. If there is no filter, the cover will be marked "DO NOT REMOVE". I feel sort of silly, the truck we are working on is a 91 model not an 86 as I earlier said. sorry for the screw up. I am also fighting similar problems on an 06 Chev and got them crossed up. Link to comment Share on other sites More sharing options...
sdhorton Posted April 6, 2020 Author Share Posted April 6, 2020 Ok, no adjustment on the TPS, no slots, base idle is set with the IAC disconnected if I remember correctly, but spec is based on voltage at the TPS.Filter is in the base of the reservoir, it unscrews for access. I was trying to find the thread on FTE where my son posted the PN for it, but no luck.Bill, did you get the message that I gave you the wrong year model on that truck? I am working on another rig too and got them crossed up. This F150 is a 91 model with the 5.0 engine. Sorry if I wasted your time. Shane From: 85lebaront2 [via Bullnose Enthusiasts] <redacted_email_address>Sent: Monday, April 6, 2020 12:46 PMTo: sdhorton <redacted_email_address>Subject: Re: 86 F150 5.0 running poorly Ok, no adjustment on the TPS, no slots, base idle is set with the IAC disconnected if I remember correctly, but spec is based on voltage at the TPS. Filter is in the base of the reservoir, it unscrews for access. I was trying to find the thread on FTE where my son posted the PN for it, but no luck. Bill Profile "Getting old is inevitable, growing up is optional" Darth Vader 1986 F-350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 1994 Taurus LX Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413 If you reply to this email, your message will be added to the discussion below:http://forum.garysgaragemahal.com/86-F150-5-0-running-poorly-tp55861p55886.html To unsubscribe from 86 F150 5.0 running poorly, click here.NAML https://ipmcdn.avast.com/images/icons/icon-envelope-tick-round-orange-animated-no-repeat-v1.gif Virus-free. www.avast.com Link to comment Share on other sites More sharing options...
85lebaront2 Posted April 6, 2020 Share Posted April 6, 2020 I feel sort of silly, the truck we are working on is a 91 model not an 86 as I earlier said. sorry for the screw up. I am also fighting similar problems on an 06 Chev and got them crossed up. Well a 1991 is a much improved system from a 1986. Are you saying that an 06 French truck reminds you of a 1986 Ford? Ok, 1991 I think if you can find someone with a fair scan tool it may be able to read live data when running. Two of the major changes in addition to pin changes on the EEC are a speed input and a single duty cycle EGR control valve. You had me concerned when you posted a 3 digit code, 1986 only had 2 digit codes. 1990-up have a fuel pump module so no extra frame mounted pump. That TPS does not need to be right at 1 volt, the EEC will read the value when cranking and set that as idle/closed throttle. Shane, maybe these will help, they are from my AllData Link to comment Share on other sites More sharing options...
sdhorton Posted April 8, 2020 Author Share Posted April 8, 2020 Well a 1991 is a much improved system from a 1986. Are you saying that an 06 French truck reminds you of a 1986 Ford? Ok, 1991 I think if you can find someone with a fair scan tool it may be able to read live data when running. Two of the major changes in addition to pin changes on the EEC are a speed input and a single duty cycle EGR control valve. You had me concerned when you posted a 3 digit code, 1986 only had 2 digit codes. 1990-up have a fuel pump module so no extra frame mounted pump.That TPS does not need to be right at 1 volt, the EEC will read the value when cranking and set that as idle/closed throttle.Shane, maybe these will help, they are from my AllDataMaking some progress here, the EGR sensor is quite a ways out of whack and I am trying to figure out how the thermistor valve is supposed to be actuated. I have no vac to the EGR at idle like it is supposed to but I have no vacuum at higher rpm either. The red vac tube to the thermistor has vac but the valve is not opening. I can ground the wire on it and then it opens so I think the valve is OK I just don’t know what triggers it. From: 85lebaront2 [via Bullnose Enthusiasts] <redacted_email_address>Sent: Monday, April 6, 2020 3:50 PMTo: sdhorton <redacted_email_address>Subject: Re: 86 F150 5.0 running poorly Well a 1991 is a much improved system from a 1986. Are you saying that an 06 French truck reminds you of a 1986 Ford? Ok, 1991 I think if you can find someone with a fair scan tool it may be able to read live data when running. Two of the major changes in addition to pin changes on the EEC are a speed input and a single duty cycle EGR control valve. You had me concerned when you posted a 3 digit code, 1986 only had 2 digit codes. 1990-up have a fuel pump module so no extra frame mounted pump. That TPS does not need to be right at 1 volt, the EEC will read the value when cranking and set that as idle/closed throttle.http://forum.garysgaragemahal.com/file/n55908/DTC_codes_copy.jpghttp://forum.garysgaragemahal.com/file/n55908/Pinpoint_test_TA1_copy.jpghttp://forum.garysgaragemahal.com/file/n55908/Pinpoint_test_KM40_copy.jpghttp://forum.garysgaragemahal.com/file/n55908/Pinpoint_test_TA8_copy.jpg Shane, maybe these will help, they are from my AllData Bill Profile "Getting old is inevitable, growing up is optional" Darth Vader 1986 F-350 460 converted to MAF/SEFI, E4OD 12X3 1/2 rear brakes, traction loc 3:55 gear, 160 amp 3G alternator Wife's 2011 Flex Limited Daily Driver 1994 Taurus LX Project car 1986 Chrysler LeBaron convertible 2.2L Turbo II, modified A413 If you reply to this email, your message will be added to the discussion below:http://forum.garysgaragemahal.com/86-F150-5-0-running-poorly-tp55861p55908.html To unsubscribe from 86 F150 5.0 running poorly, click here.NAML https://ipmcdn.avast.com/images/icons/icon-envelope-tick-round-orange-animated-no-repeat-v1.gif Virus-free. www.avast.com Link to comment Share on other sites More sharing options...
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