When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I just bought a 1986 F150 Super Cab Long Bed 4X4. My first truck!!! I am 45 but have always had to be "family minded." Kids are grown - time to play. The truck ran fine around town for about 200 miles or so. Now, you guessed it - my first truck problem. It will run great for about 5 - 10 miles or so until it gets warmed up. Then it will start hesitating under load. That progresses to idling rough and sputtering (both at idle and under load). It makes starting after the traffic light turms green difficult (I have to feather the gas pedal to keep it running. This in turn causes those behind me to blow their horns excessively (I'd blow back - but who can blame them???) Eventually no amount of feathering with my now tired foot will keep the truck from stalling. It will immediately start back up - but since it won't hardly move without stalling - restarting it becomes too depressing. Let it cool off and it will run great, warm up, and...well, you know. The truck is equipped with an "Emissions" light. This light comes on and turns off when I start the truck, but has never come on during the problem. I have the same problem regardless of which tank I am using. Any info to help me achieve my first truck repair would be greatly appreciated.
Is this fuel injected? If so, I would replace the module mounted on the side of the distributor. No guarentee that will fix it, but it does give a lot of heat related problems.
Thanks guys! I did a little look up on the TFI module and it does refer to the "thick film insulation" used to protect it from the heat coming from the engine and especially the distributor. From what I have read 77monster is also right about "too fragile ignition." Since the days I had no problems were colder (high around 40) and the days recently that I have had problems were in the 60s and 70s, the TFI module over heating is a very likely diagnosis. No check engine or emmission light coming on is also a symptom of faulty TFI. I will be out of town for a couple weeks, but when I get back I will do this easy and inexpensive fix first to see if it is the problem. I WILL let you all know. Thanks again!!!
I basically had the same problem with my 86. Would run fine until it warmed up, then is was a battle to keep it running. Feathering all the time, loss of power, same symptoms your having. I replaced lots of parts, fuel filter, pump..ect..ect....turned out to be the IAC. Even though it tested out fine electronically (via the haynes manual) and I cleaned it out with carb cleaner, it still turned out to be the problem. Its kind of spendy, but its worth looking at.