TheWeldingFords Posted June 29, 2023 Share Posted June 29, 2023 Hi Y'all, Recently while driving around when I come to a stop light the idle is jumping up and down from 500 rpm up to 1200 rpm and it just repeats that for a bit and then suddenly stops and holds at 1000 rpm for a bit and then goes back to surging. The second problem I have that I believe might be related is that when accelerating 1/3rd of the pedal or more it bucks and doesn't accelerate past that point in that gear typically happens around 3500 rpm and at some points if you floor it like that it might backfire(only happened twice to me) the other problem I notice is that its intermittent so sometimes I can use every bit of rpm i can get out of the engine and then the next time I go to do a hard pull and accelerate it'll buck. Any info on what to check this time would be helpful since I have 30 days before I drive 3000 miles to Alaska I replaced the TPS today with a Standard one just to see if it would help and it has not changed anything. I also upgraded to a PMGR starter today because when I went to drive back home from Orielly's my starter crapped out in the parking lot and decided today was the day to upgrade got a $350 starter for $60 (pretty happy with it, super quiet and powerful. Only problem I noticed is it hangs out for half a second after the truck starts and it makes a little bit of noise but goes away fairly quickly. Would a shim possibly fix this?) Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted June 29, 2023 Share Posted June 29, 2023 Alex, Have you got the solenoid jumpered, or did you run a trigger wire from the fender relay output to your starter and move the cable to be powered all the time? When your truck is bucking and backfiring have you checked to see if the ignition coil is really hot? Because those symptoms sound like a failing coil. I hope you can get Daisy running right before the big road trip. Â Link to comment Share on other sites More sharing options...
TheWeldingFords Posted June 29, 2023 Author Share Posted June 29, 2023 Alex, Have you got the solenoid jumpered, or did you run a trigger wire from the fender relay output to your starter and move the cable to be powered all the time? When your truck is bucking and backfiring have you checked to see if the ignition coil is really hot? Because those symptoms sound like a failing coil. I hope you can get Daisy running right before the big road trip. I just drove to work when I had the problem again and I felt the coil and it didn't feel hot just a bit warm from the engine bay heat. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted June 29, 2023 Share Posted June 29, 2023 I just drove to work when I had the problem again and I felt the coil and it didn't feel hot just a bit warm from the engine bay heat. Hmmm I suppose it's a step that you can eliminate the coil itself. The problem does seem more spark related that fuel related, though I'm no expert in these early EFI systems. Let's see what others have to suggest. Link to comment Share on other sites More sharing options...
Gary Lewis Posted June 29, 2023 Share Posted June 29, 2023 Hmmm I suppose it's a step that you can eliminate the coil itself. The problem does seem more spark related that fuel related, though I'm no expert in these early EFI systems. Let's see what others have to suggest. Yes, it sounds like ignition to me as well. And I'd guess it is the TFI module. The '86 EVTM shows the EEC controls the TFI module, and those are a known failure point during these years as most were mounted to the distributor. Later Ford moved them to the fender where they didn't get as hot, but wonky running or not running at all when hot is one of their symptoms. Link to comment Share on other sites More sharing options...
81-F150-Explorer Posted June 29, 2023 Share Posted June 29, 2023 Hmmm I suppose it's a step that you can eliminate the coil itself. The problem does seem more spark related that fuel related, though I'm no expert in these early EFI systems. Let's see what others have to suggest. Some suggestions ... ---------------------------------- The TFI-IV Ignition Module? Located on the distributor, and is prone for overheating. ---------------------------------- The Idle Air Controller (IAC) ? --------------------------------- Sticking EGR Valve? -------------------------------- Severe Vacuum Leaks? ------------------------------- PCV Valve malfunction or leak? ================== The EEC-IV / TFI-IV has a self Diagnostic routine. Both Key On, Engine off, and Running. First thing I would do is check the Self Diagnostic for codes to help narrow things down. Link to comment Share on other sites More sharing options...
81-F150-Explorer Posted June 29, 2023 Share Posted June 29, 2023 Yes, it sounds like ignition to me as well. And I'd guess it is the TFI module. The '86 EVTM shows the EEC controls the TFI module, and those are a known failure point during these years as most were mounted to the distributor. Later Ford moved them to the fender where they didn't get as hot, but wonky running or not running at all when hot is one of their symptoms. Great minds etc... Link to comment Share on other sites More sharing options...
Gary Lewis Posted June 29, 2023 Share Posted June 29, 2023 Great minds etc... I'll take that as a compliment. Link to comment Share on other sites More sharing options...
TheWeldingFords Posted June 29, 2023 Author Share Posted June 29, 2023 Some suggestions ... ---------------------------------- The TFI-IV Ignition Module? Located on the distributor, and is prone for overheating. ---------------------------------- The Idle Air Controller (IAC) ? --------------------------------- Sticking EGR Valve? -------------------------------- Severe Vacuum Leaks? ------------------------------- PCV Valve malfunction or leak? ================== The EEC-IV / TFI-IV has a self Diagnostic routine. Both Key On, Engine off, and Running. First thing I would do is check the Self Diagnostic for codes to help narrow things down. The IACV is about a month old, I haven't looked into the tfi module, I was thinking it might be related to that as I've read through the forum and mine is still distributor mounted. Any idea when I can get a kit to move it to the fender? Is it a decently easy job? I'm gonna pull up to the mechanic later after work and see what they say also, I'm gonna check timing again too and verify that it didn't somehow move on me. Link to comment Share on other sites More sharing options...
ArdWrknTrk Posted June 29, 2023 Share Posted June 29, 2023 The IACV is about a month old, I haven't looked into the tfi module, I was thinking it might be related to that as I've read through the forum and mine is still distributor mounted. Any idea when I can get a kit to move it to the fender? Is it a decently easy job? I'm gonna pull up to the mechanic later after work and see what they say also, I'm gonna check timing again too and verify that it didn't somehow move on me. The two places I know that used to offer TFI relocation kits/harnesses are Mcully Racing (the 5.0l Miata folks) and Fat Foxx. Link to comment Share on other sites More sharing options...
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