Hi everyone this is my first post but i just recently purchased a 1990 f-150 xlt lariat 4.9 v6 with 6in lift and 31inch tires and before i even drove it i replaced rotor button,cap, plugs and wires,front and back brakes,fuel pump relay and fixed some vacuum leaks but on my way to work today it started running hot and bucking til it finally stalled. the check engine light lit up but went back off after a few seconds. i let it cool down for 20 mins and it fired back up til it got warm again and died. its acting like its out of gas but i kno its not can any1 help before this darn truck finds a new home:

 

The fact that it seems to be temperature related could indicate an electrical problem, but are you able to restart it right away after it stalls ?

 

it might be the coil ! once the coil gets too hot it can break down and shut the engine off !

 

As usual both hanky and bandit are on the right track. The problem you've discribed is an all too commen complaint. I have little doubt it's an electrical/electronic problem.

The ignition system used on your truck is a TFI module, Thick Film Ignition. It has a hall-effects distributor with a seperate coil.

First, probe the red wire terminal at the coil with the key in the On position. The test light should come on as this circuit provides battery positive to the coil.

When the truck will not start probe the green wire(s) with a test light. This time with the test light alligator clip connected to battery positve, and crank the engine with the key. This circuit is the switched circuit to the coil, and open and closes the ground. The test light should flash on and off.

Here is a pic of the coil, with connected wires.

http://fsjeep.homestead.com/files/TF...ade/coil_3.jpg

If the test light does in fact flash, and there is no spark comming out of the coil, the coil is bad.

If the test light does not flash remove, and renew the PIP, Profile Ignition Pick-up module.

The PIP is either located on the dist.. Here is a pic. It's that rectangle with a six wire connector.

http://breezeman.tripod.com/TFI_distributor.jpg

Or it is located on the radiator support, or fender well. These will have a heat sink. Here is a pic:

http://www.supermotors.net/getfile/8...nition-002.jpg

Here is a simplifed wiring diagram of the PIP module:

http://www.msextra.com/doc/ms1extra/...i-pinoutbg.gif

It is possible that the green wire #6 has no signal from the computer. However, a fault here usually results in a no-start condition hot or cold. This circuit can be tested with a multimeter. The meter should pulse when you crank the engine with the key. If it does not pulse then the computer is bad. But a doubt very much this is your problem. I've replaced more PIP modules than I can possible remember. Computers not so much for this complaint.

Hope to see another post from you. Writing these types of posts helps me to remember things, and it's always good to read some feedback.

Cheers.

 

I don't believe it makes too much difference if the test lite is connected to positive or ground because if connected to ground when you touch the other terminal of the coil primary if it doesn't lite , it shows the coil is open. And if it is connected to positive it shows you are getting a good ground for the coil to do it's job. Both seem to be good procedures, what do you think ?

 

Thanks for the help guys im going to have the truck towed home today and i will check it out. @ hanky it wont start right back up i have to let it cool down at least 20 mins before it will even think about starting again. might as well just replace both ignition module and coil to be on the safe side. i also believe its the coil ive done some research and it seems to be a common. good thing i live close to a pull a part.. thnks guys.

 

I think the reason it is recommended to connect the test light to positive is because the procedure is used to make sure the PIP module transistor is working properly, and grounding the coil. If you ground the test light it takes a microsecond or two for the magnetic field in the coil to collapse, and it tends to make the test light look like it's staying on all the time. Can't really see it flicker since it's completing the circuit from the coil, and not from the PIP.

 

Truck wont restart until it cools down some is a classic case of a bad PIP module. Good idea to replace the coil too. However, I highly recommend replacement of these componets with brand new parts. Based on empirical structure, the PIP module only has a service life of approx. 30,000 miles. Some even recommend renewal of the PIP as part of preventative maintenance.

If you do use a used PIP make sure you apply dielectric grease to the mating surface before installment. The d-grease acts as a heat sink and promotes longevity. A new PIP will come with some.

 

ok i checked both the ignition module and coil both checked good. so i broke out the chiltons book and come to find out my fan clutch was bad. so as a quick fix i took a piece of metal drilled a slotted hole in it , formed it to a L bracket then i took 1 bolt out of the fan itself bolted the bracket on then threw a few tack welds on the bracket and a bolt on the fan pulley so that the fan runs all the time. im going to try and get some pics up of my work if anyone wants to know how to do it.

 

You need to be careful when you start changing construction of fan parts. The reason is 'balance". If the fan assy is out of balance you will eventually ruin the water pump bearings and seal. Might want to reconsider if your steps have affected the fan system balance.